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Brucey
'17 3.6
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Discussion Starter #1
Title.

I was told the vehicle had 'snapped a timing belt' but when I got into it the belt was intact but had walked off of the upper left idler and burst through the cover.

Tensioner was also not correctly functioning. After retiming it and installing a new tensioner I did a compression check.

I figured when I bought it I needed new valves or just a redone head and call it a day.

But I showed 0 psi on all 4 cylinders.

Thinking my old compression gauge had broke (o ring crumbled) I bought a new one.

Same thing.

I was told that this isn't likely but I don't see how it isn't knowing the circumstances.

So I guess I'm just looking for a second opinion other than my own here?
 

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Have you redone the heads? The way I read you post you have NOT redone the heads. If the valves are bent they are not sealing and you will get 0psi.

Need more info. Have you done any work to the car? What all have you rebuilt, check, worked on

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Brucey
'17 3.6
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11,904 Posts
Discussion Starter #3
Have you redone the heads? The way I read you post you have NOT redone the heads. If the valves are bent they are not sealing and you will get 0psi.

Need more info. Have you done any work to the car? What all have you rebuilt, check, worked on

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I have done no work to the car. I have only retimed it and installed a new Aisin timing belt, tensioner, and idler to check compression.

The idler that was ripped off I needed to helicoil the threads since it would not tighten.

I have not redone the heads. They're as I got it.

That was what my plan was but I figured slapping a belt on to check compression was worth a gamble. But after getting 0 psi in all of them I was told I'm doing something wrong.

I've done timing belt and head gaskets on these before. I've run compression checks before.

I disconnected the crank sensor to cut fuel and spark to test compression.

Thank you.
 

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If the valves are bent the engine cant hold compression. If the belt came off the Subarus are interference engines then the valves are most likely bent. They will not seal and you will get 0 psi compression.

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Brucey
'17 3.6
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Discussion Starter #5
If the valves are bent the engine cant hold compression. If the belt came off the Subarus are interference engines then the valves are most likely bent. They will not seal and you will get 0 psi compression.

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What are the chances all 4 cylinders wrecked?
 

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Outback 2011 3.6R Premium
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Brucey, typically only the valves in one head are bent but it appears this engine ran long enough to bend the valves in both heads (and therefore there may also be some damage to some of the pistons)..

You will need to disassemble to confirm this and if it is only valve damage new valves or new heads will be needed.

Seagrass
 
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Brucey
'17 3.6
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11,904 Posts
Discussion Starter #7
Brucey, typically only the valves in one head are bent but it appears this engine ran long enough to bend the valves in both heads (and therefore there may also be some damage to some of the pistons)..

You will need to disassemble to confirm this and if it is only valve damage new valves or new heads will be needed.

Seagrass
Awesome. What I figured but a friend told me all 4 isn't possible. Gonna take the heads off and go from there.
 

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The valve train is wrecked for sure.
If the person was accelerating heavily when the belt came off and then rpms were high the more damage done.

The valves wi need replaced and heads will "likely" need tongo.to a machine shop.

Probably cheaper to buy used heads.

You will not known the condition of the cylinders until you open the engine up. If the damage occured at low RPM and none of the valves broke and fell inside then the cylinders are likely fine. If a valve fell inside and was smashed against the head then you should rebuild the bottom end as well.

Was there alot of noise when you cranked the engine for the compression test?

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@Brucey that's a good sign. If a valve was broken off inside it would have made a racket.

Next thing is to pull the heads and check the cylinders. Then look for heads and a gasket set. I would do the head gasket while you are in there.

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2006 Outback 2.5i manual
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159 Posts
Curious to see how it looks when you're able to tear into it!

Not that it really matters now, but, does the engine run after you put in the new timing belt? Would be amazing if it does (though I'm sure the answer is no).
 

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2020 Outback Premier 2.5i
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If you did a leak down test it should confirm bent valves?
 

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If you did a leak down test it should confirm bent valves?
No, a LDT just tells where the leak is. Pinpoints intake, exhaust or rings.
 

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So? Air leaking from throttle body, bent intake. Air leaking from exhaust, bent exhaust valves. Your comment makes no sense to me.
 

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Don't have to be "bent" to leak air. Just a bad valve seat.
 
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2020 Outback Premier 2.5i
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Bad seats = maybe 10 / 15 psi leakdown from 100 psi
Bent valves, maybe 80 psi leakdown. Maybe more. That's the point of doing the test.
I would have suggested scoping, but I imagine OP neither has one or could get one; at least one that will bend back to look at the valves.
 

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2014 3.6R Limited
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1,080 Posts
Do you R+R heads without replacing the head gaskets? :devilish:

@Brucey that's a good sign. If a valve was broken off inside it would have made a racket.

Next thing is to pull the heads and check the cylinders. Then look for heads and a gasket set. I would do the head gasket while you are in there.

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2010 Outback 3.6R 2014 Legacy 2.5i 2003 Legacy L special edition (retired to backup)
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that thing spun way too fast so yup no compression...

first thing I would do is verify timing
second thing I would do is remove heads and make sure no valves are bent

EJ253 is interference engine so it is more than likely valves kissed the pistons
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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The only way there is 0 compression on all 4 cylinders is if the crankshaft gear is about 20-45° or so off from the cams or by some freak accident valves on every cylinder got hit. The latter would mean that intake and exhaust valves would be damaged. Doing a leak down is moot when no matter what the problem is being caused by, the engine would have to be removed and disassembled to correct it. As long as the timing is correct now.

There is another way, but since the engine was running prior to the belt popping off it's unlikely. The other way is valves are out of adjustment on the 4 cylinders and can't close or a good number of stem seals or seats is lodging them open. A leak down would tell you which is open on each cylinder, but that still leads to a tear down.

Are you sure the timing mark on the crank is correct?
 
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