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Discussion Starter #1
I have noticed that most questions on this forum have to do with vehicles running cool. Not a problem here, believe me. The problem is the M1114 up-armored HMMWV with the 6.5. I know they have some added wieght to haul around but on a mild day here in the desert I watched the temp guage throughout a convoy and it rode between 230 and 240. It got to a point that I was about to demand we stop to let it cool down but luckily we made it to a stopping point so it had a chance to cool. Talking around this seems to be a common problem with them but I've never heard of any problems from people that have the 6.5 in their pickups. My dad has had several with no overheating problems. Is their a design flaw with the Hummer body that contributes or is it just the added weight combined with the fact that you can't keep the sand cleaned out of the radiator for more than ten minutes? Any info would be appreciated, especially from the Hummer guys.
 

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Excess heat can and will kill these engines. No cooling can be a bad radiator or flow through it be it air or water. A bad head gasket will also contribute, frequent over heating will cook the heads and now you might have a long walk.
 

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update your sig, 97 or 98 got the cooling upgrade.
 

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NWALLIS 1st welcome to the site, and Thanks for your service,

You might want to contact Heath Diesel www.heathdiesel.com Bill is head honcho there see if you can't get him, they have some fixes specifically for the military hummer one of them targets the overheat problem, initial tests with some Army units have been reported to be positve.

When I heard about the uparmor flak in media demanding armor be added; I wondered how long it would be before additional vehicle safety would be compromised by reliability.

Are you running turbo or N/A 6.5s.

The 6.5, heat and extra weight are not a good combination, 6.5 package even in our trucks can be a management issue to make power without overheating.

I abuse mine about as much as one can and get away with it towing up to 18K loaded trailer occasionally, but I added a retuned fan clutch, remote oil filtration that gives almost 2 extra qts of oil, an intercooler, extra trans cooler rated for 25K, and deep trans pan for extra 4qts trans. how much of this you can add to your Hummers and still be robust I don't really know.

You guys are extreeme offroad users, maybe the deep trans pan www.yourcovers.com , retuned fan clutch form Heath above or www.kennedydiesel.com , trans cooler http://www.derale.com/fanmountedoilcoolers.shtml
might be robust enough to help out

also maybe these guys can help you out as well with some ideas www.bluehummer.com
 

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update your sig, 97 or 98 got the cooling upgrade.
I'm not sure if this applies in a military hummer, don't know for sure IIRC all military ones have single thermostats so would be like pre 97 trucks I'm guessing
 

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TD's got a real good point... military stuff doesn't jive with our civilian model year improvements. They ran mechanical injection pumps longer before switching over to electronic IIRC.
 

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Discussion Starter #7
Thanks for the help guys. I appreciate it and will check out some of the guys that Turbine Doc suggested and see if we can't get these things coooled down and will continue to try to keep the radiators clean. Wouldn't be much fun to break down. We are running the turbos and the 6.5 is a huge improvement over the 6.2 believe me. We run single thermostats keeping with the army belief KISS keep it simple stupid. I just wish we could drop the DMax in.
 

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I'm a USN Chief no longer on active duty or drilling reservist; so I know bugaboos about non milspec stuff, but has anybody looked at water wetter for you guys? Maybe search the net for those guys that run Baha and other desert endurance races, mite be some good info from those guys.

Keep your heads down over there guys, you are in my prayers
 

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Or what about the purple ice from Royal Purple? Anybody have any experience with it? The only info I have is that it is compatible with green and orange coolant.
 

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Keep the radiator clean, Make sure fan is engaging,
lower gear,higher RPM keeps transmission cooler ( less heat build up in torque converter ) therefore less heat to radiator..
also more coolant circulating.
when you stop, neutral and 1000-1500 rpm to get temps back down.
 

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Running the engine at higher than 220*F will quickly overheat the rings and cause them to score TDC in each cylinder, increasing blowby and glazing cylinderwalls.

The best cooling upgrade I've done so far is the deep tranny pan. The extra fluid capacity keeps the trannies heat off the cooling system as they share the same radiator core.
 

