Coolant overflow on track days

[Fatt_Mitz]

Hi all, first post...

I'm having trouble with with my STI when using it hard on track. I should first point out that there is absolutely nothing wrong with the car in normal day to day use!

When its having a thrashing coolant overflows into the expansion tank (as expected) but then starts to overflow all over the engine bay While doing this the temperature stays normal on the gauge

When I pit in to cool the car down the temperature at idle starts to rise, most of the water in the expansion tank is sucked back in by this point.

Does anybody know what the crack with this is? Could it be dodgy radiator cap? Will upgrading to 1.3 bar caps fix this? If so do I get 2 caps (1 for the radiator and 1 for the pot next to the turbo)?

PLEASE HELP

[stiimpreza1984]

Bubbles in Coolant I have a similar problem but no overheating or any other issues just blows bubbles out the overflow expansion bottle when reving the engine lightly on idling, upgrading my cap to 1.3 bar cap shorlty so thinking this will cure it and must change rad to as leaking a tiny tiny bit

[Fatt_Mitz]

I'm not convinced, there seems to be a lot of inconsistency regarding rad caps. If you look at some of the Impreza race cars they seem to be running 1.1bar caps, others have one 1.3 bar cap and some have 2???

Surely the pressure in the cooling system is the same all the way through?

In which case putting on a single uprated cap wont solve the problem, it will just make the pressure relieve from the 1.1 bar cap.

What do you think?

[stiimpreza1984]

Rad Cap Ratings also how old is the waterpump and the thermostat but dont think these are your problem really?

[Fatt_Mitz]

Yeah I saw that thread but it doesn't really help to be honest. I think the water pump and stat are the originals (car is 2006 with less than 20k). The car warms up without any issues, and stays cool under road conditions, its only when I give it the beans on track that it complains.

Also I'm fairly sure its not the head gasket because it made 351bhp last week on the rollers. It wouldn't be so high if there were compression issues.

It might be the bubbling issue you been talking about or a failed rad cap. Is there any way of bleeding the air other than taking the caps off and running the engine up?

[stiimpreza1984]

Originally Posted by Fatt_Mitz

Yeah I saw that thread but it doesn't really help to be honest. I think the water pump and stat are the originals (car is 2006 with less than 20k). The car warms up without any issues, and stays cool under road conditions, its only when I give it the beans on track that it complains.

Also I'm fairly sure its not the head gasket because it made 351bhp last week on the rollers. It wouldn't be so high if there were compression issues.

It might be the bubbling issue you been talking about or a failed rad cap. Is there any way of bleeding the air other than taking the caps off and running the engine up?

Know what you mean you think the bhp be down a lot more if it had compression issues, could just try the rad cap like..... always bled it with rad cap off but dont know of any other way apart from the way to bleed system from the manual here it is:
WARNING:
The radiator is of the pressurized type. Do not
attempt to open the radiator cap immediately
after the engine has been stopped. Wait till engine cold.
1) Lift up the vehicle.
2) Remove the under cover.
3) Place a container under drain pipe.
4) Loosen and remove the drain plug to drain engine
coolant into the container.
5) For quick draining, open the radiator cap.
CAUTION:
Be careful not to spill coolant on the floor.
6) Drain the coolant from reservoir tank.
7) Tighten the radiator drain screw securely after
draining coolant.
8) Slowly pour the prepared coolant from radiator
filler port to neck of filler, then pour into the reservoir
tank up to “FULL” level.
Coolant capacity (fill up to “FULL” level)
Non-turbo AT model:
Approx. 6.9 Litres (7.3 US qt, 6.1 Imp qt)
Non-turbo MT model:
Approx. 7.0 Litres (7.4 US qf, 6.2 Imp qt)
Turbo AT model:
Approx. 7.6 Litres (8.0 US qt, 6.7 Imp qt)
Turbo MT model:
Approx. 7.7 Litres (8.1 US qt, 6.8 Imp qt)
9) Securely install the radiator cap.
10) Run engine for more than five minutes at 2,000
to 3,000 rpm. (Run engine until radiator becomes
hot in order to purge air trapped in cooling system.)
11) Stop the engine and wait until coolant temperature
lowers. Then open the radiator cap to check
coolant level and add coolant up to radiator filler
neck. Next, add coolant into reservoir tank up to
“FULL” level.
12) After adding coolant, securely then install radiator
and reservoir tank caps.

[Fatt_Mitz]

Ok thanks for that, I will get hold of the uprated caps and try to bleed as per your procedure. Thanks again for your help, I have another track day in 5 weeks so will let you know how it goes.

[stiimpreza1984]

Cheers would be interested how it goes

[Fatt_Mitz]

Regarding the 2 cap dilemma... the standard cap on the radiator is rated at 1.37 bar where as the one on the plastic pot next to the inlet manifold is rated at 1.08 bar. This is the one where the fluid will leave for the expansion tank when it gets super hot.

I have ordered one of these, will let you know if it fixes the problem.

[stiimpreza1984]

Did you sort the problem fella?

[Fatt_Mitz]

Hi, sorry I haven't been in touch sooner. The trackday was a nightmare, amongst many other things the overheating problem remains!

The high pressure water cap didn't make an ounce of difference. Although I did pay more attention to the temp gauge this time. Seems to overheat when I'm on a cool down lap after a thrashing, when the air flow to the rad is less.

also with the heaters on flat out there was no warm air. I tried to bleed the system a few times but to no avail, I fear the worst... head gaskets!

Its booked into my local dealer this week so will post reply with their findings.

[stiimpreza1984]

Originally Posted by Fatt_Mitz

Its booked into my local dealer this week so will post reply with their findings.

Best of luck with it

[Tidgy]

do you know what your oil temp is doing?