Remus Redbone

95 Cherokee SE, 4.0L auto trans, 161k miles.

First, I don't have an overheating problem. I did have a few weeks ago, but with a few system flushes, a new water pump & thermostat, that's fixed.

I've been driving the Jeep almost daily with no signs of overheating. The aux cooling fan is working properly, comes on with the AC, and occasionally if in line for fast food or slow rolling off road.

I just added a factory gauge cluster with new Borg-Warner sending units for oil pressure & water temp. Oil pressure looks good, but the coolant temp is definitely SHOWING too high on the gauge. The gauge has a midpoint at 210F and a max at 260F. The mark halfway between those two should be 235F. The Jeep is running slightly above the 235 mark on the highway and into the red (240-250) when the aux cooling fan comes on.

An IR laser temp gun shows 202 - 208 on the threads of the temp sensor in the thermostat housing and 204 - 210 on the threads of the sending unit in the head. Those are the readings after coming off the highway & leaving it idling.

Is there a way (other than trying a dozen sending units) to calibrate the temp. gauge to show close to what the IR laser temp gun is showing?

CCKen

Is this the temp sending unit you installed at the rear of the head?


http://www.rockauto.com/en/moreinfo....sn=233&jsn=233


Mopar part number 56027012.


There's no way to calibrate the gauge,

Remus Redbone

Yes, I replaced the gauge sending unit that threads in to the head at the driver side rear, but I didn't use the one for which you sent the link. I used a Borg-Warner WT430.

Remus Redbone

Solved: I opted for the more expensive / considered higher quality, Borg-Warner water temp sending unit when I upgraded to the factory gauge cluster. When I was seeing a very high temp on the gauge (250+) and very normal temp with my IR temp gun (~200), I went back to O'reilley's and picked up a Master Pro sending unit which was $5 cheaper. Now the gauge sits just slightly below 210 when the IR gun is showing 205-210 on the threads at the base of the gauge sending unit and 200 at the base of the ECM temp sensor.

So, when at a given temperature, the resistance value of the Master Pro sending unit makes the gauge point to the correct temperature on the gauge scale.

When the Borg-Warner sending unit was at any given temp, it was lower resistance than the Master Pro, causing more current to flow to ground & subsequently causing the gauge to deflect to a higher reading.

Sure doesn't take much to make things work right (or wrong).

Remus Redbone

See post above.

CCKen

Good work. Thanks for the follow up.