Changing the Thermostat on a Jeep Cherokee

Changing the Thermostat on a Jeep Cherokee

Janice’s 1999 Jeep Cherokee has had a small water leak for a few weeks now. We finally tracked it down to a leak at the thermostat housing. I decided that since I would have the housing off, I would also replace the thermostat. I decided to use the Mr. Gasket one like I put in Scott’s Wagoneer.

I had forgotten how much easier the thermostat is to access on the later model engines since I rarely work on those. On the earlier engines the belt is right in the way of accessing the bolts. On the 1999 the belt is routed differently and is not in the way at all. I did unbolt the fan shroud to get a little more working room, but I am not sure that helped much.

The housing is held to the block by two 5/16 bolts with ½ inch heads. I removed the two bolts and the housing popped right off. I had to use a screwdriver to pop the old thermostat out of the recess in the front of the block.

Cleaning the front of the block took a while. I scraped old gasket with a scraper as much as possible. I finished up with a Scotchbrite wheel in my drill. To clean the housing, I chucked the Scotchbrite wheel in my drill press and brushed the surface. I polished part of the outside of the housing while I had it in my hand.

I had a little trouble putting it all back in that the thermostat did not want to stay in the recess. I made sure that the bleed hole was rotated to the top and pressed it in. It would fall back out each time. I finally put a few dabs of RTV on the flange and got it to stick long enough to set the gasket and housing over it.

I then tightened the bolts and refastened the fan shroud. Then I put the radiator hose back on and tightened the clamp. I left the heater hose off and used a funnel to fill the head with coolant until it bubbled out the radiator cap. I then installed the heater hose and finished filling the system through the cap.

UPDATE: The new thermostat failed immediately on our Thanksgiving trip. I did not notice it until it started getting cool out and I wondered why the heater was not working. Then I noticed that the temperature was much lower than normal.

When we got back home, I pulled the thermostat and found it was stuck open. Better than stuck closed but still not acceptable. I returned it to Autozone and they swapped it for a new one with no hassle. I still had to buy another gasket to install the next one. Before installing this one, I put it in a pan of water on the stove and made sure it open and closed properly.

She says her Jeep is now running at normal temperature and the heater works again.

Update: I recently changed the thermostat on my 1991 Jeep Cherokee. The belt routing is different and makes the procedure slightly different.

Mr. Gasket PERF THERMOSTAT GM-195 – 4365

Mr. Gasket PERF THERMOSTAT GM-195 - 4365

Mr. Gasket PERF THERMOSTAT GM-195 – 4365

MPN #4365. Mr. Gasket PERF THERMOSTAT GM-195. Most Cooling and Heating products are available for in-store pickup from Advance Auto Parts.