New HO waterpump without dual therms upgrade..

[rameye]

I have the front of the engine part..trying to get it and running up for this week. Running outta dough and patience.

Found a new HO waterpump for 20 or 30 bucks more than the standard pump...thinking I might go this way. I'm sure I wont get the benefit of the full upgrade but its gotta be better than the original pump....right?

Your thoughts..

[Robyn]

Cant hurt at all.

[ronniejoe]

Do a search on this subject. There has been much discussion about it. I posted some pictures once that show there is a significant increase in flow area both through the thermostats and through the bypass with the new housing. GM reported popping freeze plugs when running the new pump with the old crossover. There's been lot's of argument both ways.

[Mark Rinker]

I ran an HO pump with a single thermostat system in a 1994 K3500. We later removed the thermostat completely and it ran much cooler all summer, and still made good heat in the winter while plowing.

[Chicago TDP]

I think the radiator cap will burst before a freeze plug, right? Is' that suppose to be the first place of pressure release?

And the HO pump is just a larger dia impeller I think, which helps the flow more then increase pressure, the better the flow, the less pressure you have, they are an inverse of eachother. I am almost certain too that it is a 37 gpm pump instead of a high 20's gpm.

I also know there is a second revision offered. When I purchased my new 05 Pen motor, I came with an extra water pump that was a little beefier then my 1998 hi-flo pump. I put then on the truck and it seems to always stay cool, I have pulled 12k and had no overheating issues at all.

[Kennedy]

I've seen confirmed reports of block heaters vacating the block with this setup. I guess simply put it just makes sense to do it right the first time...

[john8662]

For a temp fix, you can install the HO pump w/o the dual stats.

The recommended practice is to complete the upgrade when you can.

I can't find THE thread, but here is a good one..

Why Are Dual Stats Part Of The Upgrade (http://www.thedieselpageforums.com/tdpforum/showthread.php?t=24588&highlight=cooling+mod)

[dieseldummy]

I'd still like to see all these blown freeze plugs and block heaters... I put over 15K miles on with the HO pump and single stat. No issues here. When I had the motor out the freeze plugs and heater were just fine. The dual stats will help cooling, but aren't exactly necesary.

[rameye]

Wow...I know a little about centrifugal pumps..(20 yrs in the FD) I never figured that little of an impeller change would build that much pressure!

I figure the pump would "slip" instead of build great amount of pressure as opposed to a positive displacement pump.

I agree with JK that its best to do it right, but I'm at the bottom of the money barrel right now. Couple that with the fact that this engine @ 157K probably has a less than a 40K life expectancy before it grenades.

Just afraid to dump more money into it...would rather pay it forward towards a new power plant.

As always your comments are much appreciated..

[oilburnertoo]

I installed a take off HO water pump on a '91 6.2L PU [was off a crate motor & not aware at the time it was an HO pump] the issues I had were the side tank blew off at the seam twice on a brand new Harrison OEM radiator. After the second time I looked a little closer at the pump and saw the "HO" on the casting. I replaced the radiator again with one for a '94 6.5L aluminum w/plastic tanks and no problems since, BUT looking back I would put the whole package on at the same time and be done with it. The money I spent on the radiators alone would have paid the labor to install the pump and dual T-Stat manifold the first time around. Coincidence, I don't know?

[More Power]

Way back in 1997, I had an email conversation with a GM cooling system engineer about the then new 1997 cooling upgrades. He told me that one or more test engines loosened/blew softplugs as a result of using the 130-gpm water pump without dual t-stats - under some unspecified operating conditions. That is the primary reason for the dual t-stats.

Now, I have also heard that many 130-gpm water pumps have been sold as an upgrade item to lots of 6.5 folks who didn't also install the dual t-stats. Did any of them experience a problem? Maybe. Maybe not. I don't know.

If someone wants to run an HO pump w/o twin stats, I'd say go for it. I wouldn't run a 130-gpm pump without dual stats, but you can let us know how it turns out for you. :)

Jim

[rameye]

Well I guess I can be a test case...in the Mean time I'll cruise the junk yards for the dual stat setup....gotta be a few out there...

regards

Tom

[Kennedy]

If I were to run the HO pump w/o the rest of the upgrade I might be inclined to eliminate the bypass block off part of the OE single stat or try the older 6.2 stat w/o this feature. This should give the coolant somewhere else to go...

[rameye]

JK can you elaborate on that?? Whats the difference for the lay person??

