Help identifying engine knocking sound

Hello, I am going to look at an 09 Legacy 2.5 that the owner says has an engine knocking sound. Is there a way to distinguish the bad timing tension sound from rod knock? Ex. Noise present at idle, cold temp only, above 3k rpm only etc.

With a stethoscope, or a long screw driver which you put ear on the end of the handle, you may be able to tell if one of the idler pulleys for the timing belt is the issue.

 

You can remove the drive belts and start the engine to verify its not one of those idlers.

I'd walk away from any subaru with a "knock" regardless of source.

If you think it might be a idler it might be worth it, but I would price it assuming it is internal engine knock.

 

Is it a GT or 2.5i? If a GT has the turbo been recently replaced? Was the timing belt done and if what brand of components were used?

From what I can remember, I think the driver side timing belt cover is easy to remove, just 4 bolts or so holding it on. Once off, I'm almost positive I was able to just barely see my timing belt tensioner from the side, looking towards the passenger side. Just enough to see if it was bouncing up and down.

Why not have them pull timing covers and look? If the tensioner is borked enough to make a knock then you should have some noticeable slop in the belt

Appreciate the responses. It's a 2.5 non turbo, 65k miles. If I'm listening, the timing tensioner is towards the driver's side right? I'll try to get a video if I go look at it.

That tension knock is sometimes almost indistinguishable from rod knock. Only way to be sure is pull drivers timing cover and start it. Easy and takes minutes

I put a yellow box around the tensioner, it's between the alternator and ac compressor is, and where the pin makes contact to make the noise. The red and blue lines were already there, borrowed the image from the link below.

https://www.ultimatesubaru.org/forum/topic/171377-ej253-timing-issue/

Edited October 6, 2020 by apexi

worth a quick look for metal shavings in the oil. if there is metal it would be confirmation of rod knock vs tensioner knock.

Thanks again for the responses. I'll have a look at the oil as well as listen near the driver's side timing cover. I'll take tools to remove the timing cover just in case. The price is a bit high at the moment, but I figure if I can get it under 2k, it would make for a great winter car. I don't mind doing work to it, but would be more hesitant to buy if I know will need an engine rebuild.

Ok a little more information, I'll be looking at it tomorrow. The owner said the car has been sitting for almost a year. Also mentioned that when he started it today, the noise wasn't as audible. Would that seem to indicate anything since it isn't heard all of the time?

When you test drive it, I would think you'd want a 10 mile drive at least...you want to get it good and warmed up.

Check the oil level first.

So I went to look at it. It definitely rattles and clanks but it doesn't sound like it's all in the engine. Almost like a heat shield underneath, or something is loose. Here's the odd part. The timing cover, fans , and accessory belt were all off the car. Owner said some work has been done on the coil pack. The grenade pin was still in the tensioner. The owner wasn't sure if any timing work had been done....which with the grenade pin still in the tensioner, I'm pretty sure that has been replaced. I think I will pass, but part of me thinks it could be put back together and revived with some work.

The pin should be out which could cause some issues, it could have skipped timing. (or it has a recently tensioner trying to fix the issue) The timing covers haven't been on in a while. The water pump and the cogged idler shouldn't be rusty. I think its a good idea to skip this one.

Wait.... it was started with that pin still in??? I’d walk unless the cars in good shape and you are getting it for a song. Sounds like you’re getting into someone’s back yard project.

 

But! If you are interested in it, with the pin still in it will knock like hell since the belt won’t be tight and the cams are literally spring loaded so they will advance and retard between strokes. Motor might be in ok shape, but I’d put tension on the t-belt and do a compression and leak down test before you go any further. Then if those are well, replace all the timing stuff and drive it.

Wait.... it was started with that pin still in??? I’d walk unless the cars in good shape and you are getting it for a song. Sounds like you’re getting into someone’s back yard project.

 

But! If you are interested in it, with the pin still in it will knock like hell since the belt won’t be tight and the cams are literally spring loaded so they will advance and retard between strokes. Motor might be in ok shape, but I’d put tension on the t-belt and do a compression and leak down test before you go any further. Then if those are well, replace all the timing stuff and drive it.

 

Yep, I was surprised after I looked closer at the pic. It might be worth taking a chance for 1500 or so, but not at 2k.

It might be worth a shot at $500-750, definitely not $2k.