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Cabin heating system blowing cold air..?


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Hi All, 

I really need some advice?!

I have a 2006 Impreza STi. The cabin heater is blowing cold air, which is a nightmare bearing in mind that it's rained every day for the last 18,000 days...

I have burped the radiator, thrice, by running the engine with the rad cap off and topping up with coolant. After I do this the heating works and blows hot air, for a short period then goes back to cold. 

There was a tiny amount of gunk on the rad cap and a tiny amount of oily type gunk that floated out of the rad, which could indicate a head gasket issue, however, the car is not burning oil and the oil does not have any impurities. And the head gasket was changed 4 years ago... And the coolant has been clear and free from gunk since..

Any advice?

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Scoobies tend to push combustion gasses into the coolant if a headgasket goes,i don't think I've ever seen one mix coolant and oil before (like most other engines do )

The usual sign is after using boost the coolant will bubble and spit out of the expansion bottle,  due to combustion gasses squeezing past the h.g and  pressurising the coolant system. 

When you burp the coolant and it works ok do you have to top up the coolant or just burp it ?

If you have to top it up evertime , it's either burning or leaking coolant . So check for tell tale "furry coolant coloured " bits around the coolant system in the bay (to indicate leaking) 

Or whip the spark plugs out and check their colour , as you should be able to tell if its excessively burning coolant by their colour too .

Failing that get a garage to do a sniff test for combustion gasses in the coolant.  If theres some in there its definitely a headgasket issue unfortunately 


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