Overheating after cooling upgrades

[dieseldummy]

A little background info. About a year ago I had to overhaul my engine. While it was out I had the radiator roded out and cleaned, installed a HO water pump, and modified the stock fan clutch to engage at lower temperature. After all this pulling through a lot of hills it would still get up to 240-250 degrees. Next I added a duramax fan and a modified new '98 model fan clutch. It helped a little more, but still no dice. I finally got the dual thermostats installed w/180 robershaws in it. Today I was hauling some hay, probably grossing close to 30K, ambient temp was near 100 with quite a bit of humidity. I was cruising along marveled by the power I had at my command, commenting to myself that 22lbs of boost and EGT of never more than 1100 was awsome, when I looked at the coolant temp and it said 240. Instantly I was back to the ****ed off 6.5 owner I was when it was stock. Everyone that does these mods seems to report complete success, why isn't it working for me. The only thing different about my rig is that I have an intercooler mounted up front, but I would like to think that isn't the sole problem here :( Any of you had similar experiences or any ideas of where to start for me??
Thanks,
Justin

[GMC Hauler]

Hate to ask the obvious question, but could the gage be wrong?

[jspringator]

Yeah, DD, but look at the weight you are towing. I tow 9,000 lbs, which is more than the tow rating, and my temp gage hovers between two clicks over 210, and two clicks under. I am very happy with my temps, although I need to add some water wetter and clean my radiator just in case I run into some extreme situations. Everything is relative.

[markrinker]

I wonder what the temp of your piston crowns was at that point...

[dieseldummy]

GMC Hauler, Yeah I'm sure the gauge is pretty much right on.

James, I agree with you about the big load thing. It's just so frustrating that if I run a Dodge or Ford with the same load it isn't even an issue.

Mark, Why would the piston crown be hot at this point? Only a max of 1100 egt and mostly 950 sustained.

[RT]

You are grossing about 30K and wonder why you are running hot??? Whats that, about double the factory tow rating? How about a larger radiator? They put a custom 5row core in the Power Project truck. Maybe thats the next step. RT

[john8662]

DD,

You did mention the 98+ style fan clutch and Dmax fan, but is this the stock 98 clutch? If so, throw it away! Call Kennedy up and get his custom fan clutch that kicks in at 180 water temperature. I can't brag enough about how much this one clutch made on my cooling problems. The dual thermostat mod gets better flow through the block, but it WON'T run any cooler.

I only noticed that I got my engine hot when pulling when I couldn't hear the clutch ingage. When I would slow down, and accelerate again, the clutch would kick in and things would just start to cool back down again. The problem lies in getting it up to high temperatures, if you can keep it from getting to higher temperatures (ex. 210 or 220) then you have less to cool down. Thats why I like the lower calibrated fan clutch that Kenndy has.

I was running the KD clutch and the metal fan not the plastic dmax fan. Wish I had done it sooner, before I cooked the orig engine.

[rjschoolcraft]

The KD clutch will make a difference.

However, I think the intercooler in front of the radiator is part of your problem. The 6.5 cooling system is just OK when modified. The extra heat load from your intercooler could drive it over the top again. Do you have the dual thermostat cross over?

[dieseldummy]

John, It is a '98 clutch, but has a couple of my own proprietary tweeks :eek: . It will kick in about 185-190 at any rpm and hold until things cool back down. It was on mostly all day usually just running the A/C causes it to come on for a while if that tells ya anyting. I would have loved to buy Kennedy's clutch, but it was either that w/a fan or the fan, dual stats, and this clutch for the same price roughly. I feel confident that the clutch and fan are not the problem here. It will literally try and suck my shirt through it when it is engaged and the engine is reved up.

I was hoping someone might know how much heat the IC will add to the mix. I know it isn't as much as the A/C just from observations I've made, but still wonder how much?

The fact that I'm grossing such a big number really isn't the big factor here either. I know of a number of 6.5's that in stock form run hotter EGT's while pulling little loads than mine does pulling big ones. In my experience EGT and ECT are directly related. If EGT goes up then so does ECT. Like I stated previously my EGT never went over 1100 and 950 sustained. In the past I have run 1250 or so sustained and peaked at 1400, if that were still the case I could see where part of the problem lies.

