H6 EJ30 Head Gasket / Cooling Burping

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Tone
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H6 EZ30 Head Gasket / Cooling Burping

Post by Tone » Mon Dec 05, 2016 4:07 pm

Hi forum members...

So after 349,000 kms my H6 seemed to need head gaskets. From what I've read on various forums, this is usually common earlier that that. Anyway, after some research I decided to brave the task, pulled the engine and replaced the gaskets. I must say I'm so impressed with how little wear and tear was obvious on this engine!

Now, after a month or so of driving and about 1500kms, I'm still trying to figure out what is going on. Either I still have a cylinder - coolant leak, or there is some other weird way that air or some type of gas is getting into the cooling system. It's definately better than before the head gaskets were done, but still not 100%

Generally the car remains cool. At random times I can hear gurgling of some sort of gas in the heater core, and if I don't give it a good rev to clear the gas, then it seems the water pump cavitates and the temp spikes to about 2/3rds. If it does, a quick rev to clear to gas bubble pulls it straight back down again.

The water level is going down ever so slightly. It doesn't seem to be pushing water out the overflow bottle (no obvious coolant stains). And I can't see any leaks.

I've been trying to spot some sort of trend or clues to help solve it and so far, nothing.

Any ideas would be very much appreciated.

Thanks,

Tony
Self Confessed All Wheel Drive Addict. Been Driving Subaru's for many years. Not sure why I went astray and had an Audi Quattro for a year. Came to my senses and got myself another trusty Subaru Wagon!

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Jeff
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Post by Jeff » Mon Dec 05, 2016 6:37 pm

Put a H block in the heater hoses

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El_Freddo
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Post by El_Freddo » Tue Dec 06, 2016 5:11 pm

What sort of runs does you H6 do in that 1500km - long highway k's or short runs around town?

I'm only asking as the EJ's can be difficult to properly bleed if not taken on a big run. I'm sure this would be the same for the EZ's.

To me it sounds like an air lock in the heater core. I know the L series used to make gurgling sounds if you put the heater hoses back on the wrong way.

Subaru engines are well built from factory and if serviced regularly they will keep going and going. Over 300k km for a head gasket is really good.

Also, did you get the heads checked to ensure they were flat? If overheated they can warp and replacing head gaskets sometimes isn't the solution to solving the problem.

I hope this is not the case!

Cheers

Bennie
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Tone
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Post by Tone » Tue Dec 06, 2016 6:56 pm

Thanks Jeff and El Fredo,

Jeff, I'm intrigued by the idea of the h-block. How will that solve the issue if there is a mystery leak or blown gasket?

El Fredo, I agree how well built this thing is. There was almost no wear evident on the cylinders or cams, and very minimal wear on the timing chain guides, so little that I didn't think it was worth replacing. There was also hardly any carbon on the heads, a little more on one side, I suspect because I have a dodgy o2 sensor on one bank. Unbelievable condition for 350,000kms!

Heads were tested, machined and fully serviced, they reseated and reshimmed all the valves, which is probably why it's running like an absolute champion at the moment.

Also did new water pump when everything was apart.

It's my work car, I'm a contractor/installer so I do a lot of short trips plus also some long ones. It's actually done 2500 kms (1500 was a guess, which proved very wrong when I checked today) which includes a few 75km trips. I've also done all manner of things to try to burp it. It can sometimes go a whole day or longer trip without making any gurgling, then will start again next day!

Unfortunately the only thing I can think of is that not replacing the bolts, or a spike in temp I had soon after re-assembly due to a hose that wasn't secured properly has resulted in another head gasket leak. I also didn't have the deck machined or tested for flatness. I'm desperately hoping to find something else.

Car is going well enough to do a lot of KM's the way it is though, just need to keep a bit of an eye on temp and give it a rev if it goes up a little.
Self Confessed All Wheel Drive Addict. Been Driving Subaru's for many years. Not sure why I went astray and had an Audi Quattro for a year. Came to my senses and got myself another trusty Subaru Wagon!

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Donkeytits1
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Post by Donkeytits1 » Wed Dec 07, 2016 9:26 pm

Any oily gunk get into the cooling system?

I cooked my EJ22 and caused a small head gasket leak between the cylinder and water jacket. Symptoms were just as you describe. Running good, then get all hot and go stone cold again. Took a while before I figured out that it was caused by this greasy gunk that was building up in my cooling system that was caused by the head gasket leak - There wasn't much build up of air, just this oily black gunk

After fixing the gasket and cleaning the cooling system, non issue.

The problem works like this: Subarus are strange in that they are reverse flow, meaning the thermostat is in the bottom and to open it relies on a small coolant bleed circuit to pass hot water from the top of the motor to the wax pellet of the thermostat at the bottom so it can react. In most other cars the thermostat is on the hot side, so the hot coolant just flows straight through it. This bleed circuit includes the heater core, which for reference is a pretty fine pitch and easy to clog.

If you've had greasy blow by sent into your cooling system, it can coagulate in the heater core like it did in mine. This will impede the flow of coolant to the point where the thermostat will not open until the reduced amount of bleed circuit flow is hot enough to open the thermostat or sheer conduction heats it up enough. Then coolant flows for a while, and temp lowers. Keep in mind he temp sender is at the top of the engine, so it is basically measuring the bleed circuit temp.

Basically to clean stuff I poured in and soaked my heater core, radiator and hoses with turps, then flushed it out with degreaser, then water, then soapy water then water. And rebuilt the entire engine, which included a cooling jacket degrease by default. No problems since.

I wouldn't worry about the bubble noise - on its own. Our Gen 1 lib has done that forever. I remember it as kid even when it was a new car because mum would always comment wondering what it was and if she was ever going to get damp feet haha. A small bubble isn't going to ever stall the pump or collect in the thermostat.

Sweet job doing the head gasket on an EZ. How was it torquing up the 60 bolts on the chain cover? :P Cool to hear it was pretty fresh after 300k aswell. My project engine has 180k on it, glad to know its a baby

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Donkeytits1
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Post by Donkeytits1 » Wed Dec 07, 2016 9:42 pm

Also a thought, unless you have unfortunately still got head gasket problems, the only other way to consume coolant without it leaking is to vent it as a gas. Which could be happening if you're getting hot regularly and venting hot water and a bit of steam into the overflow tank.

Or, a slow leak inside the car, but surely you'd smell that.

Oh, just remembered how I determined I had a clogged heater core; I just bi passed the heater core with a piece of hose and the problem went away. And by deduction, for me the only source of that gunk was a head gasket or some other engine-coolant jacket seal.

So thats what Jeff is basically suggesting with the H block - Bridge the two hoses so some water can flow around the heater core. You'll notice lower heater performance though.

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El_Freddo
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Post by El_Freddo » Thu Dec 08, 2016 11:27 pm

Further to what DT said above: the thermostat is mounted correctly so the side that requires heat to open the thermostat is on the hot side of the engine - as in cooled coolant will enter the engine's cooling channels when the thermostat opens. The whole system is effectively upside down.

While the heater core circuit is the one that heats then opens the thermostat, I've had my heater core (and block, radiator etc) frozen. The engine, after a process, ran at proper temp even while the heater core was still frozen. I knew it was frozen as my heater was blowing cold air and my auxiliary mechanical temp sensor didn't move for ages while the heater lines were "crunchy" to squeeze - and it's tapped into one of these heater lines. I've not needed to do the H block trick yet.

I'd be monitoring your coolant levels and install an engine watchdog (about $150 on fleabay) for piece of mind - it uses metal temp rather than coolant temp.

Cheers

Bennie
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