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Possible head gasket problem my06 forester xten


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Hi can anyone recomend a good indi to do the headgaskets in the nottinghamshire area.

This is a strange one not losing any water no steam coming out of exaust neither any water no oil floating in coolant pipes do not get preasurised.I had a kind of missfire when going into boost thought it might of been down to the plugs as there was a brand new set of ngk's left in the car from previous owner took it to a garage got the plugs changed but befor they installed them had a compression test

cykinder 1 was 168 cylinder 2 was 158 cylinder 3 was 155 and 4 was 151 had a leak down test too all seemed ok also had a sniff test done never changed colour.the plugs that was taken out was brand new all looked like they was ok no signs of odd colour i did not realise it had its 90k service from subaru dealer at 118K miles in feb this year its had new water pump cam belt pulleys new rad there is some eyewatering bills with this fozzy its got 120k on now its never over heated but on two occassions the temp has started to creep up over half way and i have the torque app on my phone so i can see exact temps i have pulled over befor it gets to boiling point pulled up the bonnet and notice the over flow bottle half full no bubbles,Once it's cooled down a bit it has taken the water back to the rad i can then continue on without any further problems it doesn't throw a engine check light at all the only thing that as been done to the car is a prodrive exaust put on and maybe a mapping not sure could of just been a flashed one its been on a dyno its at 230.1 bhp at nearly 17psi boost which seems high for the standard bhp figure i cannot ask the previous owner he sadly as passed away so not sure if it's had the headgaskets done in it's life time like i say it does not throw any engine light but does have a slight hesitation goin on to boost there are no strange smells either coming in the cab starts on the button.

very strange one.

so thought i may as well get them done its a cracking motor with  all the goodies too.

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Have you checked the expansion bottle from cold ?

Should be half full and when hot should be ober the top line, do yiu get warm air out of the vents, if everythings fine I wouldn't pull the heads apart just yet as it's an engine out job at some places. Maybe it's an airlock, they are notoriously hard to bleed properly.

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Hi yes checked it from cold its at the second mark then when its been running it comes up to the half way then once cold it goes back to its second mark its definitely not losing no water there's not one bit of steam from cold start up no water around the exaust it's not using no oil at all done all the usual stuff to check if there's an airlock heater gets nice and hot fans kick in when they should and they are not constantly on and off it does have a slight fuel antifreeze coolant smell in the overflow,I was told one of the headgaskets could be lifting a bit under boost thats why i get a miss fire,well that's what it feels like when you hit boost but surely it would throw a cel its doin my head in lol and if it was headgasket i am sure the problem would get worse.If it is the gaskets i have been told it's a full engine re build it's no good just having the gaskets changed sounds like a big bill is on its way. :o

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Its not a full engine rebuild & from your remarks from tests likely not head gasket thus far.

Best get it checked thoroughly by decent subaru knowledgeable independent & take it from there.

Cooling system needs a good check with basics such as thermostat looked at/replaced & rad cap too, I would get it on rolling road to simulate issues & log all data & do sniff test on cooling too while on rollers to try pinpoint issue.

Your pressure test readings are not the best but certainly would want do more tests & inspect other areas prior to even thinking about head gaskets seriously.

A lot of misfire/hesitation issues when on boost comes down to ignition faults, fuelling, leaking inlet piping & crappy dump valves.

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Mr B thanks for your reply i will be changing the coolant this weekend replacing the thermostat too even though alll this was done in february according to cambridge subaru dealer they told me it came in with a overheating problem due to the rad leaking so whilst doing the service they changed the pump put new rad on did the cambelt and pulley change and did all the other stuff under the 90k service i will also change the rad cap and the expansion one too.

The compression test was done cold which i am not sure wether it would of been a better test when warm on the leak down test could not hear any air escaping only on cylinder 2 a slight noise coming from oil filler neck but once tdc had been reached it was quiet as a mouse it held all its pressure on all cylinders.

On the rolling road the chart showed the missfire when it hit boost the boost pressure held a smooth line all the way he told me it could be a coil pack going bad but would not know which one until it threw a cel which it did not do on the dyno,The engine never put out one bit of smoke neither any mist of water vapour at all under boost so the theory of the head lifting a bit under pressure kind of ruled that out for me anyways at least.And the thought of buying a full set of coil packs would be an expensive buy as all i keep hearing is these very rarely go wrong and it would be labour intensive to get one and go through them that way and being told there is no other way of testing them, its also been on a run and data logged nothing showed up?.

It is very frustrating to say the least but will go through it all again just to make sure and check for air locks.


It was from a reputable subaru indi that told me that it would need a re build its no good just replacing the gaskets i could understand that if water had entered the oil ,i suppose looking at it yes may as well have a rebuild then its taking the engine back to new state but still an expensive job.

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Most important thing with headgaskets is using quality gaskets & surface finishing on head & block, certainly things such as bore condition, rings, valves etc will be reviewed during the process but if engine otherwise healthy it now way a rebuild.

The specific issue on Subarus & head gaskets is mainly due lo more permanent contact of oil, petroleum & water on the gasket due to boxer design mixed with less than perfect head gasket design/material.

Your boost is 1.2Bar which indeed is high & do need be sure the fuelling & ignition is supporting this.

I would like see fueling figures from a power run & also ignition timing/knock, retarded ignition will cause overheating, would expect some CEL activity though.

Hard call with the results you posted to date. Compression test readings are not low but difference is out of tolerance spec but all over 150 is very good.

Would really expect pick up combustion gas with sniff test (gas analyser rather than chemical after running car till shows overheating ) or at least have some water loss if head gasket.

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The engine is in tip top shape as far as i can tell and thinking about it it may be down to the mapping i do not know who did it, the mods that have been done is the pro drive exaust put on and one cat removed there is no blow off valve or any other mod that can be seen,it could well be down to timing it may of had a bigger intercooler on it and taken off and just the exaust left on i don't know,? they did a sniff test with the emissions tester held over the overflow bottle and rad it did not move he had to put it near the exaust to check it was working it is a strange one i have put up the dyno runs so you can have a look see what you think.







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