99 XJ 4.0, auto, 2wd with 180k. Live in TX and air temps have been 95-98 outside this summer and my temp gauge has been at 220ish ever since the hot temps have hit. Last week i shut the jeep off and you could smell and hear coolant "boiling", popped the hood and it vomited a large amount out of the recovery tank overflow. Replaced my radiator cap thinking that might be it and filled up the radiator and recovery tank again.

Fast forward to yesterday, jeep still running 220 and no coolant vomits for a week. Did a short highway drive and parked her at the store. Came out and restarted, overheat all the way to red. Shut her off within a few secs and came back later last night. Checked coolant and it was full. Confirmed electric fan was cutting on and working.

Just wondering what these symptoms might be saying? I'm replacing the fan clutch, water pump, thermostat, and radiator today just to eliminate those form the equation. I'm also going to do a full coolant flush with treatment chemical today. Could this haven been an air gap issue due to the coolant vomit last week?

 

Did you fill resi tank "full" or just to full mark??

 

Fill.

 

Then you probably had the bottle too full. There is a mark on the side of the bottle for full cold. If it is over that mark it will belch on opening of the thermostat if the rest of the system is full.

 

rebuilt full system and problems ended. thanks!

 

Good.

Most likely a flaked-out T-stat.

 

That's good to hear!