97 Cooling Mods and what else to beat the heat?

[Johnny B.]

Last month I upgraded to the dual t stat cross over, 190 GM t stats and new timing chain and gears. I just towed my travel trailer to the dealer yesterday 20 miles for its final warranty work. I didn't notice much change in engine temps since the upgrades. The outside temp was 65 and towing 6000 lbs. my temp gauge read 210 on the interstate at 65-70mph.

Prior to my upgrade 210-220 was a normal temp for the same condition with temps in the mid 80's. I believe one problem that I have is that I only have the thin 2 core radiator not the fat 4 core. It was replaced by the previous owner who probably didn't want to spend the extra $$$.

What else can I do, new fan clutch, fan and which ones?

[cruzer]

Johnny B, I just did cooling mods on my 92 GMC
this spring along w/rad, 20" fan and clutch.
Ref a recent past post "heating up at idle"
I ref what I did. I rarely get over 200*. The 20"
fan requires a new fan clutch. I see you have
93 which should have a 6 blade fan and a different bolt pattern than the late models.
The clutch I purchase was a GM and it kicks in at 197*. From what I read in past post this seems
early for a GM clutch. Maybe I got lucky on that.
Kennedy and Hayden(Heath Diesel) sell clutches actually designed to engage earlier than 210*
When I was shopping on rads the only 1's I found
were 2 row and 1 row aluminum. Be sure to keep rad/conderser and coolers bug free. I found a lot of junk between componets.Hope this helps.

[rjschoolcraft]

I used the kennedy clutch and 20" steel fan blade. I, too, did the dual t-stat and HO pump first and was disappointed by still having overheating problems. It appears that the full system, including the fan and clutch, must be upgraded to be successful. Now my temps stay in check and I think I have the problem licked.

[Johnny B.]

Thanks for the replies guys ! Looks like I'll be adding a new fan and clutch. I remember reading an article on the Duramax fan and I believe a 98 6.5 clutch, any recommendations?

Any thoughts on removing the fan and clutch and converting to electric fans? I've seen dual fans for around $450.

[ucdavis]

Johnny,
Lotsa discussion a while back on electric fans. No fans identified w/sufficient CFMs to provide the cooling we need.
I bought the kennedy clutch w/9 blade metal fan. General concensus is that its about equivalent to the Dmax fan. If you do the latter I believe you need a late model clutch for a drop-in solution (bolt pattern on Dmax blade & maybe ID is different if I recall correctly).
I've taken some measurements on the 9-blade fan to do rotational inertia comparison to Dmax, just for fun; now I need a Dmax blade to do measurements & weights on it. This is to claculate the relative efficiency loss from fan weight, but I suspect it is nominal vs. the positive effects of the lower fan clutch curve (kennedy-180* or Hayden-190*). The real trick is to get the CFMs up sooner when you're pouring the coals to her.

[Johnny B.]

ucdavis, I suspect your correct on not finding a capable electric fan. I don't have a heat problem at 55 mph on the interstate its only at the higher rpm's under load at higher speeds. I have no doubt that more CFM and a clutch engaging the fan sooner would correct the problem. I guess it gets down to which clutch and fan to get. Thanks!

[Turbine Doc]

In addition to previous recommendations you might want to think about a second trans. cooler, deeper trans pan, bypass oil filt set up. Trans running cooler will help with heating probs, as it is cooled by engine radiator/coolant removing/reducing trans. heat load will help.

I installed a DeRaile electric fan remote cooler under the bed from Summit racing, thermostat controlled to come on at 180F pan temp, PML [www.yourcovers.com[/URL] has cast alum pans for extra 3.25 QT trans fluid more fluid to try to heat up. Trans pan temp. never over 160 when running empty 140-150 about norm, have yet to see over 170 towing 10K gooseneck loaded on few short hauls made since installing.

Bypass filt set up does more than clean engine oil, also gives more oil in system to heat up about 3 qt over stock depending who's filts you use; I use Baldwins, some passive cooling there as well, as filters usually located further away from engine heat than stock location, and cooler air on filt bodies pulling some heat away, probably minimal but every bit helps.

Those were the semi low dollar mods, for high dollar 1st go with better flow exhaust, if you don't have them gages are a must so you know when to back off, then Intercooling.

200+F reduction depending on current ambient temps. to what leaves the turbo and fed to the engine, not inexpensive but if you want low temps only way to go. check out my installation

bear with me on the site still learning the web maker thing

http://myweb.cableone.net/tbogemirep/TBOGEMIREP%2098%20GMC.htm

[StephenA]

The dealer wanted 400 bucks for the fan clutch for my 92, but after some research, I went with the 97-98 clutch and the 21" Dmax 9 blade composite fan for under a hundred bucks (www.gmpartsdirect.com)!. The flutes on the fan are deeper as well as more numberous, but overall the thing fit into the cowling with no mods necessary (I was prepared to insert an inch spacer between the top & bottom cowling where they join halfway down on each side of the radiator, but it wasn't necessary, & the closer tolerances just move more air). All in all, it cools much better, the engine spins up easier, & the fan noise is NONEXISTANT even after the clutch engages fully. My hood noise went down by 2/3s! The 97 clutch is a direct bolt on using four of the old fan bolts. So far, I'm very happy. The low mass fan doesn't seem the be stressing the water pump as much as the heavy stock steel fan did, and it moves more air more efficiently with less wasted turbulance (hense the low noise), so I doubt it's loading up the components on the serp belt to an early demise.
Could be just the ticket for you, too. I plan to rod my rad & add Kennedy's pump, stats & crossover soon, but in the meantime my temps are already vastly improved.
Good luck
Stephen

Here's the data from GMPartsDirect:
-their shipping is a bit high, but the prices are usually fantastic.

