majordamagexj

I have a 1988 cherokee with a thermostat issue, it runs very hot quickly, then the overflow tank starts to bubble and boil. Thinking I either need a new thermostat or have air in the system. This has one of the radiators with no cap. I need to know what kind of thermostat to replace it with or if yall have any other suggestions.

Scotty16

I believe the standard thermostat is a 195*

Pelican

^^X2. Stant Superstat or Mopar OEM.

Do you have an overheating problem?

Have you recently done some work on the cooling system? Otherwise why do you think you may have air in the system?

Scotty16

On my prevous 89, I had an issue where it would run hot. Ended up finding pin hole in the radiator...also if you haven't burped the system go enough air will stay there.

Look for leaks first (which I assume you've done, do it again and be thorough)

How does the coolant look? Is it green?

The oil, is it milky?

majordamagexj

I tried to flush the system about a month ago just for good measure, but the problem just got worse after the attempted flush...probably air in the system but figured i would change the thermostat too just in case...what about the cap on the overflow tank? should i get a new one of those too or does that not do anything?

Dfread

Changing the thermostat solved my problem completely on my 2000. I don't have a closed system but I know that you need to make sure you burp all the air. Not sure on the overflow cap though. Changing the t-stat (195) is cheap though so might as well try that before anything else, good maintenance item anyways.

Scotty16

If the cap is not tight enough then yes that can cause your xj to run hot, it did for mine, because it let the pressure out. You can buy a new overflow or cap too and see if that works. what id do first before buying it is see if your cap is loose or if t is nice a tight and stays that way

Renix systems are finicky. the previous owner of mine converted the cooling system to a open system.

cruiser54

Start with this^^. Go to Napa and buy a 703-1396 cap for your bottle.

Install it tightly and see what happens. I wouldn't be surprised if it fixes the issue.

Big David

I went thru tons of crappy thermostats before I got a good one on my 88 MJ.
Get one from NAPA or MOPAR.

cruiser54

Skip Napa. I got 4 bad Stant Super Stats from them.

Firestorm500

Sounds like a possible blown head gasket to me.

majordamagexj

I opened up the thermostat housing today...and guess what?!?!?! there was no thermostat in there at all!!!!!!! Was putting in the new one and then tightened the bottom bolt too tight and snapped the housing...going to get the new housing tomorrow and then we will see how it runs. appreciate all the input!

cruiser54

Not uncommon. What stat did you get? On a Renix Jeep, it helps to loosen the belt so you're not fighting it putting the bolts in.

Firestorm500

At least you didn't snap off the bolt in the head.

It still concerns me that you have a quick overheat and boil. It sounds like the PO took out the thermostat trying to avoid chronic overheating? I don't think lack of a thermostat would cause that. No thermostat means slower warm-up, or not at all, depending on outside temperature.

A head gasket blown into the water jacket does what yours is doing.

majordamagexj

All is well now, new superstat 195* is in. all runs good and nothing out of the ordinary. No blown head i dont believe