Quickest possible question regarding 2001 3.0 H6

[jonathan909]

Interference or non?

[el_freddo]

I’ll put my bet in for interference. But chain timing rather than rubber belt cam timing, so something needs to be pretty catastrophic for valves to hit pistons in this engine - anything is possible though!

[jonathan909]

Hoping for a known fact rather than a bet.

[el_freddo]

True. On the flip side I’d rather a known fact that it’s NON-interference than a bet that it is. 

I’m 99% sure the last non interference engine Subaru produced was the gen1 EJ22E. The Gen2 EJ22E used roller rockers that helped bump the compression ratio for better power but the downside was the engine became an interference engine. 

Since the H6 is chain driven, interference or non-interference shouldn’t be an issue unless you’re trying to settle a pissing competition between you and a mate. 

Edited 1 hour ago by el_freddo

[jonathan909]

No, this is a real-world problem.  Car died very suddenly on the highway (en route home from the glass shop with a brand-new windshield after a windstorm+tree took it out.  Such is my life these days.) and the symptoms are:  Cranks, but sounds different, like less stuff than normal is turning; cam position sensor error.  That it's turning at all seems like somewhat good news, as that suggests I don't have a piston wedged against a valve, though it doesn't mean there wasn't a hit.  Hence the question.

So my first guess is a thrown chain (the EZ30 has two).  But since then (last week), winter has set in here for real - it's subzero, we're under a foot of snow, and the car is not (yet) in my (unheated) garage, where I'll have to pull the 64-bolt timing cover in order to confirm my suspicion.  And first I've gotta bolt a winch onto the far garage wall so I can pull it in...

 

[el_freddo]

How many miles on it? And what’s the service interval for the timing chain? 

Easiest way to determine whether your suspicions are on the right track is to do a compression test. If there’s a cam timing issue I’d expect one bank to be far lower than the other. 

If a chain let go, I’d expect some sort of grinding/crunching noise of the broken chain and spinning components when cranking the engine over. 

If the chain is intact, it could be a tensioner let the timing chain skip some teeth. 

Either way, if this is the issue, I see some very un fun times ahead. 

Last thought: check the cam sensor and rule out that there are any issues there. Cam timing sensor is used for spark and injector pulses from my understanding. This could change the engine tone/noise when trying to start. 

All the best

[Numbchux]

I have not seen anything officially saying one way or the other. But I would also bet interference. Even the 2.2 went interference in '97ish. That said, I see the FSM has a specific note to use caution installing the timing belt on a 2.5, as incorrect timing could cause piston to valve contact, and there is no such note in the 3.0 timing chain section....

I don't think I've seen or known of one break a chain. I've heard timing chain noise several times before due to damaged/worn guides and/or tensioners. Not that it isn't possible, but I'd be highly skeptical that it just broke without making a bunch of noise.

What Cam sensor code? P0340 is for cam sensor circuit, indicating a wiring issue or failed sensor, P0341 indicates good signal but out of time. I've had engines attempting to start with bad sensor data sound strange while cranking.

 

If it broke on the highway, the valves are already bent. It'll turn over nicely now.

Before you touch those cover bolts, definitely do a compression test. If it fails that, I would drop the exhaust and look up the ports at the valves you can see (IIRC the front valves are hard to see through the single exhaust ports), and then crank it again to see if you can hear the compression blowing out the exhaust.

If you have cylinders with no compression, but the offending valve cover and check to see if the buckets move freely and smoothly. While a stuck valve won't prevent a bucket from moving all the way out, there won't be any spring pressure on it.

I believe you can see the bank 2 chain through the oil filler cap.

Drop the oil into a clean pan and look for debris. Cut open the filter for the same. I would expect to see considerable metal in the oil if the chain has been failing. Maybe even drop the lower pan and look for bigger pieces of debris.

 

I have an 01 H6 with no compression on cylinder 3. It all blows out the exhaust. I removed the valve cover and can move the valve buckets/springs freely with a prybar, resistance and movement feels identical on all 6 exhaust valves on that side (I believe if the valve wasn't closing all the way, the spring/bucket would not return all the way). It will still run, just super rough. I believe it to be a burned valve. And I will almost certainly swap in a used engine before I bother pulling everything apart enough to replace a valve. I have a couple known good high mileage engines. Or maybe try to get a JDM, although those are a lot less common/cheap than they used to be.