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Old August 11th, 2017, 20:40
Slimer Slimer is offline
NAXJA Forum User
Join Date: Jun 2017
Location: Tempe, AZ
Posts: 91
Re: Temperature jumping from warm to hot and back again

Originally Posted by Tony the Liger View Post
Just completed the following on my new-to-me '00 XJ: replaced the valve cover gasket, a pinion seal, steering stabilizer shock, two axle U-joints, one wheel cylinder, and one set of brake shoes. On my way home from the garage, the XJ started to overheat a bit.

This is the first time it has overheated on me. I've only had it a few weeks and haven't driven it much, but I bought it in a town that's around three hours away from me, so I drove it around town and on the interstate for well over three consecutive hours on the day I bought it and didn't experience any overheating whatsoever. After warming up today, the temp sat just a hair past 210, then gradually climbed to the first notch past 210. I made it home by that point and parked it for a couple hours. After letting it sit, I took it up the road and back, and in that time the temp climbed to the same point, sat for a few minutes, then out of nowhere it spiked to the notch below 260. It sat there for a few second, then dropped back to just above 210. Sat for a few more seconds, then did it all over again.

Hoping the thermostat's sticking and I can get by with a $12 or so fix. Any thoughts?
After extensive testing with my overheating XJ, this is pretty standard. If you look at my thread on the very same issue you can see the video I posted.

What is happening is that the stock gauge in the dash is not very accurate. Your engine is probably actually running about 240 all the time like mine is. When it finally hits 260 the check engine light comes on and the gauge shoots up almost simultaneously. When the thermostat then opens and pushes the cool coolant from the radiator back into the block it is just enough to send the gauge back down out of the red. My gauge basically doesn't read anywhere in the upper 2/3's of the gauge. It runs just to the right of center and then shoots over to just below the max temperature.

I finally figured this all out by doing what RCP Phx told me. He said to order a cheap meat thermometer off of Amazon with dual inputs. The inputs are very thin and can easily fit in the hoses with the wiring leading out under the clamps back to my interior. I put the probes in every hose that I could and drove around and checked out the temps. My Jeep runs hot no matter what I do.

I just orderd the fancy Hesco Water Pump and the Griffon Radiator. Hopefully that solves my issues. I have replaced everything else.
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