Join Date: Mar 2014
Location: Honaunau, Hawaii
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air still and again in cooling system
Need some advice from the experts and those who have traveled my same road. I apologize in advance for the length of this post - I wanted to be pretty specific about what I'm experiencing.
2008 Clubman, N12 (70K miles) had major leak in thermostat housing and engine went hot enough before shut down that the seal grooves around the center 2 bolts in the valve cover distorted.
I replaced the thermostat and housing along with water pipe which also had some deterioration where it meets the water pump housing and a lot of sludge buildup in the tube. Had to use RTV sealant on valve cover to keep #1 & #2 spark plugs free from being surrounded by oil.
Having read numerous posts here about bleeding the air out of the system, and having talked to the service manager and a mechanic at BMW dealer, I am still getting air in the system.
I have bled the system with heater on, waited for coolant at bleed screw and then topped up reservoir. After a drive I find heater starts to loose heat. Open hood and reservoir is now full with both upper and lower radiator hoses rock hard until I again let the air out of the bleed screw and then reservoir drops to normal level.
Also as I drive, sometimes temp warning will come on and then go off shortly. Sometimes it will not come on at all. It acts like the thermostat stays closed too long and then problem clears when it opens.
Why can't I keep the air out? Is it possible that head gasket is allowing compression gases into cooling passage? Have I possibly reversed the upper and lower hoses at the thermostat housing? Water pump no longer pumping?
Confusing part is that system never seems to overheat and stay overheated. Warning light always goes off after a few seconds but reservoir gets highly pressurized.