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Agree on tranny pan, 30 degrees differance for me.
I doubt Old uncle sam will go for that fix though,

Torque converter makes most of the high transmission temperatures, High gear / low rpm pushing the torque
converter , really makes the temps increase ( pan/extra fluid makes a big differance )

Also , grade breaking with the transmission heats the fluid real quick,
 

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Discussion Starter #13
The best cooling upgrade I've done so far is the deep tranny pan. The extra fluid capacity keeps the trannies heat off the cooling system as they share the same radiator core.
Do you know how much lower the pan you're running hangs down than stock. I am not sure how much the army would allow but something has got to be done. I am not sure how many of these engines have died since my job this trip is not as a mechanic but I am sure it is only a matter of time if they haven't started giving up the ghost already. Hopefully some genius sitting in a big soft chair somewhere will decide that the clearance isn't as big an issue as the heat over here.
 

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The engine is in a doghouse, like the civvy vans - difficult to get sufficient flow-thru air to remove engine heat at low forward speeds, none at idle.

The turbo is mid-center direct-mounted, so little possibility of adding a charge-air cooler to keep the Intake Air Temperature below 200deg = high Exhaust Gas Temperatures = high Engine Coolant Temperatures.

Could be done, tho, similar to Ford and Duramax.

Would also help to increase coolant flow thru the block\heads with the HD hi-output water pump and\or the Hummer cooling upgrade.

Which will require much more air-flow thru the radiator.

Is that a hydraulic-motor driven fan or an electric-motor fan?

Either case, need to switch it to constant high-speed cooling, rather than variable by vehicle speed .

Hydraulic motor may require external power-steering type cooler to run full speed.

Could also reverse the flow when vehicle is stopped\idleing, which would serve to back-blow the sand out of the radiator.
 

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Look in FAQ pics for PML on mine, doesn't hang much lower than GM pan, 2 models out there 1 hangs a little lower than one I have, need to confirm with PML which one you need.
 

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Do you know how much lower the pan you're running hangs down than stock. I am not sure how much the army would allow but something has got to be done. I am not sure how many of these engines have died since my job this trip is not as a mechanic but I am sure it is only a matter of time if they haven't started giving up the ghost already. Hopefully some genius sitting in a big soft chair somewhere will decide that the clearance isn't as big an issue as the heat over here.
It is ~2 1/2" lower than the stock pan and much thicker, the one I have is PML ~5/8" cast aluminum for $200 USd.
 

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I wish I had something to add - the only times I've ever had to watch the heat were when I first bought it and was driving up the grapevine - I guess it just wasn't broken in enough, and when my overflow tank cracked and I started losing coolant.

I don't have the turbo or its heat buildup issues though. I would think you have the bolt on fan rather than electric. The problem there will be finding a 24v fan rather than 12v.

The hood scoop over the radiator stack might be worth a look if the overheating occurs while moving at speed.
 

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Trans pan will let you gain a little on overall temps,
But
Best immediate fix, KEEP sand out of radiator....
It packs in the corners of the fins, cuts the efficency of the cooling, Had mine clog up in dirt roads of Montanna,

About 6 hours of poking a thin piece of metal through
each radiator slot.. still ran hot on mountains , but
stayed within limits,
Note, can't blow out with air, to much pressure just folds over the fins and makes it worse,
Some use a cleaning solution and suck out the junk
with a shop vacum, but it does not get the grit completly
out of the fins...

Also , keep the oil&tran coolers clean, lower oil temps will
help lower coolant temps

I Do run 180 degree thermostats, full flow,
cheap ones do not open as far,
Wonder what no thermostats would do, ??????

Biggest problem, running a light duty diesel in a heavy duty enviroment......
 

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Can you pop your hood to give us an idea of air flow thru the rad and engine bay, YK?

Better yet, a picture(s), or two
 

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Can you pop your hood to give us an idea of air flow thru the rad and engine bay, YK?

Better yet, a picture(s), or two
Going out to work on truck shortly - will do some pix
 
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