I have a my95 WRX Wagon on which the radiator went kaput. I saw the temperature rising and stopped before it got close to maximum on the guage. nursed it to a filling station, making sure temp did not go above about 3/4. Tried putting some water in but it came out as quick as it was going in out of plastic edge of the rad. I replaced the rad and now the expansion tank is overflowing. I have looked into it with the engine running and some of the time it is bubbling and sometimes totally calm both at tickover and when holding about 3500 revs. I understand that bubbling is a sign of the head gasket gone but cannot understand why it is not bubbling all of the time. Can anyone tell me why please?

Many thanks

John F.

 

Any ideas?

 

could just be an airlock, not bled properly?

get a compression check done on cyclinders

sometimes it takes full operating temps to show a leak, once everything has expanded to its max size and full operating pressures.

if the gasket is blown across the into the cooling jacket -you can sometimes smell fuel from the air bubbles in the exp tank

 

Thanks for that. I'll try filling water through the turbo pipe.

Compression test cold and hot shows almost identical across all 4 cylinders.

I understand bubbling when the gasket has gone but couldn't work out how it doesn't do it all the time.
I haven't filled it through turbo pipe yet but earlier I warmed it up to check it and it bubbled then went calm, then I gradually increased revs to about 2500. Bubbles at first, then it went calm. I continued to increase revs to about 4000 and it stayed calm. When I released the throttle I got bubbles again for a couple of seconds then it went calm. I'm almost convinced it is the HG but the intermittent bubbles is confusing me.
Anyway, I'll do the slow fill through the turbo pipe and see if that makes any difference.
Thanks again.

 

are both top and bottom rad pipes the same temperature...if bottom is cold its still air locked

 

a few bubbles in the overflow are not always indicative of a gasket failure.
most obvious headgasket symtom is when it chucks all the water out of the overflow on boost and then overheats.
mine bubbles in the overflow tank now and then and its been like that since ive had the car. touch wood no problems. just a bit of localised boiling in the system i think.

 

Thanks for that guys.
Hoses are all hot.
Everything checks out OK except the bubbles. Sometimes water is blown out through the overflow indicating the head gasket. I would really like to understand why sometimes it bubbles and sometimes not.
I don't know if this has any significance but the header tank is the metal one from a later version and it is on spacers raising it about 20mm to clear the pipes etc underneath it.

 

Update
Yesterday I warmed the engine up then pulled the plugs one at a time and ran the engine on 3 to see which cylinder, when under pressure, was producing the bubbles. Guess what, I was getting bubbles every time. This confused me as I expected to find no bubbles at all from the faulty cylinder.
Does anyone know if it is possible for exhaust fumes to get into the water from the turbo as this is the only other way I can think of that pressure/gasses can get into the cooling system (or any other alternatives)?
Many thanks

 

have you tried running it on the road with the new rad yet? does it over heat still?
have you filled the system slowley to rid all air locks? if its not overheating then there might not be a problem as such. like i said mine did this and yet touch wood its still running like a goodun 18months on.