[ronniejoe]

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

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

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

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

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

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

DmaxMaverick, why did these show up as links instead of as embedded images?

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

[DmaxMaverick]

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

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

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

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

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

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

DmaxMaverick, why did these show up as links instead of as embedded images?

Not sure. I'll reply to your PM.

[Kennedy]

JK can you elaborate on that?? Whats the difference for the lay person??


When the single stat with the bypass blocker (92-95 I believe) it blocks off the bypass hose so the only place flow can go is through the stat and radiator as well as the heater core. The dual stat config has no block off so there is a lot of area for the coolant to flow through.

I've recently heard of a Dmax that has been pushing out plugs after overhaul so yes it can be done...

[daustin]

Well I guess I can be a test case...in the Mean time I'll cruise the junk yards for the dual stat setup....gotta be a few out there...

regards

Tom
I know a friend that got a new dual thermo crossover from NAPA for about $80. I'd go that route unless there's a deal ot be found in the boneyard. The 6.5 is rare in the yards around here.
Don

[rameye]

Hmmm Napa ...only 80 bucks sign me up!

Thanks for the insight...coming up empty in junk so far.

tom

[daustin]

I looked for several months at the boneyards, not one to be found around here. I figured it would be pretty easy to find a used dual thermo housing BUT NOOOO.. LOL I was griping about it to a friend who has a 6.5, and he told me about the NAPA deal. The $80 was for the main housing, didn't include the thermo's, outlet ...etc but it sill sounded good to me. Next payday i think i'll see if i can get one at my local NAPA.
Don

[john8662]

JK's idea above is how I figured those that were not having problems were getting by with the upgrade.

I don't think it'll hurt, afterall the new 2-stat one has no bypass block-off.

J

[Shikaroka]

If anyone can get the part number for NAPA, please post it or send it my way.
My local guys can't find it.

[dieseldummy]

I've been running with the OEM single stat w/bypass blocker this whole time... I'm not saying it can't happen, but blown out freeze plugs and heaters are really stretching the worst case scenerio thing. I'm still waiting for the proof...

[rameye]

dieseldummy...

how long have you had this set-up????...

BTW I totally chickened out and pulled the thermostat...I will reinstall without the bypass blocker...

After working on this thing on and off for months on end...I started to freak when I thought about what it would take to pull the heads to get to a rear freeze out...

With advice from JK and pics from RJ and seeing the new set-up I've pretty much made up my mind that with the bypass blocked I am tempting fate..

sign me

Big Chicken

[GSE2SCHMIDT]

OK I gotta throw out the BS flag on the loosening freeze plug thing.

Let's say one morning it's 40 degrees outside. You start up your truck and get on the freeway before the thermostats open.....

....so lets see there are 2 thermostats, but they are closed

....somehow having 1 thermostat closed builds more pressure?

....so everyone with 2 thermostats, they must never close, and the radiatior can never have more than 9% restriction or POW no more freeze plugs

Also if the dual stat flows no more than 9% to the radiator, the dual stat setup would not have an effect until the single stat ran out of range at 100 percent open which would be 91% open for the dual....

...so how often is everyone running at or above 91% cooling?

....9% more flow to the radiatior wouldn't a single flow stat have better block flow?....flow has to go somewhere?

[rameye]

I'm guessing what JK and RJ were demonstrating that (as far as I can tell) is that with the single stat setup, with an OEM thermostat that has the blocker, is that when the thermostat is closed it will build pressure. Apparently with the significantly larger size impeller in the HO pump, it builds quite a bit more pressure than the small impeller. With the dual set-up, the bypass never gets blocked so it dumps pressure via the heater circuit.

What JK was offering as a compromise, was to remove the bypass blocker off the OEM thermostat, to allow any pressure to dump into the heating circuit in the same way the the dual set-up does.

Truth is the blown out freeze outs might never happen (Diesel Dummy is running that setup)...however my luck sucks, and I'm not in the mood to tempt fate to prove a point. JIm has pointed out that GM engineering has verified that the HO pump/single stat in the stock setup may cause a freeze out/blow out situation. This time of year this truck is the vacation mobile, and she needs to be up, running and stout..not leaking antifreeze on the side of the highway.

My $.02

[dieseldummy]

I've ran w/single stat and HO pump for 15K miles w/no problems. The last 10K was with dual stats and HO pump, also no problems. That was all on the origional motor w/148K ish miles. For the last 5K I've wen't back to the single stat/HO pump combo and still have no problems. I run a stock stat w/blockoff intact.

