cmahaff

Hello
I know this topic is beat to death. I've been reading a lot of forums. I can't seem to find out where to start on my particular issue.

98 Cherokee. Stock cooling system.
water pump and thermostat was replaced. But not too sure how long ago. Probably within 10k miles. Thermostat should be 195.

When I'm climbing mtn hills my engine temps go up. With no AC on. If I baby it, maintain a slow speed and turn the heat on I can keep it around 227.
Subsequently, when cruising on a sustained downhill, it will typically drop below 170.
This is what's confusing me. The fluctuating.
Doesn't seem to make a difference whether it's 95 out or 75.
Crawling up a rocky trail, usually stays at 210.
Pressure test indicates no leaks.
Today I drove around town for about 5 miles and it was 98 degrees. Stayed at about 210 and I noticed the second fan never turned on.
I'm hoping for a few tips on what to check first.

Appreciate it!

Cullen

Bugout4x4

This is what engines do if they have no thermostat at all. Some conditions will make an engine heat up too much if it doesn't have a thermostat because the coolant is flowing through the radiator too fast to cool. It isn't in the radiator long enough to cool before being reheated again. The thermostat also works as flow control. Sounds like it's time to just toss a new T stat in it to be sure that question is eliminated.

BlueRidgeMark

Might need to be burped. Can't hurt, and it's free. A new, TESTED ON YOUR STOVE T-stat is pretty easy and cheap, too.

Bugout4x4

Something else I didn't catch yesterday is this Mark...

"Stayed at about 210 and I noticed the second fan never turned on."

Sounds like its time to purposely test this. If it's not getting warm enough to kick the fan in he might need to put something in front of the radiator to block it off and make sure it comes up to the temp the fan is supposed to kick to make sure it is indeed working or not.

But the running at a 170 degree temp has my attention with this. Either the sensor is reading air as you suggest, The sensor is bad, or the T stat is not present or working correctly.

cmahaff

Thanks for the ideas.
I'll order up a new thermostat and burp it and report back any changes

Cheers

outersketcher

you might want to get a thermostat with one of those little holes in the plate.. or drill one there yourself to let any air burp through it an out.