Ummins ISX15 Random Overheating

[in2trux]

(10-25-2016 )gatow900 Wrote:  Rereading your post if a/c stop blowing cold air you engine fan stopped working. Check the air line going to fan clutch and fan solenoid.

The fan should default to always on if the solenoid loses power, I had that problem yesterday.,dirty connection.

Overheating while idling has to be something stopping the coolant flow ,like a bad tstat not opening or a slipping belt maybe not driving the water pump. Check belt tensioner and pump . I never had a truck overheat idling. Just because a part is new doesn't mean it's good, especially tstats.

With a new fan clutch and tstat,you would think they checked to make sure it was cycling properly.
You say the a/c went hot, check that compressor didn't seize and high pressure cutoff switch, can't see that causing it to overheat.

I'm with Rawze on checking fan direction.
Some of the people fixing trucks have trouble pumping gas.