i've got a 06 wrx hawk eye.. for about a year the reserve tank when been for a 10 mile run or more fills with coolant . the engine never overheated. until this week ..
checked the bottom hose and found was cold .. replaced thermostat also replaced both rad caps. engine not yet over heated again but the reserve tank is filling and air bubbles coming out of pipe. pipes very very hot and the back pipe to header tank bubbling (feel it when touch vibrating with air) any ideas. hope not head gasket ... did do a block test about 2 months ago and seemed ok .. any help appreciated

 

Sniffer test isn't conclusive I'm afraid, and it does sound very much like a head gasket failure to me i'm afriad. Sorry fella - been there so I know how you feel, but if you take it to the right place you can get the job done for around £1000 all in.

 

cheers not what i wnted to hear but i thought that myself.. won't cost me that much as i run my own garage. just did't want to start stripping it down , but on the other hand good do some mods while the engine is out...



only seems to happen when been giving it some .. thinking when under boost the gaskets are failing , simalar fault with my mates 56 plate sti, changed his headgaskets and cured it. i am gutted

 

when you say it fills with coolant do you mean it raises the level a little or a lot or over flows it?
obviously its normal for the level to rise in the expansion tank and bubbles are not always indicative of head gasket failure, they can be caused due to localised boiling.

mines been bubbling for 18 months or more after a hard run.
i fitted a 1.1 bar rad cap to replace the 0.8 one and that helped.
i would have though if there was a gasket problem it would have over heated and finihed its self off after a whole year.

 

surely its not a problem until it starts to over heat? thats where i am with mine. then you can catch it early before it does any damage as you will be ready for it.

 

i think i'll keep a eye on it , i've only just changed the thermostat today as it over heated on friday . put the stat in kettle and it did'nt open till water boiling ,where it's spose to open at 78c. i might just have a bit of air in the system, fingers crossed , to answer the other question the water in the tank rises near to top on most occasions but somtimes after a hard run it over flows. had the car from new and it never did this until about 12 months ago.

 

most likely head gasket starting to go as the heads are just starting to lift under boost ..its will get worst, so fixed before in knackers the engine up.
but if you had its since new and not done any mods ..........it very strange though for a standard car to blown a head gasket ??

i had a forged 2.5 fitted and after running-in , the head gasket started to go , had all test done on the car with no sign of gasket failure but the signs are as you mention .
will only overheat at speed of 90mph+ on long run (6miles or more ) as the heads were lifting ever so slightly.

 

I'm having the same symptoms - but it took 18 months for it to really show up.
The overheating is from the rad picking up an airlock and stopping flow - hence the cold bottom pipe.
I bet you can take the rad cap off right now without loosing any water.
Did the new caps and thermostat but it never cured it.
No major overheating.
Expansion tank will gradually fill up as there's no suction back into the cooling system. A hard run will overflow it slowly, so I have been tipping the contents back to the header tank.

A rebuild is about to follow....

 

Butty are you saying the air lock in the rad is caused by air getting there from head gaskets or just air lock .

 

to aswer the other question the car is not standered , full decat , fuel pump, STI T.M.I.C .and remap running 280 BHP 355 LB'S TOURQUE. was thinking of vf43 turbo and another map so might put forge pistons in while doing headgaskets ...


thanks for all the advise , but think i'm going to take engine out and do gaskets anyway going to upgrade to steel ones instead of standered crap

 

mine were the multi layered sti metal gaskets ......its not the gaskets that at faults , it the rebuiling of the engine (ie torqueing the head bolts etc etc )

 

Its the gas getting through the HG that seems to collect there. You'll probably also hear a few bubbles going through the heater

 

run it over weekend and when driving normal temp gauge on normal, and level in reserve tank ok.........
when give it some boost and a hard drive the level in reserve tank rises and bubbles in tank. can also hear air in matrix under dash....
me thinks headgasket . no point in putting it off, i'll get it done and if it doe'snt cure it i'll head butt some walls . poss head lifting while under boost like you've said

 

I had a turbo change last week.

On the first big run since it was done (that night actually) I noticed the temp starting to rise - about 3/4. I sat off-boost all the way home (motorway) so good air flow managed to keep the temps just above normal.

Sat on the driveway in the dark for about 20 minutes with the fan on to bring the temps down.

Next morning - checked the coolant levels and they were just below low. Rang the tuner and he confirmed that there would be some coolant loss during a turbo change and that it had been topped up. I topped it back up and touch wood - it's not dropped below the top mark. No signs of anything bubbling over, all heaters working and have given it some hard driving since - the temp hasn't moved at all.

Think I've been lucky by catching it fast? Incidently, I have always had the "water gushing" noise at the back of the dash since owning it. I notice it a lot more now - is this an indication of an air bubble in the system? If so - how do you remove it?

 

Think I've been lucky by catching it fast? Incidently, I have always had the "water gushing" noise at the back of the dash since owning it. I notice it a lot more now - is this an indication of an air bubble in the system? If so - how do you remove it?[/quote]

remember reading on nosiac that if you havent enough antifreeze in the system you will hear that gurgling sound from the heater matrix

 

As I thought then - sounds like trapped air.

When the car cools down, going to go and top everything right up and run the system with the res lid off - see if I can get the bubbles out!

 

Engine coming out today.. thanks for all the info.