Duramax 21" 9-blade 21" composite fan-
GM PART # 15010202
CATEGORY: Engine Cooling Blade
PACK QTY: 1 CORE CHARGE: $0.00
GM LIST: $53.19
OUR PRICE: $30.32

1997 Fan Clutch-
GM PART # 15022302
CATEGORY: Engine Air Cooling Fan Clutch
PACK QTY: 1 CORE CHARGE: $0.00
GM LIST: $100.36
OUR PRICE: $50.18
DESCRIPTION: CLUTCH

[HowieE]

Johnny B

You have spent a bit of money on your modes todate why haven't you changed that radiator. If you don't provide a means of removing heat,ie the radiator, all the fans, stats, and pumps won't provide the results.
I pull 10,000# and hold 185 degees without AC and 190 with the AC on. Take a look at my web site to get an idea of what may be effecting the overall situatiion.

[Johnny B.]

To answer some questions, I did add a second trans cooler after the 97 cooling mods. The second one was a new OEM GM trans cooler found on Ebay for $24.99. It was a tight fit with both coolers, they are strapped together my only thought is that they might not get sufficient air flow through them, I'll watch my gauge and find out.

I plan on updating to a Diesel Depot down pipe when I get the cooling situation remedied.

My radiator appears to have good flow. I also cleaned the fins and replaced the A/C condenser earlier this summer. I used the shop vac on the radiator then soaking it with simple green and gave it a good washing. I repeated this again last month, not really dirty just a few bugs.

StephenA , are the 21" fan and 98 clutch a direct bolt on to my existing water pump studs?

If so this appears to be my next step and hopefully the solution.

Thank you all for the tips and information, my $20 membership was well spent!

[StephenA]

Hi Johnny, Yep- the 97+ clutch with the part number I listed is a direct bolt on to the water pump using the same bolts that hold your old clutch in place. Then use four of the old fan bolts to attach the 21" composite fan. If the cowl is too close on top or bottom build a spacer, but I didn't need one. Left & right tolerances have to be shaved or ground, but mine needed no modifications at all. Good luck, let me know how you like the combo.
Stephen

[tanker]

Johnny B, Howie E. is correct about that radiator, Get a big one as is standard for your application. I have 4 trans. coolers and one is a 12-V fan cooler. Keeping as much heat out of the radiator is also a key factor. I also have a "BD" Torq-Loc and their exhaust brake. The Torq-Loc keeps my converter locked up even in 2nd gear, over 35mph which keeps transmissions temps real low. The 12-V fan cooler along with the other coolers, drop my trans oil temps by almost 100*.(I have two sending units w/one gauge, one the inlet & outlet cooling lines). Kennedy's clutch and the composite D-Max fan is also a great combination. Howie and I both tow and teamed up this past year on a cross-country trip that took us from the East Coast, to Arizona, then up to Montana for the "Rendezvous". My temps never went above 200* even on the hardest pulls up over 13,000ft. Most times I'm at 185* to 190* when towing, which is a far cry from what I was when my truck was new. I'd make the radiator your next step. ;)

[piersbc]

I'm looking at doing the 21" duramax fan with 97 clutch modification to my 95. Does anyone know how the 97 fan clutch is different than my 95 fan clutch? I'm assuming that the 97 clutch kicks in/out at a higher rpm...and with the 9 blade fan it moves more air...

[Kennedy]

There is only one clutch that engages earlier than stock, and that one is specifically built for Kennedy Diesel. Hayden does not mfr clutches in this size range, they simply purchase from Borg Warner which is the mfr of the OE units AND the KD units. The KD unit is pec'd to engage at 180

[piersbc]

[b]The KD unit is pec'd to engage at 180

[rjschoolcraft]

The fan clutches engage using the principle of viscous shear. There is a silicon fluid inside the clutch hub. A valve is opened and closed by a bi-metallic coil on the front of the clutch hub. When the valve opens, fluid is introduced into the clutch body where a land and groove arrangement creates very small clearances that the fluid tries to fill. The viscosity of the fluid causes drag which is the motive force to turn the fan. The position of the valve opening in the hub coupled with the properties of the bi-metallic coil determine the temperature at which the clutch "engages" and "disengages". The coil senses the temperature of the air that has passed through the radiator. That is the temperature that Kennedy was referring to.

Kennedy's clutch is the only one that I'm aware of that is specially calibrated to engage at a lower temperature than the OEM unit. Others make claims, but they do not hold up to scrutiny.

