Over the last couple of weeks i've noticed the level in the header tank drops to the bottom of the header tank
After running on constant (standard boost) the coolant decides it doesn't want to stay in the system and pisses out of the top of the header tank.
The cap had some of it's tabs bent so it would grip the top of the tank properly but this morning did it again.

The car is a 93wrx and has the standard plastic tank and the cap has 'HKT radiator cap C-10 0.9kg/cm2 88kpa' written on it.
The car had the headgasket sniffer test and the result was negative.

So would it be a faulty cap (been on the car about 3 years) or the header tank (been on about the same time) being worn down as it's plastic if so are they any better header tanks to fit.
i'm going to the garage this afternoon to see what they can do.

 

The plastic tanks regularly fail around the seam where the metal clamps the top and the sides together. Usually though you'd be able to spot this easily. If the header tank or cap shows no sign of water leakage then check the usual places for leaks, radiator / hoses, thermostat etc.

 

It was definetely coming from the top as i parked up at work then saw the steam/coolant coming out of the vent area and gap between the wing and bonnet opened up the bonnet and the tank was a nice shade of coolant

I did see a very,very small bubbling bit of liquid underneath where the cap sits.

Do later model imprezas have better tanks and if so can they fit earlier cars?

cheers

 

you can buy an uprated cap from the likes of "sti" or zerosports rated to a higher setting, but if they push out coolant its 9/10 the headgaskets failing, but they only fail at the water jackets when under boost.

headgasket tests don't very often check the system while itys on boost which is why you never got a true reading

you could probably fit an uprated cap, and not lose as much coolant, but you will still get bubbles from the overflow tank as it will retain more pressure instead of just dumping it all at the first sign of pressure.

i have been doing the same on my car while collecting parts for the 2.5 engine swap, i fitted the uprated 1.3bar sti cap, and it means while i am not losing coolant, i do have bubbles fro the overflow tank as the uprated cap stops all the pressure from dumping out instantly, my head gaskets are failing !

 

Overflow tank that's the one by the battery isn't it and that doesn't fill up with coolant/water (or am i mistaken)?

 

Just buy one of these mate, the tank will fail at some point. Mine did but why risk further damage

https://www.scoobynet.com/essex-scoo...ml#post8071367

 

Very nice but £150!!!! ican see why it won't go but damn.

 

A new cap is only £20 try that first, and you would need it anyway if you went for a new tank.

 

stock cap fits with forge tanks

 

Yes but over time they can shrink/perish and when fitted to the forge not seal properly best to renew the lot imho

 

most likely as stickyMicky said head gasket starting to go