Hi I have a 2006 H6 OB which I'm fairly sure the head gasket is going. I've had the thermostat replaced with an OEM but I get overheating on loading like hills or speed. It will run just about ok round town and will idle forever without problems. However I'm getting a few bubbles in the overflow. It's done 186k but was hoping for more as I know its a fairly bomb proof unit. 

Has anybody had any luck with gasket sealers such as Steel Seal etc. ? It doesn't do big miles but I'd like to try and get some more life from it as it's a great car.

Any advice appreciated.

Thanks

I have only read bad things about liquid gasket sealant and the subaru product steer well clear - blocked coolant passage ways leading to engine destruction

OK thanks - doesn't sound good. I've heard drilling holes in the thermostat is also a temporary work around?! I'm not in the market for new engine or full repair just something to keep it on road.

On 9/8/2021 at 12:13 PM, markrw1 said:

OK thanks - doesn't sound good. I've heard drilling holes in the thermostat is also a temporary work around?! I'm not in the market for new engine or full repair just something to keep it on road.

I am not sure how drilling the thermostat will help as it already has a small hole to enable a little flow when closed and when heating up it will open fully so as soon as it gets warm you will have full flow to the radiator.  Is it possible you have and airlock in the system?

Have you ruled that the issue could be with the coolant side rather than engine? Is there any noticeable oil leaks or consumption? Is there a change in appearance to the engine oil on dip stick or cap?  If not maybe your coolant system is just gunked up and under increased load insufficient radiator coverage is available to maintain the desired temperature?

 

A coolant flush might be a good cheap place to start using a suitable cleaning product in the mix before draining.

Above post highlights what needs be done and that is diagnose the source of overheating .
H6 is not a common one for HG failure and it impossible to make best decisions on how improve situation until you pin down what actually root cause .
Don't guess, test . Is easy and cheap test with gas analyser with rad cap removed and from expansion tank, sounds like you can induce overheating so testing during overheating should be pretty easy achieve .