[More Power]

For a bit of trivia... The 1994+ aluminum radiator and fan shroud fit the 1993 and earlier radiator core supports. These aluminum radiators utilize a taller, higher capacity core. That's why a matching fan shroud is necessary.

The newer style fan shroud is cheaper than you think, and is more robust than the earlier versions.

The question is: Is a 5-row core copper/brass radiator (like that used in TDP's Project) more thermally efficient that a taller aluminum radiator? I've read persuasive pros & cons for each at several places on the web. Still don't know.

Jim

[gvig]

Johnny B., I just did the cooling mods, dual T-stat crossover, D-max fan, and an OEM clutch. I used dual Stant 180 degree t-stats. Normally I would be running at 180 around town but now the temp goes up to 160-165 and stays there. Haven't been able to force it up yet.

I had the original fan (6 bolt) from my 95 so I had to get a new clutch to go with the fan. I couldn't swing a Kennedy or a Hayden (Borg actually) so the OEM was the only option enabling me the 4 bolt fan mounting.

On Wednesday I will find out what works or not as I will be pulling out with my fifth wheel heading west. If it doesn't heat on nine mile hill west out of Albequerque I will be very pleased. Last time on that hill I ended up on the shoulder, second gear and moderate throttle, driving by the temp gauge not the speedo or tach.

[jspringator]

I tried to use the Kennedy fan clutch, but mine was a late 99 with a screw on style fan clutch, which JK does not support, so I had to return it. After my latest trip, I wish I had replaced the water pump with a high capacity bolt on design when I had the chance so I could have used Kennedy's clutch. Anyone know how to hack the thermostat on those things?

[rjschoolcraft]

George,

I wish you well, but my experience says you'll still be in trouble. The Kennedy clutch was the last piece of the puzzle for me in the cooling quest.

James,

Some have tweaked the spring with success. However, the results are not very repeatable. Your best option would be to put a 98 pump on your engine and use the Kennedy clutch. I think your fan is the same P/N as the one I'm running (but should verify that). If it is, it will bolt on to the Kennedy clutch and work very well.

Did you have problems with the Hayden unit?

[ 12-26-2005, 05:20 PM: Message edited by: ronniejoe ]

[rjschoolcraft]

Originally posted by More Power:
The question is: Is a 5-row core copper/brass radiator (like that used in TDP's Project) more thermally efficient that a taller aluminum radiator? I've read persuasive pros & cons for each at several places on the web. Still don't know.

Jim Jim,

I'd go with the copper/brass as being more efficient. The main reason that the later aluminum radiator is taller is because of the reduced thermal conductivity (to the tune of 40% lower) of aluminum compared to copper. The entire reason for switching to aluminum is cost, pure and simple. It certainly was not for cooling performance. :mad: I'd also wager that this is the reason that the square holes were added to the bumper for the 6.5's. IIRC, the switch from copper to aluminum happened right about the same time as the introduction of the 6.5.

[tehillah1]

I just got done replacing my heater core to fix a leak only to find that the water pump is dripping as well...From what you all are sharing here it looks like I can use a later model ('97-'99) water pump on my '94 6.5 and increase the water flow. The newer units will bolt up? I'm thinking of doing the Duramax fan upgrade while I have everything apart...

[gvig]

ronniejoe,

Those square holes in the front bumper may be there for cooling but for those of us with short legs they are a great equalizer when it comes time to climb into the engine compartment to reach something near the back like changing the fuel filter. If they weren't there I would have to fire up the hot wrench and create them.

[jspringator]

RJ, no problems, per se, but last trip out I had to back off the throttle due to heating concerns while trying to go 65 on I-10 in FLAT Florida (3 clicks or so over 210)in October. I tend to believe what I have read that they don't engage sooner, but I don't know for sure. I lost my diverters from the bumper holes.

Realistically,the cure to my problem would be to remove the grill unbolt the various coolers and scrub them with a brush. I should do this first.

[ 12-27-2005, 05:12 PM: Message edited by: James Springate ]

[tehillah1]

Can I put the newer '96-'99 water pump on my '94 6.5 without installing the dual thermostat crossover? Where can I get a 180 degree thermostat for this truck?

[rjschoolcraft]

It is not recommended to install the HO pump without doing the dual thermostats. Some have, but there have been consequences.

[tehillah1]

Ron,
Thanks for the warning. What kind of problems might I face? Is there anything else I should be looking at before upgrading the cooling system? I thought about doing the Duramax fan upgrade as well, maybe I should stick with stock until I'm ready to do it all...

[rjschoolcraft]

If you plan to tow heavy...

Late model HO pump, dual t-stat crossover, Kennedy fan clutch and 9-blade steel fan. The Kennedy clutch was designed for the steel fan and the Borg-Warner engineers say it's best to use what was designed. Some have run the D-max fan with the KD clutch and reported good results, though. I use the 9-blade steel fan. Next...INTERCOOLER. I cannot emphasize that enough. With that in place, the Kennedy chip will make the truck go. You won't believe it.

