Our 96 Accord LX 2.2 AT started overheating on a trip into the mountains last weekend. We found that the valve in the middle of the radiator cap had broken off. The cooling system wasn't pressurized and the coolant had boiled out. Also, we had a waxy, plasticy substance inside of the radiator.

We replaced the radiator cap with the correct 1.1 cap and added antifreeze/water. Everything was fine for two days. Now it overheated again! The middle/center piece is missing off of the radiator cap...again.

We've checked the oil. It looks good with no foamy, sludgy indications. No white exhaust. The heater works great, even though we really needed the air conditioner instead. The water pump was replaced at the same time as the belt about 20K ago. The car has 125K on it.

Has anyone had any experience with a cap breaking like this? If so, what did you find was the cause? Also, where do you bleed air on this engine? I assume at the thermostat housing which is on the front of the block on the passenger side of the engine where the top radiator hose attaches?

Thanks for any (good/related ) advice you can offer.

 

That isnt the thermostat housing, its just a water neck. The thermostat housing in on the back of the cylinder head, under the intake manifold. Air can be bleed from the rad cap, with the heater on full heat and low fan, in any position other the defrost