1987 Jeep Cherokee
L6 sealed cooling system
Problem sitting at Idle, coolant fluid forced out of pressure tank. Gauge temp indicates 200-210 degrees. Have replaced plastic pressure cap, pressure tank, water pump, fan clutch, many thermostats.
Took to dealer mech. Bad mistake, I had to do much of the troubleshooting for them, but did say I had no head gasket leak. The dealer informed me it was the fan clutch. Replaced did not solve problem.
Also, water temp into radiator 210 degress water temp out 118 degress so the radiator seems to be doing its job. I believe the problem to be in the motor, but where?
By the way as I am tooling down the road in my jeep my temp is normal about 170-180 degress.
Help!!!

i had the same problem after replacing the thermostat. Turned out i had cracked one of the rubber hoses at the base under the clamp so the leakage wasn't as obvious cuz the spray was hitting the manifold, evaporating it. When it was idling, it leaked onto the block where it pooled, with only slight leakage hitting the ground.

Just an idea. If there is no antifreeze on your dipstick (cloudy sludge) then i doubt the head is cracked.

Checked system for leaks, found none. Had mechanic pressure check cooling system OK No leaks Thanks I gave it a shot.

I am going to replace plastic pressure tank cap it seems to slip when I tighten it down.

I just bought (at auction) a 88 Cherokee with the 4.0 engine...
The resovior tank was stained so I knew it had a problem overheating... As I was ready to call a toll truck & give up I kept topping off the tank, I think the engine had a air lock which caused the overheatng...
You might also check you heater coil (carpet will be wet)
Bob

You maybe right! Installed new plastic pressure cap on the resovior tank. Wife drove jeep all day temp ran about 200-210 on gauge, but know coolant came out the cap on the resovior tank. I am hoping that there is air in the system causing it to run hot. I will check in the morning and add more water.