remove the cap off the Coolant filler. Start the ngine and let it tick over until it reaches the normal temperature. Now watch for air bubbles in the coolant filler. If they appear rev the engine, and you will see the coolant level drop suddenly. refill the coolanr to the correct level and watch for more air bubles. repeat this until no more air bubbles show. Replace filler cap and road test.
You sure your radiator cap is working properly? Any chance it's "boiling over" because the cap is going way past what it should be venting at, and when it does vent, it's violent?
The ONLY thing that would blow hoses off is pressure (or a bad job tightening the hose) and if the hose came off from pressure, and was tight, I'd be looking hard at the radiator cap.
Subaru’s in your year range had a problem with head gaskets. You indicated replacing “A” head gasket, did you replace both sides? This is a flat design 4 cyl. engine with two differ heads. Also head gasket replacement on these engines require an unusual procedure, if not done properly problems will continue. Your descriptions suggest you still have a head gasket problem.
smell the coolant. If it smell a trace of exhaust then you have do the head gasket again.
check your elec. fans make sure they come on if not try check for power at the fan or bad fuses or ralays you can try bringing power to the fans if they work they are good and its a power issue if not then bad fan motors
My first problem was a boil over from the over flow, ok fine. So I changed the thermostat, same thing again and I boiled the thermostat in boiling water and it works. I changed a head gasket because there was trace amounts of oil in the coolant. My water pump seems fine as there are no leaks in the system at all. My rad hose kept coming off from too much pressure so it seems bit that is now fixed.
I had some people say its either clogged rad fins or air still in the system but that doesn't make a lot of sence but what do I know.
My car is a 99 Subaru legacy outback, 4 cylinder dohc with 317461km the coolant was bubbling a bit in the over flow at 313671km but it wasn't very bad at that time.
I want replies from people who know what their talking about. Preferably mechanics in this field but if you know about cooling systems inside and out let me know what I should be looking for.
Thank you to everyone who can help out!