RJ, Big 10-4 on the stat housing. It isn't modified like most setups are for mechanical pumps either. It is just like it was origionally made.

[eracers999]

DD:

Take that rodded radiator out and throw it away. Cant tell you how many times that rodding did not work.

Kent

[twaddle]

Hi DD,
I'd get the radiator recored with extra tubes, The top and bottom tanks have enough area to take extra tubes.
Or get a custom alloy radiator made up with extra capacity.

Which area of the radiator does the Intercooler sit in front of?
If it is too low the coolant at the lower part of the radiator may not be getting cool enough.
The other thing was that the ambient temp was around 100 which isn't helping.

Good luck

Jim Twaddle
Biggar, Scotland

[markrinker]

Mark, Why would the piston crown be hot at this point? Only a max of 1100 egt and mostly 950 sustained.


I am not an engineer, but it seems likely to me that if you are seeing higher than normal water temps under load, you would also be experiencing higher than normal cylinder head temps, and thus the question about piston crown temps.

I have a theory (unproven) that EGTs can appear artifically low when running high boost (high air volume through the engine) when in fact you still have heads/pistons/valves suffering from too high pressures - which correlates directly to higher temperatures. There has to be a dimishing point of return, and the heat is still there, just not being accurately measured, due to the volume of air passing through the engine.

I have seen this same low EGT / high water temp relationship while experimenting with boost settings >15lbs and loads >10K on truck #2. It is always accompanied by a marked rise in water temps, even though my cooling system is in good working order, with JK clutch, clean radiator, and dual t-stats.

You can add a larger fan and larger radiator, and get water temps back into a range that will make you FEEL good, but the same problem will still exist inside the cylinders, in my opinion.
Your heads, rings, and piston crowns can still be too hot. They are simply outpacing the factory water jacket ability to carry the heat away, regardless of radiator volume and efficiency.

However, these are my theories only. I have no hard science to prove it. I do know you can weld (melt metal) underwater, and burn a flare in a windtunnel. Neither the body of water, nor the air exiting the wind tunnel will have a measurable increase in temperatures.

[ 06-20-2005, 06:01 AM: Message edited by: Mark Rinker ]

[rjschoolcraft]

"Another consideration that makes supercharging of Diesel engines attractive is that, for a given power output, it is possible to use lower fuel-air ratios as the engine's inlet density is increased. When starting with an engine designed for unsupercharged operation, it is often found that an increase in power and an improvement in reliability and durability can be obtained by supercharging. This comes about when the increase in air flow achieved by supercharging is accompanied by a somewhat smaller increase in fuel flow, which leads to lower combustion, expansion, and exhaust temperatures and to reduced smoke and deposits."

Charles F. Taylor, The Internal Combustion Engine in Theory and Practice Volume 1: Thermodynamics, Fluid Flow, Performance, 2nd ed., rev. (Cambridge: MIT Press, 1985) 463.

The lower exhaust temperature readings associated with higher boost pressures are real. Your observation of higher coolant temperature may be explained by the fact that losses (friction, pumping, etc.) increase with increased power output.

However, my engine coolant temperatures ran significantly lower through the summer of 2004 than they did in the previous summers. The power output of my engine in 2004 was significantly higher than in previous summers as well.

[markrinker]

...and then the pistons melted, right?

[rjschoolcraft]

Yeah, that's right.

I know what caused this to happen, but you can make up your own mind. Just be careful not to draw conclusions based on incomplete data or incomplete understanding. :cool:

[mhagie]

Back to the intercooler up front, the original Project truck has it mounted at a slight angle in front of the radiator support so heat from it won't directly affect temp passing through radiator.
That is if I remember correctly.
I would think that if one has a intercooler plus the oil cooler plus the a/c condenser all in front of the radiator and ambient is 100 degrees that is pushing the envelope to its max, if the radiator isn't absolutely 100% temps are going to go up in proportion to load.
Just my thoughts.
Merle

[JohnC]

Are you running an automatic? What speed were you pulling at? Was the torque converter locked? I've made direct comparisons between an automatic and a standard pulling the same load over the same route. The Standard NEVER broke a sweat whereas the automatic was pushing the limits often. Conclusion: The automatic adds a very significant load to the cooling system (even when the converter is locked). I never got anywhere near 30K, either...

