1990 XJ Cooling system ?

Have a 1990 Jeep Cherokee with the 4.0 and an automatic. Question is.. If I start it, and let it warm up, it'll get to a temp of 210. Will not over heat. Then when I start driving, it will start fluctuating between 210 and 165. Whether the heat is on or off. Whether the defrost is on or off. The coolant level is fine, I just did a thermostat on it yesterday night, refilled and bled the system. And it's still doing it. If the heat is on, when the temperature drops, the heat inside the truck is noticeably cooler so that leads me to believe it's not just the temperature sensor. Any ideas as to what would cause this? Belt is tight and all, not sliding around on the water pump. No coolant in the oil, no missing coolant at all. Just looking for ideas as to where to begin before I waste a bunch of money on parts I didn't need.

Thanks in advance,

Jer

waterpump it's self is bad?

Double check the Thermostat..... I did the thermostat on Liz's 240, And it still over heated, ended up getting a new bad thermostat.

The only thing I can think of is that there is still air in the system or, that the thermostat was put in backwards or is defective.

Quote:

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Originally Posted by Flicktitty

waterpump it's self is bad?

Double check the Thermostat..... I did the thermostat on Liz's 240, And it still over heated, ended up getting a new bad thermostat.

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Not overheating, underheating.. if that's a word..

I had it cold, cap off, ran it until it got warm.. and right around 190 deg the coolant dropped down, had heat in the truck.. So as far as I see.. the thermostat is opening fine.

Quote:

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Originally Posted by Prince Valiant

The only thing I can think of is that there is still air in the system or, that the thermostat was put in backwards or is defective.

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Thermostat was put in, spring inside the engine as per the manual.

I guess I'll try burping it again.. Maybe I'll just have a coolant flush/fill done so it's someone else's problem to make sure it's right.

Try another thermostat, preferably a different style/brand. I have had trouble with some brands not working the same, not working right, staying open too long, or simply having way too big a bypass hole in them.

Guys on Naxja told me to try burping it again by taking off the top hose, filling it there, then jack up the front of the truck and burp it. Said it's worked best for them, so I'm off to buy coolant and probably another thermostat.

EDIT: More research, finding another guy with identical problems.. I guess my best bet is to put a prestone flush and fill Tee in the uppermost heater hose and burp it with that.

Did you figure this out? I had these symptoms last spring but I was losing coolant and it turned out to be the freeze plug :(