If you're only running solo, the cooling mods should still be done, but the intercooler is less necessary.

As for the HO pump without the dual crossover...GM reported blowing out freeze plugs during early development testing. That is why they changed to the dual T-stat crossover. If you do a search on the subject, you'll see lots of discussion.

[Cowracer]

In addition to the standard '97 mods, I did this.

Split Flow Cooling Mod (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=008947)

I have been running it for 2-3 months now in daily driving with no problems. I have not run any tests on this set-up yet, it was past the hot part of the year when I got the truck running.

Next 100 Degree Day (probably in March in missouri :D ) I plan on documenting the effects.

I finally figured out a non-invasive way to monitor head temps across the entire head.

I belive my system will work, and I plan on proving it next year.

Tim

[grape]

Originally posted by ronniejoe:

As for the HO pump without the dual crossover...GM reported blowing out freeze plugs during early development testing. That is why they changed to the dual T-stat crossover. If you do a search on the subject, you'll see lots of discussion. what about when the truck is cold and the thermostats aren't open yet?

[rjschoolcraft]

All I'm doing is repeating what GM reported. I make no claims as to the veracity of the information. I won't take the bait...

[tehillah1]

Wow, that's some serious pressure that would blow out a freeze plug and not a hose or two! I'll take the advice and get the dual t-stat crossover and do it d.i.r.f.t. (do it right - first time.

[Kennedy]

Originally posted by tehillah1:
Wow, that's some serious pressure that would blow out a freeze plug and not a hose or two! I'll take the advice and get the dual t-stat crossover and do it d.i.r.f.t. (do it right - first time. We've got everything that you need for 6.5 cooling ;)


As for the frost plug thing, I know there are a lot of skeptics, but after seeing the pressures at the discharge of a Dmax water pump I can see how it could happen. The pressure gauge was a 30 psi/30" hg. unit and I could swing it around into the vacuum scale at will...

[rjschoolcraft]

For Grape,

I went down and pulled my old single t-stat housing off the shelf for comparison. The new dual-stat housing has significantly more flow area when the stats are closed. Also, the bypass is open all the time, whether the t-stats are open or closed. The old housing uses a t-stat that closes off the bypass when it opens fully, forcing all the flow through the stat. When the old style stat is closed, there is only about .250" clearance between the valve and the seat. This causes significant flow restriction.

One might improve the situation by using a new style stat in the old housing, but there still is advantage to the new housing.

So, the recommendation is still to do both the pump and crossover at the same time.

I'll post some pictures later. FWIW.

[ 12-29-2005, 05:22 PM: Message edited by: ronniejoe ]

[sturgeon-phish]

What about the no added water coolant? I went to the Evans Cooling website and did some reading. It looks interesting. Running at a lower pressure (~7#) and using high flow T-stats may be something to look into. This may be good for anew thread. Anyone used the stuff yet?
Thanks Jim

[Kennedy]

Lower system operating pressure is of no real benefit. The pressures seen are a result of flow. Evans coolant isn't necessarily a bad idea, BUT it will not be as effective as a 50/50 glycol blend. The key feature of Evans is resistance to boiling/microboiling.

P.S. If you do run Evans there is no need to reduce or eliminate pressure...

[gvig]

Ronniejoe,

I just arrived in Cailf. The hill west of Alb. was no problem, did not even get to 180. However the hill south of Camp Verde did drive it up to about 195, but that was it. When the clutch engaged the temp held for a sec and then started back down.

Just pulled a grade of about 20% for a half mile, very steep drive, couldn't make more than 4-5 mph full throttle in first gear. Temps went up to maybe 195 and the fan clutch engaged and the temps started back down. It appears for my application I have a solution though the next piggy bank will have "INTERCOOLER" written on it.

Truck at 440K+/engine at 270K+ and used one quart of oil in the last 1300 miles pulling hard. Truck plus trailer right at 14K. I am amazed and blessed!

After I get the most out of the current configuration I will look at a chip and that will no doubt start a new saga.

[rjschoolcraft]

George,

Sounds great! What was the outside air temperature?

[gvig]

Ronniejoe,

Ok, you got me on that one. The outside temps were in the mid 60's yesterday on I-17. I will get to really test my system in May when I make the return trip. I am sure that with temps in the low 100's the story may be different but under the conditions yesterday I would have had a big problem in my old configuration. There is no doubt when the clutch engages.

The temp here in Banning where I pulled the "impossible" driveway was in the upper 70's. I will try in the next day or so to accurately measure the grade. I gotta know, just for me anyway. I'll let you know.

[rjschoolcraft]

George,

Sounds like you're making good improvements. I've been on the shoulder with flashers going crawling at 20 mph before, too... Not fun. Pulled the grade from Lone Pine, CA up to Whitney Portal. Eleveation changes from about 2000 ft to about 8600 ft in 15 miles...most of that in the last 5. Had to use low range and pull over several times to cool back down. I'd like to go do that again now and see how things work.

For Grape,

Here are some pictures (as I promised) of the thermostat housings.

This picture is of the new dual t-stat housing with the outlet cover removed.

