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Zero compression in cylinder 3 in 2008 Outback 2.5L wagon

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236k miles. Both heads rebuilt around 180k after we got it for cheap (tbelt break). Engine was replaced by previous owner, history not known. Sudden onset of running bad. May or may not have been some winter joyriding. Wondering about oil starvation? Runs very rough, engine is shaking, stalling at idle. cylinder misfire codes are not new. Able to limp home.

At the end look for the cam wobble

Tried a few quick fixes but no major improvement. The timing belt was off one tooth on the pass side cam. Reset the timing and runs better but still shaking, low power and still stalls randomly. Oil puddling on ground underneath on pass side from tbelt cover between oil pump and oil filter. Replaced the crank seal but probably also cam seal leak.

CEL flashing intermittently, probably misfires. New Diamond coil  (existing diamond coil didn't look bad at all). No improvement. Changed plug wires to new NGK (from existing NGK). New NGK plugs. FR5AP-11. A bit of chunky carbon on one plug (either 1 or 3) and #4 was loose possibly causing low compression and shaking.

Now running with naked timing belt so everything is visible. Able to turn the timing belt with a socket on the cam bolt, but it doesn't feel loose at all. Cam sprocket is wobbling while running. Cam oil seal is compromised and oil is puddling below the cam. Oil coating the belt and flinging around the engine bay. Is the cam itself out of round? This seems impossible. Maybe the cam journals are gouged out. Car is knocking. Bottom end problems?

Finally got the car on a trailer after sitting in a parking lot up in Michigan for a bit. Back in the garage. Just now checking compression after finding a new ride for the daughter, of course a Subaru.

Cylinder compression is good on 1, 2 and 4 (220, 205, 200) but ZERO on cyl 3. Plugs look ok, not oily.

Will pull the engine and check out the head. Probably the valves got grenaded on #3 or worse. Car hit a deer in 2024, needing a bunch of sheet metal replaced in the front. Tbelt cover was cracked. Wondering if the cam sprocket took an impact that was missed.

Edited by 89Ru

  • Author
21 hours ago, bushytails said:

Could be a broken cam between 1 and 3.

Could be given what I found. Got the cam sprocket off. The head of the cam itself has a wobble. The intake ports in the head were half full of fuel, valves are tight apparently and certainly not moving. No cylinder compression from lack of valve movement.

Edited by 89Ru

Sounds like a broken cam... Probably going to need a new head, since I can't imagine the journals are still good.

  • Author
7 hours ago, bushytails said:

Sounds like a broken cam... Probably going to need a new head, since I can't imagine the journals are still good.

Agree. Given the wobble at the sprocket side I'm pretty sure there is damage to the head.

  • Author

Cam is broken

The far end of the cam (non sprocket side) isn't seized, or at least it isn't now. Spins free, supported by the end and center journals. Probably seized at some point. Sprocket side journals are 'remodeled.' Will take apart the AVLS assembly and look at the oil ports.

top view passenger side head

broken cam

cam wear

cam fractured

non sprocket side cam journal

cam journal sprocket side

center cam journal

cam cap sprocket side

cam slot

Edited by 89Ru

It looks like the cam ran without oil until it seized, from how trashed the rear journal is... If I were you, I'd probably be looking for an engine, not just a head. Would be a shame to put a new head on and then find the bottom end looks the same.

  • Author
8 hours ago, bushytails said:

It looks like the cam ran without oil until it seized, from how trashed the rear journal is... If I were you, I'd probably be looking for an engine, not just a head. Would be a shame to put a new head on and then find the bottom end looks the same.

So the rear journal isn't good either. I would describe the front journal as trash where the cam had a definite wobble and the aluminum is creeping up the shaft.

The AVLS ports look ok, other than a bit of sediment in the filter screen. The engine was run low on oil at one point and had developed a slight knock at idle so I was leaning toward a JDM replacement anyway, but this clinches it. The oil pump was resealed at the previous head rebuild.

My bad, I think I got one of the pics backwards in my head, and thought the cam was totally ruined on both ends... the rear journal doesn't look totally ruined. There's still definitely some scoring visible on the cam in both the center and rear, though. But if it has a knock, it's time for an engine anyway.

Edited by bushytails

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