1990 ccherokee engine runs cool but coolant shoots back into resivior when engine is shut off

 

I have an 89 that I have changed to a newer style from a 91,but when I had the bottle I found when it did that it was due to air that got in the system from the cap leaking and sucking in air when it cooled down. It also happened when I had a slight headgasket leak that would pressurize the cooling system.

 

Well When the engine gets hot the thermostat opens when air hits that thermo. in your cooling system it closes and then you car will run not. You need to burp(get the air) out of your coolant system.