Temp Shows False Overheat??

Hello

My Cherokee has always read about 210 degrees at normal operating temperature. lately, the temp has been displaying around 240-250. I brought it to my mechanic and we checked the temp with a temperature gun he uses, and it was normal. Hoses were around 190, the bottle was about 160 the block was about 230. I recently replaced my Temp sender at the rear of the block and I didn't have the right size socket to tighten it all the way, so I drove it for a few days and when I finally tightened it all the way is when I first really started to notice it. does it make a difference how far the sender is screwed in? does the temp of the block have a huge impact on the temp sender?

It has been very warm here in international falls the last few days too though, about 90 degrees

-danols

You might want to check for air in the coolant system.

When you take the wire off, does it go to zero?

What about the the thermostat? Could it be malfuntioning?

How soon after startup does it reach the 240 deg. mark?

Hello! Thanks for the reply!

When you take the wire off, does it go to zero?
What about the the thermostat? Could it be malfuntioning?
How soon after startup does it reach the 240 deg. mark?

Yes it does go to zero with the wire off

My dad and I are going to replace the thermostat tonight or tomorrow

Well it warms up as usual, I live about 8 miles from my town, and I would say that about 3 miles in it is up to 210, about 5 miles in, it is at 240, and about 7 miles in it is anywhere between 210 and 240.

I am now wondering if I got a bad Temp sending unit when I swapped my Dash Cluster. If I do replace the sender, I have noticed that many people use the sender hole to burp the coolant system, and I am curious how you get all the air out?

Thanks- danols

Hello! Thanks for the reply!



Yes it does go to zero with the wire off

My dad and I are going to replace the thermostat tonight or tomorrow

Well it warms up as usual, I live about 8 miles from my town, and I would say that about 3 miles in it is up to 210, about 5 miles in, it is at 240, and about 7 miles in it is anywhere between 210 and 240.

I am now wondering if I got a bad Temp sending unit when I swapped my Dash Cluster. If I do replace the sender, I have noticed that many people use the sender hole to burp the coolant system, and I am curious how you get all the air out?


Thanks- danols

That is one way that some people burp the air out, but I will tell you how I do it so that after replacing it, you don't have to worry about taking it back out:

First park the jeep so that it is slightly pointed uphill.
Fill the overflow tank to the correct amount, then put on the cap.
Start the jeep and let it run until it reaches operating temperature. You can tell when the thoermostat opens by feeling the upper hose, it will be hot, but you can feel the water flowing.
Shut off the jeep and squeeze the upper radiator hose to remove any air in the hose.
Once the jeep cools check the overflow bottle again, if the fluid level has lowered any, then top if off and repeat the procedure of warming up and shutting off the jeep.

This takes a while to do, but does a good job of removing all the air from the system without having to remove any parts.