Broken Camshaft?!? Help me figure this one out.

[newsance]

This will be long, but hopefully interesting. I need some engine sleuths to help me explain this one.

 

I'll start with what happened-

 

1990 Subaru Legacy Wagon AWD Auto with 138k on the clock.

 

I was driving home from a 200 mile round trip. About 50 miles away from home, in an area absolutely deserted, the car suddenly lost power and started sputtering, missing, and smoking, with a lot of lost power.

 

I decided to keep driving it to see if I could make it home, for one, I had bought the car for $750 and a 50 mile tow would cost about half that, so I decided to risk it.

 

I made it about 25 more miles before the car then lost even more power, to the point where it would not stay running in gear. At this point I took my losses, and had it towed home.

 

At first, I was sure that the timing belt had skipped. So, it was to my complete amazement to find that it had not- all the pulley marks lined up perfectly.

 

At a loss for how it was running, I tried a compression check. Surprise! Zero compression on the 2 driver's side cylinders.

 

At that point I was stumped. The only thing I could come up with was a massive head gasket blowout between the cylinders, but if that was the case, I would have had milkshake oil or oil in the coolant, which I had neither.

 

I bought another Subaru and let this one sit for most of a year. Finally, I decided I needed it out of my garage and tore into it to see what was wrong, with the thought of fixing it and selling it.

 

Things I found:

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1. The camshaft was snapped in two pieces just behind the oil seal housing.

 

2. All bearing surfaces on the camshaft look fine. It did not seize in a journal, and both pieces freely spun.

 

3. The camshaft keyway for the cam pulley looked perfectly fine (not chewed up) but there was no key to be found.

 

4. Rocker arms look fine, and I don't see broken valve springs. Aside from the broken cam, things look normal under the valve cover.

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I've NEVER heard of a Subaru breaking a camshaft. As far as I can figure, the only 2 ways enough force could be generated to do this would be if a journal seized, or if a valve got jammed against the piston.

 

As I can't see that a journal seized, it must be valve interference. Right?

 

My temporary hypothesis is that the cam gear could have shifted position on the cam as there was not a key to hold it in place for some reason. This, the car starts to miss and lose power. Eventually it shifts so far that a valve contacts the head, and the camshaft snaps.

 

 

Problem with this hypothesis-

 

1. Why did the cam snap instead of the timing belt shredding or skipping? The belt did not jump- it kept the exact same relationship with the cam gears.

 

2. If the cam gear shifted position on the cam, sending that bank out of time, wouldn't it continue to spin? If it had already started to spin, I don't see how it wouldn't give before there was enough force to snap the camshaft.

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The main point of this exercise is to see whether there is a point to continue working on this engine or to just junk the car. I'm not willing to replace the head, and I can't imagine the valves would still be working if they smacked the piston hard enough to break a camshaft.

 

What do you think?

 

:popcorn:

[Hondasucks]

It could have been a faulty casting or something, I think I have some EJ cams lying around if you need one.

 

Keep in mind that even though the car was only $750, it's probably cheaper and more worth it in the long run to fix it, rather than find another $750 car with new problems.

[newsance]

It could have been a faulty casting or something, I think I have some EJ cams lying around if you need one.

 

Keep in mind that even though the car was only $750, it's probably cheaper and more worth it in the long run to fix it, rather than find another $750 car with new problems.

Actually, I bought another Subaru shortly after this happened as I needed to drive cross country. The only reason I was looking at fixing this was to sell it (and get it off my property).

 

And I am not putting the money and effort into replacing the head, and possibly the whole motor if the pistons are badly scarred. Unless somebody can come up with an explanation that doesn't involve the valve smacking the head hard enough to break a cam, I'm not tearing this motor down any more.

[lostinthe202]

Isn't this a non-interference engine?

[hankosolder2]

As lost in the 202 said, it's a non interference engine, so slipped valve timing shouldn't cause internal damage.

 

Assuming the '90 EJ 22 is similar to the later EJ22 engines, there's a spot on the camshaft and cam sprocket which looks like there should be a woodruff key in it, but there actually isn't supposed to be one in there. There's a shallow pin which comes out of the cam sprocket to locate it to the flange on the front of the camshaft.

 

Perhaps it dropped a valve, a valve guide or something got into the combustion chamber and was interfering with the valve opening. It sounds like one cylinder failed (say a dropped valve) then as you continued to drive, the broken part jammed one of the other valves in that cylinder and caused the cam to snap, disabling the other cylinder on that bank.

 

Nathan

[subaru360]

These engines are dirt cheap and plentiful in pick a part yards. They are also easy to swap. You could probably have it up and runnning with a used one for a $100 and a few hours work. That's what I would do.