just picked up a 98 cherokee local to me pretty cheap, found out combustion gases were leaking into the coolant. i replaced the head gasket, head was checked an planed. Jeep runs smooth,but over heats almost instantly. all air bubbles looked to be burped out. water pump an thermostat were both new before i got the jeep (previous owner must of known about the issue an replaced those). its not my daily, more of a trail rig but id like to get it running cool. only other issue is if i rev it up while adding coolant it'll basically start to spray out, but if i let it idle an squeeze the hose its fine. wondering if something is causing pressure / super heating the coolant. any ideas?

 

Fill it up with coolant. Let it reach operating temp. Turn off let cool down. Refill with coolant if it take any. Keep a check on coolant. Make sure you always do this with the heater on high.

Hopefully he replaced with a good T-Stat. You should use a factory T-Stat. The others are not worth anything really for consistent temps and are prone to failure. This is the part number I think. Double check though. 52028186ac

Also make sure the radiator ain't clogged or leaking. Might should do a flush on the radiator and heater core to make sure they are as clean as can be.

Also does yours have the fam shroud?


BUT......

if it's over heating immediately like you daid I would supsect the T-Stat is stuck, it's not filled full, or there is an air pocket.

 

I used to just fill it up, run the Jeep with the cap off, keep adding coolant as needed, and when it starts to bubble out shut her down. Get the overflow tank where I wanted and then drive around keeping an eye on it for a few days. All the air would burp out and I would get the levels where I wanted them.
Then I bought this:


30 to 45 minutes in my driveway and am good to go. When using it make sure there is always some coolant in the funnel. Keep the RPM around 1500 while doing it.
Works like a charm for me.

I have read the horror stories when it comes to thermostats. 6 years ago I bought the cheaper one at Napa. Works fine. As a matter of fact I just did my water pump and opted to not replace it. I did buy a new one (just in case), Stant Superstat, but did not use it.
One thread I read a guy went through 4 that were defective. The 5th one being the charm. Another guy was saying he went with a Mopar one that was defective from the get go and replaced it with a Stant that worked like it should.
Maybe I just got lucky with the cheaper Napa one.

 

I've never used anything BUT Stant since I learned to drive in the early 60's and never had a problem with one. Oh, I've had problems, but it wasn't the t/stat.

The best method I've found for filling the system is to remove the temp sensor near the t/stat and fill it until coolant flows out the hole. Install the sensor and finish filling. Run the engine until the t/stat opens and top it off. Install the rad cap and fill the reservoir a little above the full mark. Done! Check the reservoir level the next day.

 

You can't even trust Stant anymore. I had one that went bad about a year after putting it in. The best thing you can do is buy a thermostat and hope for the best.

Agreed with Chick, make sure the heater is on high and you are getting hot air from the heater. It can take a little while for the air to work its way out of the system.

Also, how "immediately" does it overheat from cold?

 

I'd flush the heck out of it and do the mopar t-stat just to be sure. Run the garden hose through the t-stat area, radiator and heater core, do the flush chemical (like Prestone) and a few passes of distilled water. Good to do anyway since it's a newly acquired rig.

I'm assuming that when you had the head off you didn't see any/took care of any clogged coolant passages, right?