I replaced my IAC valve a month or so ago. Before I replaced it, my engine would run in the 150-160 degree range. Since replacing the valve, it runs in the 200-215 range.

What's going on? I know the 200-215 is a pretty normal running temperature, but I sure liked seeing that needle sit at 160. Should a new valve make a 50 degree difference?

 

A little thing called Summer may be the culprit.

 

The IAC is not likely the cause. Something else is going on. The idle air control cannot change cooling system performance.

What is the history of "routine" cooling system maintenance?

*How old is the thermost, radiator, water pump, etc.?

*How often do you flush/fill the cooling system with fresh 50/50 mix of coolant and distilled water?

With cooling system, it's pay me now or pay me a lot more later. Cooling system maintenance is possibly the best money you can every spend on your XJ.

 

This was an overnight change. And my Jeep ran at the cooler range all last summer.

 

If something else is going on, then it happened the exact same minute I changed the IAC Valve. It ran in the lower temperature range the day I changed the valve. I changed the valve around lunch and it's been 200+ ever since. That's why I'm perplexed.

It never runs hot. If it ran hot I'd wonder if there was a problem going on. But it never runs hot.

 

On your 2000, the gauge is fed by the ECM which gets the data from the sensor in the thermostat housing. Best guess is you bumped it and its now showing the correct values.

 

Certainly a possibility to consider, with you working under the hood at the time you noticed the change.

Get a point and shoot thermometer. Widely available and inexpensive. Good tool for every mechanic to have. Point it directly at the thermostat housing of a hot engine. Then you'll know what your coolant temp truly is.

The coolant temperature sensor in the thermostat housing can be tested and or easily replaced.

 

Hadn't thought of this, but it's as good of a guess as any, and it actually makes sense.

Good advice. I'll head out today and pick one up. Thanks guys.

 

To prove if it is or isn't the IAC, put the old one back in and see if the temps go down. Lol