Hey guys my cherokee seems to run at an unstable temp after i replaced the t-stat and fan clutch. It gets up to 205 and then quickly drops off down to as low as 180, builds back up to 205 and drops off again. I tried to get a Chrysler t-stat but the closest dealer to have one in stock was over 1 hour away. Used a duralast from autozone because it has the weep hole and I positioned it properly at 12 o'clock. I'm assuming I've just still got some air trapped in the system. Warm-up time is reasonable. I made an emergency water pump change a couple weeks ago (water pump started weeping on a cross country trip). I didn't have time to replace the t-stat and fan clutch at that time so I saved it for now. Jeep ran a rock solid 210 with the new water pump. This new t-stat and fan clutch are fluctuating the temps a bit, but she never runs over 210 (doesn't fluctuate much in town, only on the highway). Only have taken it on a few short drives and it's still pulling fluid a bit from the overflow tank. What say ye, still just some trapped air working its' way out? Thanks

 

I suspect you'll be happier with a SuperStant (not the cheap Stant) thermostat in there, or a NAPA. Doesntlast parts are generally on my "avoid" list.

 

Sounds like the stat is bad.

 

I buy plenty of aftermarket parts but the thermostat isn't one of them. I use only MOPAR stats. 195 degrees is the best temperature spec for the 4.0 stat for the vast majority of applications.

Get one of these installed and your instability will likely be over. The problem is not likely air in the system; 91-01 will burp themselves generally in 3-4 complete heat up / cool down cycles.

 

is the aux fan kicking on and off when this happens also?

 

I've had failures of three Super-Stats. Only Mopar now. My Jeeps would take forever to warm up in the winter with the 195 Super-Stat.

Mopar # 83501426.

 

Thanks guys. I replaced the factory stat with a Stant (no weep hole) that would not allow the engine to reach 210. Then I replaced the Stant with a duralast that now fluctuates. Guess it's time to make the drive to get the proper Mopar part. My factory one gave me rock solid 210, but it was starting to take a long time to warm up and with winter approaching in Indiana and seeing how I just changed the waterpump figured I'd get everything on the same page. As for the aux fan it never kicks on. Like I said ran rock solid 210 (but had an increasing long warm up time) before replacing t-stat and clutch fan. I've gotten away with buying aftermarket parts for years, guys this isn't one of those cases though. Alright, now to make the drive to get the proper Mopar part. Thanks guys!!!

 

The closest dealership to have the book listed p/n for my 96 cherokee was over an hour away. However I gave a local dealer the p/n of the t-stat I pulled out of the jeep (52028186). The dealer told me that is only listed for a 96 Grand 4.0L but a 4.0 is a 4.0 and it was working in my jeep so I installed a new Mopar t-stat with that p/n. It fluctuates a little between 195-205 but that's within operating limits and seeing how I just installed a new fan clutch it makes sense to see more needle movement than before with the old fan clutch that was clearly a bit sluggish. Thanks again, now to track down an intermittent belt noise. Gonna replace the idler pulley, had one seize up in a Ranger and the belt tension threw the pulley on top of my new batt and the super hot pulley bolt melted through the top of the batt case. Don't want something like that happening again, not over a $28 pulley. Thanks again, I've learned when in doubt go Mopar. Advanced and Autozone have both let me down for the first time in over a decade!!!

 

Why would a 195 t-stat make it run 210?.....especially if ambient temp is cool and heater is being used. Have u installed a new rad cap? Coolant recovery system will not function correctly and/or the system will not "burp" if the rad cap is not functioning correctly. 180-205....some folks can only dream about/wish their XJ ran those temps. Testing the stat would be a lot easier and way cheaper than 2 hrs worth of gasoline, no?.

 

Gauge could be little off. Like my altimeter runs 14.6 but my gauge runs 11-12