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM001290.JPG

Here is a close up of the inside of the housing.

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM001291.JPG

Next is a picture of the old housing that was original equipment on my 95.

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM001292.JPG

A close-up view of the inside of the housing.

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM001293.JPG

A shot of the original equipment thermostat.

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM001294.JPG

This last photo is a shot of the old housing looking up through the bypass port. Notice how much the bypass close-off valve restricts the flow area.

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM001295.JPG

As you can see, the new dual t-stat housing improves flow when the t-stats are open and when they are closed.

Hope this helps. ;)

[20050627|3|008327|000043|65.183.99.20]

Soooo.

If a guy has put on a newer water pump, is someone willing to sell just the dual thermo housing? Maybe along with a lower temp clutch fan?

I plan on the clutch before towing season (don't have any overheating problems right now) but am thinking the housing may be a good idea too.

[GMC Hauler]

There is something I want to point out here. There are two main differences with the old style and new style thermostat housings. The main and obvious first difference is 2 thermostats vice 1. The second difference is the different type of thermostats and how it affects bypass flow.

John has spoken about freeze plugs blowing out on the blocks because of high flow water pumps without the dual thermostat crossover. If switching the crossover fixes this potential problem, then what are the differencs between the two?

Notice in Ron's fourth picture, the machined area is where the bypass valve interacts. It acts as an orifice plate. If the orifice plate was removed and thermostat type was switched to a model without the bypass valve, there would be no difference (not considering 1 vs 2 thermostats) as both types of housings have to go through a 1" hose to the water pump (note picture one does not have an orifice plate). Remember, when the engine is not up to temperature, the thermostats are closed and don't contribute to flow. All flow is through the bypass.

In theory, you could take an older type of thermostat housing, switch thermostat types, grind away the orifice plate, and should have no problems using the high flow water pump. This variation should prevent the blowout of freeze plugs, provide increased flow through the block as GM states with the high flow pump and dual crossover, and some increased flow through the radiator(although not quite the 9% if I remember correctly) that GM states with both parts.

If I was a betting man, I would bet that the freeze plug blowout was happening when the block was warm and the thermostat opened. That caused a great restriction, causing flow to greatly decrease and pressure to spike high at the outlet of the water pump.

For note, I have the single thermostat crossover, but it is a hybrid between Ron's and the new dual thermoatat. It looks exactly like the dual model except.... 1 thermostat. I noticed these things when I had my crossover off.

[Kennedy]

The simple (best) answer is to install the cooling mods upgrade as illustrated by MP in the 1998? Feature articles. These parts are offered in kit form by DP vendors like myself and include all you need and the best quality components available...

[gvig]

Tacklewasher,

I don't want to take any business from DP supporters like Kennedy or Heath but I too am on a budget that is at time almost non existant. I bought my T-stat crossover from a local Chevy parts house using a buddys shop account. The crossover was right at $100 and the cover was right at $50. I used Stant 180 degree thermostats and this setup works for me for now. I went to a local fastener warehouse and bought cad plated metric socket head cap screws to hold it together. Got the gaskets at an O'Reillys. My fan was the infamous 6 bolt setup for 95's and so I had to buy a fan clutch to be able to use a D-max fan. Couldn't swing a good one from Kennedy so I bought a stock clutch from the same Chevy parts house at a good price. If I had the money I would have gotten the clutch from Kennedy and would have been better off for it.

Above all, buy the best quality you can afford, you won't be sorry.

[gvig]

Ronniejoe,

FYI, with reference to my earlier post, I just got back from measuring the grade on the drive into here. It measures right at 24 per cent grade for about one eighth mile. The rest (mostly) at the top and the bottom is slightly less than that. And no running start, you make a very short radius ninety degree turn, get the fifth wheel straightened out and then you are on the grade. Good test of transmission clutches, driveline, engine torque, and pucker factor.

[rjschoolcraft]

That's pretty steep! :eek:

[dieseldummy]

For the record I ran a HO water pump w/single stat for around 20K with no problems. That was on the origional freeze plugs with a total of 140K by the time I upgraded to dual stats. I think the old line about the freeze plugs blowing out is purely a marketing scheme for some... Looking back on things now I wish I would have stayed with the single stat setup and not modify my throttle bracket.

[Kennedy]

MP did not and does not market the cooling upgrades pkg, only reported the benefits. He also (if memoruy serves) first mentioned the potential "soft plug" issue.

We did also have a party here (again if memory serves) pop out a couple of block heaters...

[rjschoolcraft]

Originally posted by dieseldummy:
I think the old line about the freeze plugs blowing out is purely a marketing scheme for some... Cynicism is something that we all indulge in now and then. It's also fine for you to have whatever opinion that you want. Let's just try not to blur the line between fact (as seen in the photos posted earlier) and opinion (wishful thinking, in many cases).

I, too, recall reading about block heaters popping out when running the HO pump with single stat crossover.

