Mysterious Subaru Engine knock.

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Originally Posted By: KrisZ
Does it have some sort of internal shaft balancer thingamajig?

No it doesnt.

I took this thing apart twice and it wasn't until i cleaned parts in the ultrassonic cleaner that it showed up.
The bad part felt okay, looked ok and seemed to operate fine even after being cleaned with brake cleaner.

I only threw them in the ultrasonic tank to make darn sure i could get them as free of oil as possible. I was ready to pop the head.
Thats a pretty good hint and its not the lifters or a cam.
 
Originally Posted By: Rolla07
Timing belt tensioner or cam belt tensioner?


I think that could be it! They can make a knocking noise when they are about to give out.
 
Sheesh, I even work in the parts department of a Subaru dealer and this is stumping me. Only other thoughts:

1. Idle air control valve
2. Backpressure transducer for the EGR
3. EGR valve
 
Originally Posted By: ethangsmith
Sheesh, I even work in the parts department of a Subaru dealer and this is stumping me. Only other thoughts:

1. Idle air control valve
2. Backpressure transducer for the EGR
3. EGR valve


PM sent.
 
can't recall if this thing has an EGR valve...?

clutch assy--- big metal lever that poke out from the bell housing near drivers firewall?

PS pump is driver's side and spins at near engine RPM speed?

but it can be dipped in a solvent can--- so I'm going with some sort of valve that thinks very highly of itself.??
 
I was going to mention timing belt tensioner, as I had that issue in my 2000 subaru. But, Rolla07 mentioned that already.

Whats left? Carbon knock? Misfire?
 
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This is the problem.The mirror finish is on the roller is not there because the chemicals i use in the tank puts a protective coating on parts until wiped off or washed off with oil or fuel.
It was mirror when i put it into the tank, the chemicals are harmless to metal its just optical.

When i first checked this it rolled smooth with normal resistance from oil in the bearing, the second time also.
It really looked and felt like all the others, i didn't look at an closer as it had a bad lifter (not on that cyl though).
Even after i got them clean and oil free it still felt okay until i put pressure on it and rolled it on a paper towel. That's when i felt something move.

Then i realized one or more of the needles has a flat spot!
When it moved it was quiet but if it stopped on these needles against the flat spot it would resist moving and knock. The heavier oil also created additional resistance.

The rest are all fine i checked them the same way, the cam thankfully didn't get damaged, the lobe height is within spec.
This one almost beat me.
 
Originally Posted By: Trav
Even after i got them clean and oil free it still felt okay until i put pressure on it and rolled it on a paper towel. That's when i felt something move.


Is the "put pressure on it" part of a standard diagnostic procedure that you forgot to do, or did you have one of those "divine intervention" moments that made you try this technique that caught the problem (a bit of good luck, when near the end of your rope)?

Either way, congratulations on a great diagnosis. That feeling when you do something like this is priceless.
 
Normal procedure is visually check for scores and damage and make sure they rotate smoothly with no radial play.
It passed all this criteria. Cleaning them in an ultrasonic cleaner then checking them dry under pressure was sort of a hail Mary pass but i knew there was a noise somewhere with this cyl and strongly suspected it in the top end.

Never so happy to find a bum part. LOL
 
I don't know what to think. The cam is lubed by the squirter above the roller and its fine and was wet with oil.
Maybe just an old part that gave up, i cant find any reason for root cause.

Its all together and runs quiet as a church mouse. No noise at all.
 
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