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It's my first post on here, was wondering if anyone had any thoughts or ideas on best steps to take with the situation I'm in.

I have a 59' reg (2010) Outback with the 3.6 EZ36 engine and I live in Aviemore, Scotland. I bought the car a couple of years back with 67k miles, 5k later the coolant light began to illuminate intermittently, this got worse to the point where it was flashing (indicating to pull over let the engine cool). The local garage carried out a pressure test, which came back fine, I proceeded to take it to the Dealer in Inverness who told me it's likely that the head gasket has gone; the dealer's initial price estimate for HG replacement is roughly £4000!

I've yet to enquire with the local garage to see if they're able to do this, yet alone come up with a price estimate (they had to order a pressure testing kit for their initial check).

I'm thinking I ought to try some liquid Head Gasket Sealer to see if that works first, but assuming it doesn't work and the local garage can't do the job, I'll be left to decide whether I get rid of the car or stick £000s into it (I originally bought it for £13k)

Just for context, the journey from Inverness back into Aviemore has left me feeling uncomfortable driving any distant more than a few miles at a time due to having to pull over so often to let the engine cool, so I'll probably have to organise transport for the car to take it anywhere in the future.

If anyone can recommend a Subaru/Japanese Car specialist that's not too far away it would be greatly appreciated; also if anyone has any experience with these or other Subaru engines with HG issues any advice would also be terrific 🙂



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H6s are not unduly prone to HG failure but if it's overheated, all bets are off. Firstly, when you first got the coolant light did you check the levels in the radiator and the expansion tank?

Has the temperature gauge risen at all indicating overheating? These engines normally run with the temp indicator steady at 9:00 on the gauge. Does it push coolant into the expansion when warm/hot and if so does it draw back when the engine cools?  Pressure tests can be ambiguous as are combustion gas/coolant tests. There is usually no mixing of oil/coolant. History of the car? It could be as simple as not properly burped or the wrong thermostat, Subarus are fussy about using genuine Subaru stats.

If it ends up being the HG, very complicated to do so £4000 is possible.

I wouldn't use HG sealant (Holts Radweld or similar) unless you are really desperate and don't mind small coolant passages getting gummed up with crud.

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Yes H6 headgasket not a common issue .
It needs looking at by decent specialist and that not a dealer generally lol .

I generally sniff test the cooling system, chemical test can be useful too .

Really needs a thorough diagnosis, check actual power/grounds on temop sensor and sensor out values are true, thermostat fans and general coolant system condition/flow and pump needs be reviewed .
Removing plugs and visual examination and a endoscope can find useful results as can a good operator of a leak down tester, checking the bottom joint of head gasket can be useful too .
Is an engine out job do the heads, while engine quick to remove is lot of hours in a good job and quality parts and machine shop don't come cheap.
My quick pricing on head gaskets without reviewing it be 2.5K but could go to 3K .
My first thoughts would be it lower chance of heads so couple hours or leaving it with mechanic for few days for good diagnosis/ use testing is where you need start .
A garage that doesn't even own a pressure tester is not a good place start nor is a dealer who says 4K for head gaskets without advising you on thorough diagnosis, you need experience with test gear be any real good with it and for you get value from the repair you going ideally want a garage who done a few subaru engine builds as you don't want them learning at your cost .

Make effort find good independent garage and only commit to gaskets if reasonable evidence found from proper testing not guessing .

Good luck ...

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  • 2 weeks later...

Thanks guys - really appreciate the feedback.

Oddly, my H6 Outback doesn't have a temperature gauge - just a light which come on (or flashes) when getting too hot. It has pushed coolant into the expansion - and it's bubbled over when too hot. I think the main take-away is that I need a decent reliable specialist/mechanic who will take a proper look and diagnosis (endoscope etc.) - and experienced in Subaru engines. I'll have to do some research on where to go..... 

Will keep you posted!

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If you know how to remove the thermostat, cut the internal out with pliers and stick it back in and see what happens.

Or before you cut it try and boiling the kettle and pour boiling water over it in a cup and see if it actually opens.

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  • 1 month later...

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