HMMWV Overheat Q's and pictures

[86humv]

**********I did the TDM test and the fan spins up and everything gets noisy the second you disconnect the wires. So i'm guessing that's working well.
Also...make sure it kicks on when connected, just unplugging it shows the fan engages, but does it engage when its all hooked up and running hot ?
the gold valve gets clogged sometimes, not allowing the system to work properly.
I was driving one and it got to 240+ so I pulled over and unplugged the wire and she cooled of after fan engaged.

 

[vitamink]

The fan does engage when its all hooked up and running hot. It cools it down to 220 or so then shuts off. The needle goes back up, and just before 240, it kicks on and cools everything back down. It's like clockwork. For all intents and purposes it does seem to be working i just don't think it's working within the right range. The TMs say that i'm near normal, but it seems high. Others have stated that their Hmmwv's in non desert climates operate at lower temps.

 

[tim292stro]

If you hit the tank and thermostat housing with a laser thermometer and saw a >20* difference, I would not suspect the fan thermostat or engine thermostat is bad. Around 185*F is normal for internal combustion engines (diesel or gas). The boiling point of water in open air at about sea level (1 atmosphere) is 212*F (100*C) - with antifreeze it shifts a bit higher, and with the closed cooling system and a good radiator cap keeping the pressure in it rises a bit more too (without knowing what you radiator cap is regulated to, I can only guess your boiling point is about 220*F - so this is why the other commentor has said it is "not normal" he's right - it's dangerous for any water-cooled engine to be indicating a water temperature that high).

If you are seeing 240*F at any time, be assured that you should also be seeing a bunch of coolant flowing into the over-flow tank and eventually on the ground as that overfills - at 240, just about any water-cooled engine would be in full-on boil-over.

If you start with the engine cold, remove the radiator cap and then start the engine and let it get to temp - I'll bet your fan tuns on and then off without the radiator spewing coolant all over the place (which would mean it's not boiling anywhere in the cooling system). I that is the case, you can be assured that you can call BS on the gauge. Make sure that you take the radiator cap off when it is >>COLD<< if it was run hard at all and got to temperature before you remove the cap, you will lower the vapor point of the fluid and cause a spontaneous boil - which will eject sticky (glycol is a "sugar") boiling water all over your hand, face and chest (and anyone next to you). Think of it like being covered in boiling napalm... Treat it with the due respect!!!

I think either your wiring is bad, or you have a gauge+sender combination issue as another commentor has suggested. Be aware that your indication equipment can be messed up and the rest of the system can be running just fine. They are separate typically for this reason.

 

[vitamink]

I just swapped out the thermostat, just waiting for the RTV to dry and i'll see what's up.

 

[Lindsaym151]

Ok , Sorry I didn't sound off sooner.I raced for HUMMER for six years,You went through some mud and had a long straight a way after!What you did was fill the first coolant core with mudd. This F's everything up. Get a low pressure washer and soak your primary condenser coil with lotts of water.FLUSH it like six times!Your going to have two coils in front of your Radiator.Ok lets fix this,1st thing is call me @ 386 479 9644-I can run you thru this process in about 15 min. I paid my FAC mech 70 k a year , I know this fix works!

 

[vitamink]

I do wish mud was all it was. I should've mentioned that this hmmwv was built with all new parts and had only 150 miles on it. It hasn't been in the mud at all. I do appreciate all the information everyone has given as i'm sure at some point each of these scenarios may happen to me and it's nice to have other people's experience to fall back on.

Update on the thermostat...the problem still exists. I'm now thinking like Tim that it's a bad sensor or sensor/gauge combo...off to the internet to find where i can buy these sensors (any help on that would be appreciated).

I also just purchased a new hood grill (the more open looking one with the mesh) It looks like it can get more cool air circulating...i hope anyways.

 

[Retiredwarhorses]

Start with a temp gauge' I have had the read high before, also had an issue of bad wire with a high resistance short many moons ago....truck would read fine a Lowe temps, then when at full temp would peg the meter.
I had replaced the gauge and the sender with no changes....so I ran a wire from the sender direct to the gauge on the outside of the truck....problem solved....So I ran the wire permanent after that. Bad or loose grounds will cause issues too....unscrew the inst cluster and pull it back and check all the connections. Wiggle the connections when running....
you REALLY want to print out the wiring schematic for this truck from Kascars website....comes in real handy.
its also in the TM....also, speaking of TM's, you need to follow the troubleshooting section of the TM, as it has a running hot TS section....