[More Power]

What turbocharger are you running that generates 22 psi?

If it's a GM series 6.5 turbo, I suspect that's part of the problem. The turbine is too small for big numbers. Life is good at 18-20 psi with a Peninsular turbo.

Radiators... I'm now recommending people go with the 1994 or newer aluminum style with matching fan shroud if they need to upgrade/replace their copper/brass radiator. The aluminum rad cores are a couple of inches taller, which requires the new fan shroud and upper mounts. The shrouds/mounts are pretty cheap.

I've spoken to one member recently who upgraded his copper/brass radiator with a 5-row core. He had fitment issues with the core support, and didn't remember the minor mods I made to get it to fit properly. Another member couldn't locate a rad shop that could get the 5-row core.

So, I'm now recommending the 1994+ aluminum. It'll bolt right in with the new fan shroud and new upper radiator rubber mount brackets using the same bolt holes in the core support.

MP

[dieseldummy]

Kent, What is wrong with having a radiator overhauled? The guy I had do it did a good job I'm sure, although it didn't look like it had been apart since it was new...

Twaddle, The IC does sit in the middle of the lower half of the bottom part of the radiator. I never thought of that being a cause.

Mark, I would say there may be something to your theory. The only difference between the 6.5 and other "real" diesel engines I see is what true cylinder pressures are under 20 psi boost at 21:1 VS 18:1 or lower. The 6.5 is the only one that really has cooling problems so Maybe all that pressure forces the heat into the pistons, head, cylinder, ect.

Mhagie, I have all that plus an ATF cooler. The AC was not on however for obvious reasons.

John C, It is infact an automatic. Torque convertor was locked on and off through out the trip. I still maintain the intake cooler for winter operation against my better judgement. I have a medium sized auxilery cooler too.

MP, The turbo is a Holset HY-35 and used to be a WH1C Holset. They both provide a similar amount of power, the HY-35 just spools up a little faster. According to dodgeram.org the Hy will choke at near 30 psi so I would say I still have some room in that area. I've been thinking about trying a 5 core unit, but don't have any idea where to begin. I have the reprints for the power project, but don't recall any part numbers or anything for the radiator??

Keep it coming guys, makes my mind a spinning.

[rjschoolcraft]

Pressure has nothing to do with heat transfer...

[dieseldummy]

RJ, Let me see if I understand this correctly, an example in my limited mental capacity redface.gif . If a hot flame is directed at a piece of metal with a theoretical pressure of 10 psi the effect on the piece of metal will be the same as if it were being presured up to 20 psi worth of force? The fact that the heat is being driven with twice the force at the iron means nothing? It wont heat up faster or burn a hole sooner? I guess I just don't see what your getting at here. I'm not saying the I agree completely with Mark's theory, but I beleive it does have some valid points. I'm just trying to have an open mind when it comes to stuff like this because the most unlikely stuff is sometimes the bigest factor to a lot of problems.

[rjschoolcraft]

You're thinking of a torch, being fed with pressurized oxygen, which makes the flame hotter, making the differential temperature larger, making the metal heat faster. The pressure of the surroundings has no effect on the heat transfer.

The fact that a thermocouple placed in the exhaust stream immediately down stream of the combustion chamber measures lower temperature with higher boost means just that...the temperature is lower. From this, we can deduce that the combustion temperature is also lower. The two are directly related. In the cylinder, high pressure fuel is being injected into a pressurized volume.

You can't "drive heat" into parts by increasing the pressure in a vessel.