The only advantage I see to the dual stats is slightly better cooling ability.

[ronniejoe]

OK I gotta throw out the BS flag on the loosening freeze plug thing.

Your BS flag needs to be recalibrated...

[dieseldummy]

Lets recalibrate it with some proof then...

[rameye]

I guess we could screw a pressure test gage into the block where the sender unit goes and check it out...single stat, dual stat, single without blocker..

anybody game??

[robscarab]

Anyone get that part # from NAPA for the dual T-Stat deal? I called and they told me that they have never stocked anything like that. It took him about 4 seconds of "research" to respond, so I asked him if anyone else had asked for this piece? He said..no...Alrighty then, I think I will call back when the afternoon shift comes on. Perhaps I will get someone whom will at least try and look it up.... By the way, I said my truck was a 98 to avoid a lecture about how it wouldnt fit on my 93,but we never got that far... I hope I can just call back with a part number later, unless he's right ?

Also there are thousands of 6.5TD's in my part of Canada so I'll check the boneyards and let everyone know if there are some around town.

Rob

[rameye]

That would be great!!

$250 for a new one!!! :(

[gherrell]

That would be great!!

$250 for a new one!!! :(

Don't have the NAPA number, but Rock Auto (.com) has the AC Delco parts for the dual thermostat crossover:

AC Delco #1580782; Engine coolant thermostat housing (lower part of crossover): $104.79

AC Delco #151753; Water Outlet: $51.79

Get these parts and (2) AC Delco #131103; thermostats ($17.83ea) and you are set!!!

Regards,

Gary

[rameye]

Thank you for those numbers...I checked them out..those are Good numbers!!

much appreciated

[GSE2SCHMIDT]

Well the BS flag thing.....

My 1999 chassis engine(non-turbo) has the screw on fan style waterpump, all the part cross over lists show there is only 1 part number for many applications including the single thermostat that my engine came with. The pressure of the pump is basically going to be determined by how tall the impeller is and how fast it spins.

If the pump outlet is fully blocked the pressure will only increase so far and the power it takes to spin the pump will decrease. Pumps mostly use horsepower to pump the liquid, not pressurize it so much.

So lets say that a small impeller pump is good for 10psi and a large capacity pump is good for 15psi.

At upper RPM the pump will pressurise to max pressure from the inlet to the outlet. The inlet is coming from the radiator and that does not change.

The other end is to the radiator. So if the thermostat(s) is/are closed. Pressure will increase to 10/15psi repectively. Does not really matter if the bypass valve is installed because it is wide open pressure will increase to the whole block in seconds with or without restriction and it will sit there recirculating the coolant at the engine at 10/15psi at whatever gpm can flow thru the block. At this time if the freeze plugs are going to blow they will now.

As the engine warms up the thermostat opens and bypass closes but even with a totally open single thermostat and totally blocked bypass the block pressure will not increase and will actually decrease if the radiator cannot flow quick enough.

I think your right someone might have to do the pressure gauge test and yes the bigger pump will have more pressure, but with a totally closed thermostat(s) pressure has no where to go

[joescj5]

Great stuff here guys. I'm also looking at the best bang for my buck to help my chevy tow better. Reading through this thread I have come to believe if I were to install just the HO pump would run the risk of blowing out freeze plugs.

Now what would happen if I were to instal the HO pump, and then drill a modest bypass hole in the single thermostat? The engine would take a bit longer to warm up, but the T-stat should still function mainly normally. Now in my mind this should decrease the pressure through the block before the T-stat opens, and reduce the chance of popping freeze plugs. This should also allow a bit more coolant to flow through the block without resulting in cavitation.

I apologise if the bypass hole idea has already been discussed, but I thought it was a good fit in this thread. If anybody's done this then post up, let us know how it works. I've halfway convinced myself to pick up a new HO pump, drill a small hole in my T-stat and see what happens :D Somebody needs to stop me soon if this is a really bad idea:cool:

[tommac95]

>157K probably has a less than a 40K life expectancy before it grenades.
Possible , but I'm expecting 300K . Headgaskets may be in order , though....

The block freezeout plugs won't go anywhere [i removed a couple], the heater , maybe so.

Glad you raised the issue !

[j_k_auto]

I guess the single 180 stat,marine pump,cooler clutch with the dmax fan must be the ticket on keeping it cool. As We now when he comes out with a setup it must be great.

