Open to the wider jeep community knowledge Base, I'm confused...
My Jeep Grand (2004 4.7l HO) bubbles air into the expansion tank when stopped after going on a drive.
It does not do this if run up, only after a few miles on the road.
About 2 minutes after switching off the engine there is a bubbling noise coming from the expansion tank accompanied by the expansion tank becoming overfilled but not enough to overflow. Whilst this is happening the top hose is hot to touch and feels empty.
After a while bubbling the expansion tank suddenly reverses and starts going down until it stabilises at the correct level and the top pipe feels like it is full again.
During the drive the temp gauge stays normal (just below 100) but usually creeps up to just above once stopped or if the engine is being worked hard.
It has not overheated or overflowed, the water level always stabilises to the same level (I haven't needed to top it up), the heating inside works fine and there is no evidence of water and oil mixing.
I have just replaced the thermostat (didn't cure it), the coolant is less than a year old as the rad was replaced late last year.
Got a head test done with a sniffer thing at the local garage and came up negative.
Anyone got any suggestions!? I take it this isn't supposed to happen?
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