[dieseldummy]

RJ, I see what your saying. The model of a torch I used is pretty much the opposite of our engines. A flame of a torch is fuel fed by air, the flame in our precups is fuel fed to air. Do I have it yet?? smile.gif

[eracers999]

DD:

The radiator you had rodded out needed to be rodded out because it had electrolisys, once this has happened it cannot transfer heat efficiantly. My money is on the new rad making a difference. Run a pint of DCA in the cooling system once a year and that new radiator will stay good.

Kent

[markrinker]

Originally posted by ronniejoe:
Pressure has nothing to do with heat transfer... Agreed. Pressure doesn't 'force' heat into parts. However, pressure creates more heat for the parts to absorb, and for the cooling system to keep up with. You can slow that absorbtion into parts with insulators like ceramic coated pistons. You can speed the release of that heat with higher flow cooling systems and lower coolant temperatures.

RJ - I have experienced the 6.5 EGT characteristic you support - i.e. EGTs falling off as boost pressure is increased, somewhere above 15psi.

How do you explain this characteristic, if not a function of excess air flow through the engine for a given amount of fuel? Doesn't this defy a basic principal of physics - i.e. cylinder temperature dropping as pressure is increased?

I am not trying to be argumentative here. I really want to get to the bottom of this.

[rjschoolcraft]

This gets into the chemistry of the combustion process...an area where I need to do some brush-up work before I can definitively answer your question.

[gmctd]

Increasing air-to-fuel ratio in the cylinder - increased Boost levels - lowers peak combustion temperatures, reducing various noxious emissions in the process.

However, if you surf on over to the Member's Area, Cylinder Head Repair article, you'll see the major 6.5 cooling problem area.

A cross-sectional view of the cylinder head reveals the major coolant-flow restriction - the indirect injection pre-combustion chamber - and why the 6.5 heads usually crack between the valves.

Which was why the larger '82 exhaust valve was reduced in diameter for the '83-up heads.

And why this engine is very difficult to cool under stock circumstances, much less at increased power levels.

The high-output water pump and dual t-stat system increased continuous recirculative flow thru the block and heads, and also increased flow thru the radiator, without decreasing recirculative flow thru the engine, as in the earlier system.

The late heads were reported, in magazines and factory blurbs, to be redesigned for increased coolant flow thru the pre-cup\valve area, probably to meet the additional requirements of the proposed 215hp upgrade, which never made it to the streets.

Whatever, however - check out the pic of the cross-sectioned head.
That tells the tale, far as I'm concerned.

IMO, of course.

[rjschoolcraft]

The convective heat transfer equation is q" = h*(Ts-Tf) where q" is the heat flux, h is the convective heat transfer coefficient, Ts is the temperature of the surface of the body and Tf is the fluid temperature.

h is influenced by many parameters (fluid velocity, composition, turbulence, etc.). Ts-Tf is the temperature differential, or motive force for heat transfer. For a particular engine, the difference in h between 10 psi boost and 15 psi boost is not much. Therefore, the temperature differential is the primary influence...regardless how much power an engine is making.

Now, what does vary with power output is the loss due to friction. This will increase heat load into the coolant system...on any engine.

DD's problem, in my opinion, is the fact that he has an intercooler in front of his radiator and is running 20+ psi boost. The IC is rejecting significant heat into the air stream that is expected to accept heat from the radiator. That is why I've stated before that I would not put an intercooler in front of the radiator on a 6.5 even though that is the normal, logical place to put it. The 6.5's cooling system is just not able to accept it.

[Tough Guy]

Oh Boy...

30K is 3.5 times the tow rating of the truck....
(regardless if a PSD or Cummins can do it.)

The Power Project 6.5L has 18:1 pistons with a GM-8 turbo along with all the other cooling stuff...It still runs 205-210 on hard pulls with 10K in tow. So....if you put another 20K in tow, it would run 240 degrees too.

The 6.5L engine can only flow "X" amount of air efficiently, regardless of turbo and exhaust size. With IDI there is more heat tranfered to the heads, block and the coolant.

If you pull loads like that regularly, you need a Ford PSD F-550 it has the tow rating you need. It has the brakes and gears you need. It has an engine that can produce the power you need.

I will say this, I am impressed as hell that your truck performs as well as it does.

