ok guys i just did a radiator flush and replace my thermostat because it was running a little hot and when i turned my engine off the coolant bubbled and over flowed and started pouring out in my overflow reservoir. first question why did this happen? now with the thermostat replaced it doesn't over flow but when i check the reservoir after running it for a while it looks high, not at the top but above the full line and i filled it just below the full line and topped off the radiator. it also doesn't over heat the highest the temp guage goes is 210. why does the coolant in the reservoir fill up? is there a clog somewhere? i thought the thermostat was the problem. i would appreciate some input thanks guys.

 

I don't know much about this and have never ran into this, but whenever the engine is off and cools down, the coolant will run back into the overflow obviously. Did you try removing some antifreeze and see where it goes from there?

 

It's called pressurized coolant recovery system. The cooling system pressurizes (presuming no leaks and good rad cap) as motor heats up. Once pressure reaches the rad cap rating, some coolant will escape the top of the rad under the cap and is captured in the recovery/overflow bottle. As the motor cools pressure drops and coolant is drawn from the bottle back into to radiator. The rad cap is critical to the process as it's a 2 way valve. Coolant rising a little in the bottle (as motor heats up/system pressurizes) and falling a little (as motor cools) is normal. If coolant is released out of the system (onto the ground) air replaces the lost coolant in the system and that is not good. Raise those hoods weekly....check things out.

The bottle should be filled to the low mark when the motor is COLD. The rad should always be full.....check when motor is COLD.

 

210 is normal operating temp for a '95. That's not a problem. If the XJ is running hotter, than you have a possible issue. And I'm not talking a tick above 210 either, This isn't abnormal under stresses such as running the a/c in slow traffic or stuck in construction lanes during the warm months.

If it is, it could be something as minor as a thermostat or something more severe such as a head gasket.