So, I have a new radiator, water pump and thermostat and all connections have been checked. My temp will sporadically go from 210 to almost redline then back down to 210 then sometimes stay at a notch below the redline for a while then drop down to 210 for no reason. I have heard air pocket/bubble when filling up new radiators can get trapped in there throwing off te thermostat. How do I remedy this besides fully draining it?

 

The old fashioned way is to pull the upper heater hose and fill until it spits out the upper heater connector, then do the same with the top radiator hose until you get coolant out the upper radiator port. Shouldn't have to do that with a 2001, just fill, run it until the thermostat opens, let it cool, top it off and go. What did you use for a thermostat? Some have issues with the 4.0.

 

Here is the thermostate I put in:

http://shop.advanceautoparts.com/web...023%7CL3*15971

 

That t-stat may be your problem. Many people have problems with after market t-stats on the 4.0. Try an OEM from the dealer it will be a couple of dollars more. Also when you fill your rad. Fill it and run it with the cap off to get the air out of the system and top it off. On the newer XJ's the air should come out after a few cycles of running the engine. Just keep an eye on the coolant level for a day or two of driving.

 

Did u install a new rad cap? System will not burp/recover with a bad/old rad cap. And as stated, u gotta let the motor idle, with the rad cap off, keeping the rad filled, 'til the stat opens and top rad hose is hot, then u install the new rad cap. For several days afterwards, check coolant level (motor COLD) by removing the rad cap. top off as needed and check the recovery bottle....it MUST ALWAYS have coolant in it, motor hot or cold.

Poor ol' "Made in the USA" Stant SuperStat always seems to get a bum wrap.

 

I just tried one again for shiggles since I had it lying around. The last 195* SuperStat I used actually seemed to be a 182* as that is where my temp hovered. This current is working really good, maybe keeping my XJ just 2 or 3 degrees cooler than the Mopar I had in the past 6 months.

I also have 180* SuperStat lying around as I remember you saying you run with that temp.

 

Yep, 180 SuperStat been in 3 1/2 years now.

 

thanks for the replies guys, I will try a new stat

 

On a stove, with the stat in a small metal pan with enough water to cover the stat and a cooking thermometer just test it......won't take 10-15 mins. If u do buy a new stat, by all means test it before u install it. Don't drop it in boiling water.....it's not exposed to boiling water inside the motor (hopefully).