Cheers

[gmctd]

I'm thinking the same thing, rj - gonna need a much larger fan to move much more air thru the semi-blocked radiator at those Boost levels.

IAT out of the compressor must easily be 300deg

Or, unblock the rad, as in most of the charge-air cooled 6.5's.

The DP Project Truck is a pretty fair example of how to do it, imo.

[moedog]

QUIT SPENDING ALL YOUR TIME AND MONEY ON A DIESEL THAT WAS A BAD DESIGN FOR HEAT AND NOTHING WILL GET YOU OVER THE DESIGN. 30000LBS SHOULD TAKE YOUR TRANNY,U-JOINTS AND DIFF.OUT AS WELL.
MAY I SUGGEST YOU BUY A BABY DIESEL OR EVEN A USED FULL SIZE DIESEL. I WOULDNT WANT TO STOP THAT KIND OF WEIGHT WITH A PICKUP. SHOULD MELT THE BRAKES REAL QUICK!!!!!!!!!!!!!!

[john8662]

moedog,

Caps LOCK buttom stuck huh? tongue.gif

DD,

I wonder which fan is really more efficient at moving air, the bigger steel blade fan or the Dmax fan when used in our application. I vote steel.

[dieseldummy]

I guess I just expect too much out of what this thing is. It was just the fact that after reading all the sucess stories about the cooling upgrades and then having a failure I got all riled up before thinking through the facts. I only tow loads like this a few times a year usually hauling hay, so I think a bigger rig is a little impracticle. I use common sense when driving, treat it like I'm in a petercar and have no problems stoping or manuvering. (if emergancy braking is required the trailer brakes have enough power to put my face into the steering wheel...) Surprisingly power isn't an issue at this point it will go faster than I want to drive with a load like this...

John, I would really like to know that too. IIRC Kennedy favors the steel fan does he not?

I see what every one is saying about the weight being a factor, but I am still hung up on the fact that if EGT is low then the ECT really should be too. If I had more time to experiment I would do back to back temp recordings of air temp through of and around the radiator area with IC and without. That is probably a big factor to I guess.

The last load I pulled today grossed 28,xxx. I did a little experimenting with throttle postition since I had come up with a theory as to part of the problem. It seems if I let of the peddle a little the power is still there, but the high ECT isn't as great, never broke over 220 with this approach. I think this is where timing advance comes into play. As the throttle is pushed in a rod on the side of the pump pushes the advance piston which retards timing, or so I'm told by those in the "know". I have been playing with my IP trying to get more fuel out of it at higher rpm's so in the process I got more throttle movement out of it, but no more fuel. This means that the rod will now push the advance piston in farther than normal resulting in retarded timing at full throttle. This would usually show up in the form of high EGT's, but I don't think it does in this case since my turbo pushes more air than the engine needs and the cam from the Diesel Depot is seemingly designed to have more valve overlap for a better scavenging effect of the exhaust gasses. In essence the cool boost pressure is pushing out/mixing with what would normally be unburned fuel/hot gasses so the pyrometer can't accuratly show what is going on in the cylinder. Does any of this make sense at all?? It's late and I can't think quite well enough to type this like I am trying to so bear with me here... ;)

BTW, thanks for the kind words moedog, I'll be sure to take that to heart... :(

[mhagie]

Another factor that could help is gear selection,mainly pull the nasty hills in the highest gear that does not load the engine to the max.
If you can maintain any reasonable speed using only 3/4 throttle then everthing works better.
Less load,less heat,as your last post indicates you are on to.
Common sense applies here you could pull 40k and get by as long as you are aware of your enviroment and act accordingly.
It would be nice of course to have a bigger truck that you could impress your neighbors with but at 60 to 80k the incentive to impress deminishes severly.
Merle

[BuffaloGuy]

Howdy. I've been hauling hay too and have been grossing about 30K. My rig pulls it pretty good up to about 50 mph then the wind eats up all the power and that's it in the speed department.

I do not have an intercooler but I do have water injection. Without some form of intake cooling the truck is worthless pulling big loads.

