Engine Temperature Hi-jinks

[Ajax MD]

I'm still planning a coolant flush and a thermostat refresh, but it appears that the hot running issue in my wife's HMMWV is more a case of the temperature gauge being off by 10-15 degrees.

First, I have observed that the engine seems to be running cooler in general, down to an "indicated" 215F from 230F but when I shoot the engine with a no-contact IR gun, the whole engine reads 189F-197F except for right in the area of the T-stat on the crossover pipe which indicates 205F. As soon as you move around on the crossover pipe even a couple of inches in either direction, the temperature drops into the 190's, 200F max. I can leave my hand on most parts of the engine for extended periods without being burned so there's no way

This checks with the fact that the fan clutch engages at what you expect to be the proper temperature even though the gauge indicates a fair bit hotter. The engine only gets that hot if I run it hard on the freeway...which we will hardly ever do again.

I dug another golf ball sized mud dauber nest out of the heater ducting.

Maybe I'll throw a new gauge sending unit in the engine while I have the coolant drained. If the gauge still reads high, I'll replace that next.

 

[DREDnot]

Sounds like a solid plan. I plan on doing a full cooling system refresh with all new OEM sensors and thermostat soon just to be sure everything is top notch cooling wise. I am not a fan of seeing 230 on the gauge either

 

[papakb]

These gauges are made by the lowest bidder and aren't always of stellar quality. I had an oil pressure gauge fail at one of the Portland shows and it took me 3 gauges that would match the readings I was getting on a mechanical gauge plumbed into the same location. Of the lot, the voltmeters seem to at least be somewhat consistent in their readings. This and the Stewart Warner gauges seem to be slightly better than Faria.

 

[Ajax MD]

@papakb I totally agree that S-W gauges are of higher quality.