[j_k_auto]

Also I think if you would run a single stat an remove the bypass it would take care of the pressure build. that is my opinion.

[joescj5]

Well I just did it. Drilled four 7/64th holes in the flange of my stock thermostat, and installed a HO water pump. Just took it for a spin around the block and up a small grade. Put it into drive and kicked the RPM to just under 3k and cruised up the grade for about 2-3 miles. Temp made it up to 190, but I ran out of grade. As soon as I slowed down the temp dropped to 170.

Tommorrow, or later today actually :p My wife and I are going for a Sunday drive to look at some land. This will give me a chance to try out our local 6% grade for 7 miles right after the first 6% and 4 miles section of highway nearby:D

[j_k_auto]

Well I just did it. Drilled four 7/64th holes in the flange of my stock thermostat

Where did you drill the holes and why did you decide on that hole size?:confused:

[joescj5]

Where did you drill the holes and why did you decide on that hole size?:confused:


I drilled the holes on the mounting flange right up against the swell of the T-stat. The holes are evenly spaced around the perimeter. I went with 7/64th as they were almost the largest size I could actually use. There is just not a lot space around the perimeter of the T-stat. Basically there is very limited flat space that you can drill into, but I think there will be plenty of flow to prevent the block heater from being popped out by the new pump.

I only went with four holes because I still want some functionality out of the T-stat. I can always add more holes to increase flow, but the main point of them is to decrease block pressure before the T-stat opens. I was going to take pics, but by the time I got to that stage it was almost midnight, and I was kinda tired. We'll see how it does in an hour or so.

[j_k_auto]

You might of found a way for the single stats to actually work without the pressure build up. I am thinking on going either way at this point. I am tring to decide what is going to work best impo. I do have my crossover out and apart on my bench. I keep looking at it and thinking what would work best.
I am just tring to look at the flow pattern and tring to figure out why there will be extra pressure. I searched this for 6 months and now I can see first hand the difference detween the single and duel setup then maybe I can figure out what will be the right thing to do with the h o pump.

[joescj5]

We'll I don't know if this was the right way to do this or not yet, but it seems to be working pretty well right now. @75mph and normal freeway driving the temp gauge reads 185-190 deg. I started at the bottom of Horshoe Bend hill (6% grade, 7 miles) at 65mph. About halfway up the temp was at about 195-200 deg. I then romped on the accelerator and at the top of the hill the temp was 200-205 deg at 70mph.

This is easily 15 deg cooler than the last trip up the hill. In fact last trip up the temp hit about 220, the SES light came on and I lost all power (Set DTC 78 - Turbo Wastegate Solenoid Fault). Max speed was then 45mph until I crested the hill and the engine cooled.

Ambient temp this trip was about 65 deg, no load other than three adults, a 30lb rat dog, and 60lb Husky. So far this is a vast improvement. I'll post up if any problems rear up.

[j_k_auto]

joescj5 why don't your pm's work? I was wondering where you are located?

thanks joe

[rameye]

I'm running HO pump on single stat... I removed the bypass blocker off the thermostat..

Results so far indicate...

Definite inprovement, however I wouldnt run out and change my rig for the improvement i got unless I really needed some lower temps badly.

The real noticeable improvement was when I had the bypass blocker on the thermostat...the gage would barely move as I climbed hills, of course I wimped out with visions of pulling the motor to slam in a new freeze out plug and removed the blocker.

I like the holes in the thermostat idea...is that a factory stat??

[joescj5]

I assume it is the factory or a stock replacement stat. I've only had this thing for about a month, and it has had a lot of miles put on it by previous owners. So I can't be sure it is factory/stock.

I've updated my profile to include location, the lovely Boise, Idaho. I'm not sure why my PM's don't work, heck I can't even find where to access them:confused: I'll figure it out eventually. I am a little slow on the uptake, but I am still trainable:D

[DmaxMaverick]

.....I'm not sure why my PM's don't work, heck I can't even find where to access them:confused: I'll figure it out eventually. I am a little slow on the uptake, but I am still trainable:D

Cool. I'll train ya.

Go to your User CP (http://www.thedieselpageforums.com/tdpforum/usercp.php) (link at the top/left header area on every forum page) and enable the PM's. It's in the "Edit Options" link at the left of the User CP page. Go down to " Messaging & Notification", and check all 3 boxes in the "Private Messaging" area. Click "Save Changes" at the bottom of the page, and you're done. There are other settings available in the CP, so have a look around to see what is appealing to you. The PM's are off by default, which is necessary for reasons we don't care to discuss openly.

