Any Subaru gurus here? EJ25 DOHC vague knock

[Why_Anything]

I have this vague knock coming from the drivers side of the block. I used the stethoscope and the noise is only there from 1000RPM to 2000RPM then it either goes away or is drowned out by the sound of the motor. But it sounds like a knock. I know what piston slap is and i know what a lifter tap is but this seems strange. Its not very loud but its there. At this time im almost sure its not the TB tensioner.

I have some work i need to do my 98 forester but im hesitant because of this sound. I picked this thing up 3 weeks ago and you could not hear the sound till i got the exhaust leak fixed. It has 127K miles on it, TB/WP done at 106K, head gaskets not leaking.

My Fear is the start of a rod knock. I have driven it 500 miles with this sound it has not gotten worse.

this video is from behind the drivers side axle, you can hear the sound in 1000 rpm range then it goes away as i up the RPMS and if you notice its not there at low RMPS

https://www.youtube.com/watch?v=7uxLleIVMqQ you can really hear it after the 20 second mark

 

[Bottom_Feeder]

Rod knock, probably a spun bearing, sorry to say. It's what killed my 2001 RS after 114k miles and it's pretty common. Mine was louder but the tone and frequency was the same. The local highly-regarded Subaru shop diagnosed it (by ear) and the guy I sold it to confirmed it (by disassembly).

I figured after a lifetime of 3.3k oil changes with name-brand synthetics and no abuse would have avoided the issue, but no. It was a sad day...

 

[Why_Anything]

ugH!

 

[Why_Anything]

I just looked i actually have put over 700 miles on it with this sound. I thought a ej25 spun bearing sound would get much more intense with high rpms not go away.

 

[Bottom_Feeder]

That's a good point, of course. I had my doubts initially also since it sometimes did not sound that bad. But it was broken all the same.

 

[Padawan]

Just to be sure, check if your fuel line has a damper on it. You should see the lines running past the driver's side strut tower and washer tank. If one of them has a black device placed in-line that's the size of a golf ball and shaped like an upside down mushroom, that's the damper (it appears some '98s were equipped with them while others weren't). If it's there, put your stethoscope on it and see whether the noise is coming from it.

One of the dampers on my wife's car went bad, and it made a metallic tapping noise that certainly sounded like an internal bottom-end engine issue. It was difficult to track down until I read about others with the same issue who traced the problem to a faulty damper.

 

[Why_Anything]

ill see.. this has me so stressed out.

 

[caprice_2nv]

I don't know. It seems like every older Subaru I hear running has a knock like that, including the 98 outback my ex girlfriend had. I assumed it was piston slap or it would have gotten worse fast. We sold the car because it was way to expensive for us to keep up, and she shared my 83 caprice with me.

 

[JTK]

We've had many EJ25s in the family. Some approaching 300K miles. They typically don't sound pretty on a cold start, my new FB25 included. I've never seen one have a connecting rod bearing failure or any bottom end issue for that matter. If you've got good oil pressure, this could be a lot of things.

 

[Trav]

I have one making noises for over 6 years, kill the spark to each cyl one at a time and see if it goes quieter.
If it almost goes away with one that's probably a rod bearing on that cyl if not its something else, possibly a dropped valve guide on that engine.

 

[Why_Anything]

This is a great idea! Ill try this later on tonight.

 

[gathermewool]

My '97 Legacy GT sounded similar, but it's hard to tell. Mine exhibited classic piston slap that went away almost entirely when the engine was warm and was non-existent after a long drive. On really cold mornings, it was scary loud.

 

[Why_Anything]

Originally Posted By: Trav
I have one making noises for over 6 years, kill the spark to each cyl one at a time and see if it goes quieter.
If it almost goes away with one that's probably a rod bearing on that cyl if not its something else, possibly a dropped valve guide on that engine.


Did this tonight, the sound did not change at all.

 

[Trav]

Good, so its probably not a bottom end bearing. It could just be from piston slap Rotella T5w40 may help it seem quieter or the noise is coming from something else.
A badly adjusted (very loose) valve, seized rocker roller can make noise like this as can exhaust valve guide(s) that have slipped which is common.
Other possibilities would be a cracked flex plate or dented oil pan.

 

[sxg6]

Not terribly familiar with the older subarus, but on some subarus the timing belt tensioner can cause a knocking sound if it has gone bad. I'd see if you can figure out where the tensioner is on that engine, and see if the knocking sound is louder there.

 

[Why_Anything]

Originally Posted By: sxg6
Not terribly familiar with the older subarus, but on some subarus the timing belt tensioner can cause a knocking sound if it has gone bad. I'd see if you can figure out where the tensioner is on that engine, and see if the knocking sound is louder there.


i checked that, it was fine

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Originally Posted By: Trav
Good, so its probably not a bottom end bearing. It could just be from piston slap Rotella T5w40 may help it seem quieter or the noise is coming from something else.
A badly adjusted (very loose) valve, seized rocker roller can make noise like this as can exhaust valve guide(s) that have slipped which is common.
Other possibilities would be a cracked flex plate or dented oil pan.


I think the noise is from the top end. Ill try rotella and see if it masks the sound at least so i dont hear it.. lol

 

[caprice_2nv]

That's good. When I priced out the timing belt and water pump kit for that engine is when we decided to get rid of it ASAP.