How long should it take a humvee to warm up?

[Autonomy_Lost]

Well I thought I had a temperature sender problem, but now I think I have a thermostat problem.

Symptom: temp gauge never moves

Troubleshooting steps:
1. Connected sender input on gauge to ground. Needle goes full scale, indicating that the gauge is likely not bad.
2. Measured sender ohms to ground, 4.8k
3. Verified that sender has a good chassis ground connection
4. Verified that sender wire has continuity from sender to gauge.
5. Ran engine for 15 minutes, no movement on gauge.

I couldnt find an ohm spec for the temp sender, but mine was around 4.8k at 80 degrees. That seemed high so I replaced it. Then I took the following measurements while the engine was idling:


4.8k at 80 degrees
2.3k after idling for 10 minutes
1.3k after idling for 15 minutes
1.28k after iding for 20 minutes, needle barely moving

Is this expected behavior? 20 minutes seems like an awfully long time to have the engine still not reach temperature. Is my thermostat stuck open?

 

[Mogman]

CAMO will likely chime in with the numbers, he is the keeper of the numbers.
Does the thermostat housing feel hot? do you have a Chicom infrared temp gauge?
If your HMMWV is truly running too cold you have a one in a half million truck!
I suspect the sensor numbers are OK and the gauge is faulty

 

[Autonomy_Lost]

CAMO will likely chime in with the numbers, he is the keeper of the numbers.
Does the thermostat housing feel hot? do you have a Chicom infrared temp gauge?
If your HMMWV is truly running too cold you have a one in a half million truck!

I do have the numbers from one of CAMO's posts, but my temp simply hasnt gotten high enough to verify against those numbers.

I didnt feel the thermostat housing directly but I felt the upper radiator hose which did seem to get pretty hot.

 

[SmartDrug]

My 6.5NA can sit at idle for a LONG time before the needle starts to move, especially with the updated gauge/sender. If I start to drive it, though, I get to operating temperature in about 2.5 miles, driving at 25 mph (neighborhood). So it's slow as heck when sitting, but fairly rapid when under load.

 

[Autonomy_Lost]

After googling this, it seems like diesel engines generally dont warm up just sitting at idle. Apparently they really need a load to generate enough heat. Trouble is my truck is not street legal yet. I have access to a pretty large parking lot though, I will see if I can drive it in circles for some time and see what happens.

 

[Milcommoguy]

Yes to the cold blooded engines. Outside and 70...seems like forever at an idle. Got to drive.

Reference only. Resistance +/- to get the military gauge to read shown value. Where did you get sender? You should be seeing 180 degrees something. Stock thermostat, and fan disengaged?

2.5 K pot and dial it in. 1/2 watt perfect.

OPEN circuit = no reading
Short circuit = full scale
120 degrees =2250 ohms
160 " = 1700 ohms
200 " = 890 ohms
240 " = 640 ohms

Wait till winter, freeze one's butt off, CAMO

 

[Mogman]

According to CAMOs numbers the gauge should be reading around 170-180 @ 1.28K

 

[Gcelevator]

After googling this, it seems like diesel engines generally dont warm up just sitting at idle. Apparently they really need a load to generate enough heat. Trouble is my truck is not street legal yet. I have access to a pretty large parking lot though, I will see if I can drive it in circles for some time and see what happens.

When i started driving my truck around the block (not tag at that time) i never heard the fan kick in i thought was quiet until i went for a longer trip. Around the block it never raised to 180 degrees. Not sure it will do in a parki g lot.

 

[Autonomy_Lost]

I ended up driving it around the backyard (yes you read that right) for about 20 minutes and it finally got into the middle-ish of the green zone on the thermostat. But as soon as I stopped and let it idle again, the temp came down to the lowest part of the green band. Seems like it just wants to stay cool, I guess that's not the worst thing?

 

[Milcommoguy]

Did you check for proper fan operation? If the fan is locked up... system wonky, it would be hard to get it to heat up. Not seeing it IMO and a guess... fan is hung up due to all things fan operation. Never read was working correctly. (may have missed it) Or has been messed with. Thermostat in place or...missing. Stick a cooking thermometer in the flow tank when hot and see what you got?

Somethings to check, CAMO

 

[Autonomy_Lost]

Did you check for proper fan operation? If the fan is locked up... system wonky, it would be hard to get it to heat up. Not seeing it IMO and a guess... fan is hung up due to all things fan operation. Never read was working correctly. (may have missed it) Or has been messed with. Thermostat in place or...missing. Stick a cooking thermometer in the flow tank when hot and see what you got?

Somethings to check, CAMO

Good suggestion on the fan, I'll inspect the clutch and see if its working.

I have no clue about the thermostat, but that was my first thought. Its an auction truck so who knows. Honestly I'm not sure how to diagnose a stuck open thermostat other than by observing the symptoms. I could remove it and do a phyical inspection, but at that point I would just end up installing a new one. Which maybe I will do. I just dont like throwing parts at problems before I fully understand them.

As for a thermometer in the overflow tank, can I really run the engine with the cap off the tank while its at temperature? I'm thinking IR thermometer at the thermostate housing might be more practical?