In reality, one can find anecdotal evidence to support just about any position that he chooses. However, the facts are these: the new pump flows more coolant than the old pump (impeller is visibly much larger on the new one); if nothing changes, this will result in higher system operating pressure (simple physics, to flow more volume through a particular hole, the pressure must increase); GM designed a new cross over with significantly improved flow area both in bypass and through the thermostats to the radiator and the pump and new housing were implemented as a package. Many, many people do things all the time that are contrary to very reasonable recommendations, sometimes with disastrous results, sometimes successfully. As always, the choice is yours.

After initially posting this, I did a search and found this thread about a block heater popping out. (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=006871) I made a post that referenced an article that More Power wrote regarding this issue. That article was in the 1998 book, but I don't know where it is now. Here's a quote, "Two different GM sources have reported that during the test phase of the prototype high-output water pumps, a single thermostat contributed to pressure pulses that caused coolant cavitation in the water pump and blown soft plugs in the engine block."

If you still want to think that this is a marketing ploy, be my guest. However, it is not supported by the evidence.

Edited to fix a spelling error.

[ 01-03-2006, 08:01 PM: Message edited by: ronniejoe ]

[dieseldummy]

I never recalled seeing the post by Jim P stating he lost a block heater. It still seems to me however that there are/were alot of us that ran/run the HO water pump with a single stat. I'll just leave it at this RJ because we all know that arguing with you is like talking to a brick wall... Just ask Grape...

[rjschoolcraft]

:D

I know, it's hard to argue with facts. When you have facts on your side and are right, why give in?

Actually, if you want to run whatever you want to run, I don't care. My concern with you is over the "marketing ploy" comment. I thought that was underhanded and unnecessary. I decided to set the record straight.

You brought up Grape...

He made one of his cryptic comments earlier in this thread. Once again, I provided data to support my position and he hasn't been heard from since.

Make up your own mind.

[jspringator]

Got a little overheating last trip. I'm changing out my thermostats and going to clean my radiator and other coolers. BTW, someone, in blue magic marker, drew this on my thermostat housing .X. What in the world does this mean?

[tehillah1]

I just did my water pump...put the stocker in until I can pony up for the whole cooling upgrade. The pics certainly do speak a volume in my mind, RJ...bigger pipe = more flow, less pressure. I'm for erring on the side of caution. My luck would be to be the guy reporting the blow out of a block heater or freeze plug 50 miles after putting the HO pump on without the rest of the package that goes with it...

[AndyL]

I have no data but I find the idea of blowing out freeze plugs hard to believe. I would think coolant would start to ooze/blow out the gaskets from the crossover or rupture the bypass/heater hoses way before the freeze plugs.

One other thought is that much flow could possible hold the thermostat closed creating excessive pressure. My bet is still the gaskets or hoses first.

I have removed dozens of freeze plugs in my day, they are usually stuck in there pretty good!

[GMC Hauler]

Originally posted by James Springate:
Got a little overheating last trip. I'm changing out my thermostats and going to clean my radiator and other coolers. BTW, someone, in blue magic marker, drew this on my thermostat housing .X. What in the world does this mean? You got overheating with the cooling mods and an intercooler? What are the details?

[jspringator]

Didn't have the intercooler then. Coolant Temps 2-3 clicks above 210 on I-10 between Lake City and JAX, trying to maintain 65 MPH, towing a 9,000 trailer with 6 people in Sub. I just slowed down until it went back to 210. Held 55 no problem. I just want the truck to be able to maintain 65 on mostly flat ground with EGT'S below 875 and Coolant temps below 210. I am trying to cover all my bases so I won't have to worry about it next time. I wonder about the condition of the radiator with this many miles. Of course, it is likely the intercooler will solve my problem.

[GMC Hauler]

My recent towing experience last August almost echo's yours: 9000 lb travel trailer (8500 plus gear), 4 people, 2 dogs. I had temp's swing between 200 and 220 while towing in direct, 900-1050 EGT 55 to 65 mph. When I was able to get her into overdirve, temperatures were more stable 195-210, 850-950 EGT, 75 MPH, Coolant temperatures more or less stable over a 5 minute period. I used less fuel in OD at 75 versus direct at 55. That was determined by fuel pressure going into the injection pump (pressure was higher in OD). I don't have the cooling upgrades, except for a fan clutch and duramax fan. Outside temperatures were 90 degrees. Hills were a different monster, though... I was limited by EGT, which I maintained <1100, with only ocasional hits at 1150. I had plenty of pedal to go, although I never overheated.

The biggest thing I found is that everything was better in OD between 70-75. I wasn't expecting that.

[markelectric]

I have two things to add.

I for the last year and a half have run a high output pump on the 95 Sub with no other mods than a 180 stat which doesnot have the lower part. Block heater and freeze plugs are fine.

I am also of the opinion that a 94 stock cooling system will cool any heat that can be created with these engines chips or not. The system needs to be clean to do it. I had overheating problems on a 94 while trailering. I thought the fan clutch would be the majic fixall. I bought one and was not impressed. Bill Heath pointed out that the radiator needs to be clean inside and outside. After having the radiator cleaned I could tow 16000 lbs on a 100 degree day with the AC on full tilt and hold 190 degree coolant temp all day long. MY opinion (just mine) is that the crossover and HO pumps are a band aid fix to other problems. I also think these trucks need easy drains for the coolant and banjo style couplings to be able to pull the radiator anually for proper cleaning.