[GMC Hauler]

Look inside the dual thermostat crossover and the single crossover (early 96 model). There is a built in restrictor plate in the early 96 model. If you grind that plate away, and then go with the non blocker type thermostat, there is no difference in the recirc flow path at all. The thermostat will flow more water with this modified setup when open because of the increased pump head of the high flow pump. It will not flow as much to the radiator as the dual crossover. This setup is safe and will not pop freeze plugs because there is NO difference in the recirc path.

I've heard a few guys say that the thermostat will cycle open and shut rapidally because of the very cool water that was sitting in the radiator now rushing in the block (which is not necessarly good for the thermal stresses on the block). Drilling a small hole in the thermostat plate as a few of you have done keeps the radiator path somewhat warm and reduces thermal shock to the block. I've done this before (not this engine yet).

[Shikaroka]

How do you know if you are getting a HO pump?
If I go to the parts store and get one for a 99 Suburban, is it going to be a higher output version than my current one?

Like this one At Advance Auto Parts (http://www.partsamerica.com/ProductDetail.aspx?MfrCode=A1C&MfrPartNumber=D5511130&PartType=54&PTSet=A)

BTW:
What does "Pull-A-Head Design" mean?

[rameye]

HO pumps are conveniently stamped "HO" on the pump casting.

[More Power]

Here's an email I received from GM regarding retrofitting the dual t-stat and hi-cap water pump to earlier 6.5 diesels. I've not found the other email from the GM 6.5 cooling system engineer - yet, but the admonition was basically the same....

The following email came to me from Dan Fuller, who was a Northeast GM regional training instructor, and who was responsible for training dealer techs on the 6.5 systems in the mid to late 90's.



Date: Wed, 19 Aug 1998

Hi Jim,

If you use the GMT800 water pump on your 94, just make sure that you use the entire cooling system, crossover included. If not, the higher flow pump will create excess pressure in the system due to the restriction of the crossover. This also creates some tricky fabrication as the AC compressor and alternator were swapped to allow rear entry of the upper radiator hose. Let me know how you make out.

The purpose of the dual thermostat housing - more flow... Please caution readers about not removing the thermostat completely - I've had people try this already. The coolant flows through the engine with no restriction whatsoever and travels too quickly too absorb enough heat. Hence, the coolant is not all that hot but the engine metal overheats!

Dan Fuller

[j_k_auto]

Is there a number for him? I would love to talk to him about this and get some updated info.:)

[More Power]

His personal phone number that I have on file is over 9 years old. Do a google search. I found him in about 30 seconds. ;) I doubt there are too many Dan Fullers involved with GM service training..... It appears he still worked for GM as of December 2006 - and may yet.

Jim

BTW - the 1999 GMT-800 HO 6.5 water pump (treaded fan-clutch attachment) is not marked with the letters "HO". But, it does run the same size impeller as the 1997-98 GMT-400 6.5 HO pump - as measured by my dial caliper.

[j_k_auto]

Ok I found a way to contact him but I will have to call gm and do the run around till I reach him. I will have to wait till monday and go from there.
thanks for the imput on the pump.:)

[ttyR2]

My understanding is that thermostats also cause restriction that help build pressure in the heads, enabling the coolant to "scrub" localised boiling spots. I think I read such in an article by a tech from Stewart Components a number of years ago.

If that's the case, it's not just about flow, but creating pressure in the heads as well.

[tomtaylor]

If we are just trying to dump excess pressure created by the high output water pump from a closed circuit (that's before stat opens) then couldn't we just create a half inch circuit from the engine back to the rad with an inline pressure relief ball check valve rated for say 12-14psi or whatever the correct psi would be to prevent blowing plugs or gaskets or whatever else???

This allows only the minimum water through to correct the pressure problem would but still allow a better warm up cycle. Once pressure drop the circuit dies until it builds again and then once the stats open the circuit dies until the stat closes again. What would be the correct system pressure to prevent anything from blowing with stats closed? would it be 13-14-15 psi? Are people getting higher than this beofre frost plugs go? need to know where to set the pressure relief valve at?

The guy that was blowing his rad tanks maybe had a compression leak too? Seems odd that a pump would blow a several new rad tanks, but I guess anything could happen when dealling with so many variables.