6.0l Slow Thermostat?

[terryk]

I have a 2000 2500HD 6.0L and noticed that unless there is a load on the engine, the coolant temps will drop off into the low 180 range. If the engine has some load it will rise to 195 (on the scanner) and stay there. But if I go down a long hill it will drop off to the 180 range and then slowly come up (over maybe 5 minutes).

 

I am thinking one of three things are happening:

 

1. The radiator is so huge that it sheds heat far faster than the stat can close to get the temps up, or;

 

2. The thermostat is slow to close, or;

 

3. The fan clutch has just enough drag when disengaged to over-cool the radiator.

 

Or maybe this is normal? I want the temps to stay up at 195 range but it just won't. The fan clutch seems to be working fine and not engaging when this is happening (you know when it engages..). Maybe it has just enough drag to over cool the engine but not sound locked up?

 

On hot days, the temps do pretty much stay right at 195F or so and only vary when I am towing (highest I've seen is 221 climbing an 8% grade in second at 55MPH dragging 8000lbs. When the road flattens out, they drop right back down).

 

Overheating has never been an issue even on the worse of days towing 8000 lbs.

[txab]

OEM t'stat is 186 degrees. it should keep you pretty close to that for the low side. You could have a t'stat that's getting a little lazy. How long has it been installed?

[terryk]

OEM t'stat is 186 degrees. it should keep you pretty close to that for the low side. You could have a t'stat that's getting a little lazy. How long has it been installed?

 

I don't know. I have a new one to install, I was just curious. I looked at the new one and it's 186 as you said so this actually makes more sense now. It's not as dramatic as I thought. There is obviously a differential between the coolant sensor location and the stat. That is similar to my son's Z24 Twin Cam. It has a 180F stat and the coolant pretty much stays at 195.

 

I'll replace the stat and move on with life.

 

Thanks!