I will now put on my nomex skivvies.....FLAME AWAY

[grape]

LOL, look what i've started now........ smile.gif

Isn't the heater circuit another bypass valve that never closes flow from the engine back to the radiator.

[rjschoolcraft]

Yep.

You can lead a horse to water... ;)

[GMC Hauler]

Originally posted by ronniejoe:
:D You brought up Grape...

He made one of his cryptic comments earlier in this thread. So do you, Ron.


Originally posted by ronniejoe:

You can lead a horse to water... [Wink]
Originally posted by dieseldummy:

I think the old line about the freeze plugs blowing out is purely a marketing scheme for some... [Wink] While you may be able to modify a single stat crossover to near the performance of a dual stat model, it's hard to tell what was going on behind the scenes with the engineers. I don't doubt that some freeze plugs were blowing out, more than acceptible for their QA program. While it's your opinion, you are still entitled to it. I ensure that every day.


Originally posted by kennedy:
The simple (best) answer is to install the cooling mods upgrade as illustrated by MP in the 1998? Feature articles. These parts are offered in kit form by DP vendors like myself and include all you need and the best quality components available... You are right. It is easier for the average guy to just install the new one and not modify the old one. If the guy grinds too far on the orifice plate, it could spell disaster. The new model also sends the most flow to the radiator.


Originally posted by ronniejoe:
All I'm doing is repeating what GM reported. I make no claims as to the veracity of the information. I won't take the bait...We all agree that this is what GM repoprted. Sometimes, GM is not always right, and the approach they take is not the best or cheapest. Remember, they are the ones that gave us these problems to begin with. Sometimes it is due to unforseen circumstances and beyond their normal testing program, sometimes it is due to other than honarable intentions.


Originally posted on the homepage:
Our membership program also helps each of us share a common interest and learn from each other.And...


Originally posted on the homepage:
This is not a General Motors Corporation web site, nor are we diesel mechanics. In addition to nineteen years of GM diesel pickup ownership, our qualifications come from broad-based technical training, professional automotive writing and photography experience, and a desire to learn more about the GM diesel engines.This is an exchange of ideas, no matter how flawed they are sometimes. That is what makes this page great. We exchange ideas, and politely point out flaws. If the person doesn't choose to follow, we don't criticize. Click on this link to see how a similar situation was handled: Moondogie AC Recovery Question. (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=009002#000001)

Let's leave the fighting in Iraq and not on the board. We're all adults here.

Humbily yours,

Roger, AKA GMC Hauler

[nvmtnlion]

Eloquently put Roger! Thanks, I couldn't agree more.


Originally posted on the homepage:
This is not a General Motors Corporation web site, nor are we diesel mechanics. In addition to nineteen years of GM diesel pickup ownership, our qualifications come from broad-based technical training, professional automotive writing and photography experience, and a desire to learn more about the GM diesel engines.
This is an exchange of ideas, no matter how flawed they are sometimes. That is what makes this page great. We exchange ideas, and politely point out flaws. If the person doesn't choose to follow, we don't criticize. Click on this link to see how a similar situation was handled: Moondogie AC Recovery Question. (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=009002#000001)

Let's leave the fighting in Iraq and not on the board. We're all adults here.

Humbily yours,

Roger, AKA GMC Hauler

[ 01-03-2006, 02:15 PM: Message edited by: JohnC ]

[dieseldummy]

Here is something else I've been considering about cooling systems lately; Some large trucks are moving back to low psi low flow cooling systems, I see it as a move to help meet emissions by keeping more of a constant temp, but it apparently is able to keep 550 HP engines cool. Would it work on a 6.5?

I appologize for having a difference of opinions earlier in this thread. I just get tired of the same old things like telling people to just do the whole thing at once or do it once the right way and ect. There are those of us out there that like to tinker and try new things, we might not have an engineering degree, but keep in mind it was engineers that made the 6.5 the way it is... I'm still a firm believer in the theory of if it works then that's all that matters. I just can't wait to see what fancy turbo upgrade RJ has come up with to better all of us that have tried other things.

[GMC Hauler]

Originally posted by dieseldummy:
Here is something else I've been considering about cooling systems lately; Some large trucks are moving back to low psi low flow cooling systems, I see it as a move to help meet emissions by keeping more of a constant temp, but it apparently is able to keep 550 HP engines cool. Would it work on a 6.5? Maybe it's also an effort to increase MPG???

Maybe an effort to reduce thermal stresses in the block (lower delta temperatures across the water jacket to piston/combustion chamber)????

[G. Gearloose]

Originally posted by grape:
LOL, look what i've started now........ smile.gif

Isn't the heater circuit another bypass valve that never closes flow from the engine back to the radiator. Good point! actually it never reaches the radiator on the modern 6.5's, it goes to nipple on the lower radiator hose and back into the engine. Wasted volume.

