syke

Hi guys,
I have some trouble with my car overheating when driven hard and I hope someone has an idea of what to do.

About 2 years ago the standard radiator on my v3 sti ra broke and the garage replaced it with a standard wrx rad (I was told they were the same).

Now, the car works perfectly when driven normally, but whenever I drive it on a track or on the ice it starts to overheat.

Most of the parts are checked by the garage (thermostat, pump etc.) and everything seems to be in order.

Any ideas of what to check / do?

TonyBurns

iTrader: (3)

Ok, from the top

Low fluid level
Bad circulation due to obstruction
Air in the system
Faulty expansion cap (leaking)
Heater matix failing
Head gasket failing

Start with those

Tony

syke

Thanks, though the garage has checked all the "normal" stuff such as fluid level, circulation, air pockets, expansion cap. Dunno about the heater matix (?) and head gaskets though. Would the car work normally if those were broken when not on the track?

mr_D

iTrader: (12)

most likely cause if its when under load could be stretched head bolts ! which in turn could mean your loosing water and then over heating.

Tidgy

is it dropping water? whats the oil temps doing?

syke

Haven't seen it dropping water but a lot of water comes out of the pipe in the front and to the right (the expansion "box"). The oil temp tend to move up before the water temp goes up.

I usually have to fill up quite a lot of fluid after a day of hard driving with some overheating.

mr_D

iTrader: (12)

headgasket faliure. for sure. just replcing mine now. stop driving it and start getting it done now before it over heats again

joz8968

iTrader: (13)

+1

I experienced the same symptoms (SMR engine ). I'm 90% certian lol it's the HG...

But BEFORE condemning, you could try dropping the coolant and refilling again by the "correct method" so as to burp/purge the system of any air, thus ruling out any possible airlock issue. Don't cost anything to carry out.

syke

HG failure even though it works perfectly when driven normally? I have to drive it quite hard to get it to over heat..

joz8968

iTrader: (13)

Yes, classic symptoms (exactly what I experienced too)...

What happens is the HG can suffer a tiny micro-fracture (esp. the WRX-spec fibre ones) which remains intact when NOT on boost (the normal <= atmos pressure isn't enough to disturb it). This is why a "sniffer test" at idle doesn''t necessarily prove a positive.

But as soon as you put meaningful boost pressure through the motor then this causes the HG fracture to open, or lift, thus pressurised combustion gasses getting into the coolant system and invariably creating airlocks. I bet after this happens, your bottom hose is stone cold, right?

syke

Haven't checked the bottom hose when it's over heating actually.

Damn, I was hoping for another answer more in the line of "flip that **** and push that button and it'll be all fine and dandy"

joz8968

iTrader: (13)

If only, eh...?

andyxros

they cheaked thermostat??? only way to cheak that is to remove and put it in pan water and heat it up and with a digital thermometer see what temp it opens at and if it in fact fully opens but that time they might as well of put a new one in i know its a biut diffrent but story on my layland DAF truck once was it was fine untill 10 mins pulling it up saddleworth on the m62 then all lights warning buzzers the lot and over heated turned out to be stat not opening fully and 2 degres over the threashhold,,,i just took it out compleatly seen as truck only used in summer,, first thing i would of done is re place it even if it worked or not after all the effort of timing belt off etc etc

mr_D

iTrader: (12)

+1

i was experiencing the same problems. i checked everything. a block test (sniffer) didnt come back conclusive. worked once and not the other 2 times i tried. i had the same symptoms. drained all water and refilled. still the same. bought a new pressure cap and that didnt sort it. found out for sure on the rolling road as i got to watch what happened then,

i have stripped it down and checked it. putting back together tomorrow hopefully.

i had to have my heads skimmed 8thou and i took the oportunity to fit new cometic 1.6mm headgaskets. and new studs.

you have to be careful because the head studs/bolts could of stretched. which caused the cooling system to pressurise. this then caused you to loose water and over heat and then gave you headgasket failure.

its not good mate and i know how it feels. i have been lucky enough to do all the work myself so saved alot of money. but if you search around and buy all the parts your self you might save some money.

RS74

Had same prob on my 06 wrx.. normal driving ok hard driving coolant level rising up over reserve tank and overheating. did thermostat and block test all come out fine ...

but block test does'nt always show up as i found out .
whats happening is under load the headgaskets are failing, mine had problem for about eight months and i kept on thinking it can't be gaskets cause it would over heat on normal driving but no when gaskets taken out you could see where they'd gone

i put cometic ones back in as there stronger..
get it done mate prob cost you just short of £1000

sorry mate but if you leave it your only going to cause more damage

syke

Thanks for the replies guys, I guess I'll have to make the call to the local subaru garage and have them change the HG. I guess they'll be taking the engine out - so except for changing the head studs / bolts and the HG is there something else that's good to do at the same time while the engine is out?

/Regards Stefan

joz8968

iTrader: (13)

Cambelt/tensioners - inspect/replace as necessary.
New thermostat and/or water pump.