Long time no see everyone here! As usual great posts and answers from everyone. Has helped me out many times. But im very desperate now. Im travelling from San Antonio to New Mexico and my 98 cherokee, 4.0L, 2wd over heated 500 miles into the trip ! Temp gauge all day was at the normal 210 mark and I always monitored it. Next thing i know the check gauge light came on and temp gauge was right before first red mark. Pulled over and saw coolant bottle was filled and wanting to overflow. You can hear pressure in the system still and upper radiator hose was hot and could not squeeze. nothing coming from rad. cap and no other leaks anywhere throughout engine. took about 5-10 min to cool down and all the coolant in the bottle was now gone. I refilled system and kept going. temp gauge at 210. about 30 miles later it did it again. but this time I saw the check gauge light come on and then the temp gauge needled jumped from 210 to right before first red mark in a second. coolant bottle doing same thing. Let cool. Refilled system. Ran another 30 miles with heater on full. temp gauge under 210 all the way till i got to hotel. Is this a sign of a stuck thermostat? or something else. Im still about 100miles from destination but if problem simple enough maybe i can fix in parking lot. any tips to further check on? im desperate to hear something from anyone. luckily i dont have to go back to work till monday but checkout time is 12p. Help!

 

It could be the thermostat but I'm not sure. I have run with out a thermostat before in desperate situations.You could try that if you cant get a hold of a new thermostat where you are at,you have to try and save the old thermostat housing gasket if you try this. If you can get to a parts store might as well purchase a new thermostat and gasket for what they cost, if it don't work then at least thats ruled out as the problem. If it does work then you're on your way .

What do you mean by re filled the system? Did coolant leak from the "coolant bottle" or did you just add more to the bottle after the coolant was sucked back into the cooling system?

 

i added more coolant to the bottle and radiator. there was none left in the bottle. and could not see level at radiator cap.

 

there are a few parts stores here in town so getting a new thermostat and gasket shouldnt be a problem.

 

Have you checked the oil for coolant and elevated oil level?

 

And yea I would start with the thermostat first, they aren't very expensive.

 

just checked oil level and its good. oil doesnt seem to be milky or off colored either.

 

After running engine can i check upper and lower rad hoses to see if one hot and one cold to give indication of a stuck thermostat? Or is there something else i can try?

 

Thats good news .Just another idea,are your cooling fans working? I'm not sure about your set up since I am new to jeeps but my 99 has a clutch driven fan and an electric fan.I would also keep an eye on them to be sure they are working.

 

me too spoonman. i will check on those two in the morning. ill check back here about 7am mst.

 

I am not sure to be honest. The thermostat usually has a small bypass hole in it so you will still get coolant flow which would heat the upper hose.
I think that you are thinking of the procedure of checking for a plugged up heater core.

I would just get a new thermostat if I were you,They are simple and cheap to replace.

 

cool, keep us posted on your findings and progress. Good luck

 

When vehicle is about midway to normal operating temp (210 being normal) the upper hose should be warm and the lower hose should be cold. Once its at 210 the thermostat should open causing the lower hose to become hot too. This will let you know if your thermostat is good.

If the lower hose NEVER seems to get HOT and instead stays more cool and the gauge keeps climbing, then its possible the thermostat is stuck in the closed position.
If, again, its at midway temp to 210 and both the upper and lower radiator hose are already warm, then the thermostat is stuck open. For either one of these...Replace it.

And then, its also possible your water pump gave out...

 

Stats are designed to stick open but I have seen otherwise. Starting with thermostat is not a bad idea, as simple things first. 195 degree only. I like stats from Jeep and also the Stant SuperStat. Stay away from cheap stats!

Radiator cap often ignored. $5.00 Buy one

A clogged heater core should not create an engine overheat condition.

After that, for highway overheating on a 98, you are looking at a water pump problem, or possibly radiator restriction. If you dig in and do one of those items, do them BOTH.

 

The water pump was replaced a few months more than a year ago. Im going to replace the thermostat first thing today and see what happens and will report back. ill be checking here often so if anyone has their two cents to throw in, please go ahead...