Water injection doesn't move the heat to the front of the radiator but effectively eliminates it. It has its obvious down sides too.

After reading your posts it sounds to me like you might have a couple of problems.

First, I think you are pushing too much boost and too much fuel. What we are doing with these trucks is way different than what most of the fellows on this board do. I had almost the same problem when I ran my boost up to 14 lbs sustained with my little stock turbo. Yes, my EGT's were fine but my h2o temps were a problem. Just like you. Other guys may be able to run that high of boost fine but I'll bet they aren't pulling 30K either.

Even the 1/4 mile racers don't even compare as their load is for a short burst. We have to put sustained power out and deal with the sustained heat that that creates. All that heavy load creates alot of added friction and therefore heat.

The other place that I would look is at your tranny. I have a manual and pulling loads like these at highway speeds it can get pretty hot. I can't imagine how much heat an auto would be dumping in front of the motor. It must be a ton!

Now with all that said - My next motor will be a Cummins. I'll probably have to buy a Dodge to get the motor. These 6.5's are just too light to do this type of work (even just occasionally). In the meantime, I will be nursing this motor along with the big loads.

Most guys are pulling 9 or maybe 10,000 lbs and can get these motors to do just fine. Heck, my trailer unloaded weighs 5000 lbs and I'll bet yours is about the same. On a farm or a ranch there is just no way to keep all your loads under 10,000 lbs and still make it pay.

Good luck!
Ken

[dieseldummy]

Ken, It's good to hear there are other members on the board that do the same as me. From your sig it seems as if we have very similar pickups too.

I've got a buddy with a '96 that has water injection and when it works it keeps everything cool, when it doesn't everything goes to hell real quick. Is yours similar?

The problem arises for me when I climb bigger hills or get in a lot of stop and go type driving. Cruising 50 isn't much of a problem so it stays cool on the flat straight aways...

I agree on my next being a cummins. Although around here used duramaxes are similarly priced... Maybe once I get some time, like maybe this winter I'll get some stuff moved around and try again.

[eracers999]

DD:

With all due respect to everybody i dont and wont buy the 30k is whats makin it hot gig. Been there and done that with 27k from Dallas to MPLS many a time.

1. Are you hearing the clutch fan roar yes or no? At what temp if you are? If you arent hearing it roar thats a problem.

2. I think i follow your previous post on pump timing. If you are a couple degrees too far advanced on pump timing you will heat up quick. Its well proven on big diesels that the more fuel, boost is givin the more the timing falls back. Your non electronic, so static timing is super important, if your rattling under full power your hurtin it. Diesel timing compared to gas is way different. Set the gas theory aside and relearn. Dont know what you do know so no intent to offend.

Sometimes it may be neccesary to back out of it a bit and let it up. All riggs have to get out of it sometimes.
Your positive that the radiator is 100%??

Kent

[dieseldummy]

Kent,

Yes the fan clutch roars. Been cutting in at around 195 or so. I'm glad the timing thing makes sense to someone else. I was going to play with it some yesterday, but now that I have the wonderful dual stat housing it is in the way to do the 1.5 minute timing bump. The only person I know around here with a timing meter for these is not exactly someone I trust to do what I want. He has his own ways of thinking. I'll tell ya all I know about gasses: Forget them and run diesel. I can change parts and follow directions of what to do with them, but have never really cared to know details about the whys and how to's...

I've been backing out of it since I first had the problem on sunday. It just makes climbing hills a pain sometimes... I can't say for sure if the radiator is 100% because I didn't whatch him do it, but I do have a lot of respect of my radiator guys knowledge and intent to do things right.

[Kidd]

Sometimes you have to back off on the throttle in order to keep things cool. I haul up to 41k gross at times, and I won't go over 2200 rpm.
The fan clutch doesn't even kick in, and everything stays cool. Yes, long hills take a while. However, at work I used to haul loads up to 200 tons with a 500 hp Cat under the hood.. and I was down to 5 mph on some hills. So 30 mph with my dually is not bad. :D :D
K.D.

btw, my 98 dually is still bone stock.