 

[emmado22]

Make sure the gauge and sender are matched!!!! The 'cool guy' temp gauge with the LED doesnt work well with the 'normal guy' sender and vice versa.

 

[Lindsaym151]

Any chevy dealer or Cadillac dealer will have parts for that engine!

 

[o1951]

I never aimed the laser therm at the rubber outlet hose - maybe that is ok, maybe the rubber insulates a bit. Try the metal on the engine that the hose attaches to and see if the temp is the same.

 

[vitamink]

Lindsay, i'll stop there tomorrow!

Hummerguy, I'll check the wiring tomorrow thanks for the idea

o1951, as soon as it overheats, i'll take a reading

emmado22, when i get to the dealership i'll buy a matched set and plug them in...i'm sure i can use the extra parts.

 

[Retiredwarhorses]

Make sure the gauge and sender are matched!!!! The 'cool guy' temp gauge with the LED doesnt work well with the 'normal guy' sender and vice versa.

The older temp unit with the "cool guy" gauge I beleive reads cooler rather then hotter.
I have the "cool guy" gauges in my truck and use the standard TSU and all seems ok.
I have never removed one of the "gray bodied" TSU from any motor I have received from the military, yet Steve Owen from Owens export does have them.

 

[Retiredwarhorses]

Any chevy dealer or Cadillac dealer will have parts for that engine!

some.....and you will pay an arm for them at any dealership. Remember, all the sensors in this engine are 24v.
the mil 6.2 cdr setup is different then civ, glow plug types etc....I have never found anything at my dealership for anything I work on. Water pumps at o'reillys.....napa is your best source.

 

[actionpaintball]

For what it is worth, my 6.5TD reads and works EXACTLY the same. Fan comes on at 215/220 and tops off at 240 but never overheats. I did the same shake down as you, even ran some "water wetter"...still reads the same, but my infrared reader tells me its all about 200 and not 240...I keep an eye on it but have not changed anything.

 

[vitamink]

AP:

If i figure it out i'll send you a message on what i had to change to fix it or correct the issue. I too did the water wetter.


UPDATE:

I just got in my new hood radiator grill. I currently have the armored louver version and i hoped to switch to the more open mesh style. Unfortunately what i ordered didn't come with the mesh so i'm waiting on Kascar to send me some. I also ordered a NOS TDM to see if that works. I have a new gauge en route as well. As I said, if nothing fixes the issue, it'll be nice to have a spare.

While waiting on my parts, i made a license plate holder that i think works pretty well, if anyone needs pictures i can send them some.

 

[vitamink]

The TDM came in today but unfortunately it was fried. It smelled like burnt electronics from the time i pulled it out of the box. I drove around today with no TDM and the engine stayed at 219 the entire time which was nice. The fan being on constantly was about to make me deaf though.

 

[kdaniels]

Actionpaintball brings up a good point....i remember reading a while back about the 6.5 running hotter due to the thinner cylinder walls, basicly a bored out 6.2 block. If your engine was refurbed that might be something to inquire about. As others have stated 180-210 is the op-range mine runs in and you can feel and hear the clutch fan when it engages @210 and shuts off @ 190 in my truck.


SEMPER FI...

keith

 

[vitamink]

I put a new TDM in and it operates fine...the fan still kicks on at 230ish. I got a new gauge. I figure i'll swap that out next.

 

[Kane]

Any update on your issue? Did the new gauge correct the issue?

 

[vitamink]

I haven't had the chance to look at it as i was focused on a transmission leak and diff leak. The diff is fixed, not 100% that the trans is, but we'll see. I did take it for a test drive after fixing both. I also swapped my armored grill (anyone need an armored grill?) for the slat/mesh style thinking that maybe i had an obstruction or that the mesh would allow more air in...I was incorrect. It heats up just as quickly and shows 230ish when the fan kicks on. I did notice that if i tap on the gauge the needle jumps up a couple of millimeters so i'm assuming that's the culprit. I'll know more by the end of the week as i'm wiring in my comm system.