I own a 2006 Impreza Sti.

A few weeks back, the seal on my standard radiator went - coolant everywhere.

I replaced it with a japspeed aluminium one, wasn't a great fit, but it's in there.

When driving to a friends, to fit my coilovers, the top supply hose came into contact with the fan and sliced it open - coolant everywhere.

Got a Japspeed hose kit on monday and just fitted the said hose that was sliced open - after cutting it down to ensure it didn't hit the fan and was still clear of the belt.

The car drove fine, holding just below mid temp. like it did after initially fitting the new rad.

However, every time I put my foot down or hit boost, the temperature goes all the way up to red.

I've burped the system a few times, in hopes it was just that. But when the temperature goes of the charts, coolant literally bubbles out the bleed hose (small hose coming out the side of the rad cap) leading my to believe I'm getting air where I shouldn't be. - Worth noting, that there is no white in my oil, but my coolant fill, is a bit gammy.

Have I done a head gasket?

If so..

Who is the best place to go to in/ around Herts?

Should I change both of them at the same time?

How much poorer am I looking to be? (Numbers varying from £700 to £2000! scare me)

 

My headgasket went on my 07 STI about a year ago. Mine would only over heat and I would also get a surging noise from the water system with it eventually blowing through the water expansion tank.. I questioned on here about it and was told headgasket.. Apparently these types of engines don't get the traditional signs/symptoms of headgasket failure (oil/water mix) had it in garage an it was confined that the headgasket had failed.. Very common on this 2.5 engine. Had a couple of quotes and the cheapest. Drive in- drive out headgasket replacement was around £1500 (iirc!) so I decided to go fully forged..

Just to add.. NO garage 'should' not just do the headgasket...they should also do the bearings aswell.

Good luck

 

You might be lucky, get a sniff test done immediately to diagnose. Fingers crossed.

Meanwhile, you need to know there's no known way to bleed the Scoob coolant system once airlocked.
You need to start again, drain it, and then do a search on here for "how to" refill without airlocking.

Or ask if you don't find it: I've posted it a few times.

 

My previous 06 Sti would only leak on boost under normal driving it would be fine.
Only symptoms I had were air bubbles in the expansion tank after a hard drive and water noise from behind the dash due to a air lock in the cooling system.

Yours symptoms also sound like a hg problem.
Get a hydrocarbon test done to be sure.