I suspect at under full heat stess, a shutoff valve on the h-core loop could improve total flow across the radiator when the tstats are open; but when they ae closed, can the by-pass handle the total flow at high revs all by itself?

[rjschoolcraft]

The heater circuit is the same in both cases. It has no impact on the discussion at hand.

Cheerio! :cool:

[grape]

I have another dumb question, how come the engines that blew freeze plugs out didn't overpower the radiator cap? Isn't that about 14psi with a smaller diameter of course. I've sure seen alot more trucks puking out the overflow tank than I have the freeze plugs. Anybody else have their freeze plugs come out without ever moving water into the overflow tank? :confused:

[grape]

Originally posted by dieseldummy:
I just can't wait to see what fancy turbo upgrade RJ has come up with to better all of us that have tried other things. Don't need any more turbo.........just up the boost with the same crappy wheel, boost is boost, ask RJ He'll fill you in.

After all, he did make 225 hp to the rear tires before it blew up............he seems to be an expert, just ask him LOL.

[Kennedy]

Originally posted by grape:
I have another dumb question, how come the engines that blew freeze plugs out didn't overpower the radiator cap? Isn't that about 14psi with a smaller diameter of course. I've sure seen alot more trucks puking out the overflow tank than I have the freeze plugs. Anybody else have their freeze plugs come out without ever moving water into the overflow tank? :confused: You have to understand the flow dynamics of the system. The rapid flow of coolant with no place to go puts pressure inside the block and heads. This is highest at high RPM's which may explain why some have gotten away with the big pump on the single stat as driving styles differ.

[dieseldummy]

I can tell you right now that my driving style used to involve lots of rpms while pulling a trailer. IMO it doesn't get much worse than that pressure wise... Here is another thing to consider; If the HO pump moves so much more than why don't we have cavitation issues? I mean when the stat is closed all that pressure is being made and at a certain point no more water can flow through the pump so the pump just has to be aggitating the water since it has no where to go. Another point; has anyone done an extinsive study on the impeller of the HO water pump to determine if it does indeed make more psi than the standard one? Just because it can flow more GPH when the stat is open doesn't mean that it actually makes more PSI. Typically high psi pumps are gear pumps or piston pumps, not your standard impellar pump. A good example of this is a typical gas powered water pump. It will move X amount of GPH at so many feet of head which usually equates to low PSI. At a higher amount of head ft it will flow alot less. During both situations it will only make X amount of PSI because that is just the nature of the beast.

Pick all of this apart, I know someone will. It's all based off of my REAL WORLD EXPERIENCE nothing more since I'm just an un-edumacated high school grad... :eek:

[Kennedy]

I believe the key words by MP were: "Under certain operating conditions"...

You know what I think people are missing here is the idea that GM supposedly added these mods in an effort to improve circulation in the block and eliminate/reduce stagnation. Increased pressure also helps keep the coolant in closer contact with the components.

The cooling mods were not necessarily to lower ECT, and actually, theoretically could increase average ECT by reducing the ocurrence of localized hot spots. In other words, stabilizing the temps inside the block/heads, particularly the rear cylinders and the valve seat areas.


Now that we have better flow and heat absorption, we need to get ruid of it thru the radiator.


I've heard numerous arguments that "my truck doesn't get worked hard" etc reasoning the lack of need for tehse mods, yet many of these trucks end up with nasty cracks between the valves. My 1996 (high capacity cooling from new) had 118k when it popped and had been run hot many, many times in it's life. There was not a crack to be found except in the precups. I think if you look at head cracks from 1997 up you'll find a great reduction in frequency.

YMMV....

[ 01-04-2006, 06:42 AM: Message edited by: kennedy ]

[moondoggie]

Good Day!

I hope we can get these great topics back to fixing trucks & not each other. It's really pretty easy - talk about our trucks, NOT the folks driving them & asking the questions. ;) It's always amazed me - our most knowledgeable folks are the ones that can't deal with someone else having a different/bad idea. On those RARE occasions when I am absolutely sure I know something, I try to remember to laugh only to myself at the other moron's stuff. That way, when I find out I was wrong, I'm the only one who heard me laughing - lots less embarrassing.

Come on, folks, I know it would cost you almost nothing if you got really irritated & left us, but it would cost me dear: I CAN'T EXIST WITHOUT YOUR HELP! :( Let's keep the heat in the cooling system & out of the dialog.

Thanks & Blessings! :D

[JohnC]

Don't forget that the net pressure due to flow nets out to zero through the whole system. Any increase in pressure is due to flow restrictions and is coupled with a decresase in pressure somewhere else in the system. Thus, unless the high pressure point was the recovery tank, which it isn't, you wouldn't expect any problems with the pressure cap.

[nvmtnlion]

I rarely tow, only twice anything of any real weight. But, I can say that I wouldn't want to drive here in Northern Nevada without the 1997 cooling upgrade kit. I did for one summer, and empty going over some of the passes, I would get close to overheating. I ran with just the updated crossover for a while but then installed the pump too. Right before the weather got cold, I hauled a friends tractor without any overheating.