2006 Forester engine noise- rod knock, valvetrain, injector?

[Stevo F]

Bought this 2006 Forester earlier this year, partly based on receipts for headgasket replacement. It started overheating within 100 miles after buying it, so I got over to my mechanic who confirmed it was an internal headgasket leak (likely cheap headgaskets were installed 45K milers ago by a previous owner).

I had my mechanic install OEM EJ255 turbo MLS headgaskets, and an Aisin timing kit. It ran well except for an oil leak from the driver's side front cam seal that we couldn't diagnose Several cam seals later, we decided to go ahead and install a used head. The head was not warped but the valves were in poor shape, so had them replaced as it was failing a leakdown test (leaking into the exhaust). Anyway, it was all put together runs smooth, no oil leak or headgasket leak but I noticed more engine noise from before when pulling it into the garage.

I've uploaded a video of the noise at the link below. I'm fearing it's a road knock (my mechanic noted he may be hearing a little low end noise) and the previous owner could have overheated it badly. Perhaps my mechanic left a little too much valve clearance? He did remove and reinstall an injector so could it be injector noise? Also, it is a 205K engine so just normal high mileage noise? One thing I noticed is that the noise gets louder as the engine warms up (which is opposite of what something like excessive clearance or piston slap does)

 

Edited December 24, 2022 by Stevo F

[forester2002s]

Could it be a belt-tensioner flopping around?

[Stevo F]

47 minutes ago, forester2002s said:

Could it be a belt-tensioner flopping around?

Timing belt tensioner is new and actually the noise is a bit loader towards the center or rear of the engine, and on the driver's side.

[nvu]

slow knocking like that is valve train related; slow pace like sewing machine. 

piston/rods related knocking is faster like machine gun speed.  it doesn't sound like rod knock here.

[Stevo F]

On 12/24/2022 at 12:13 PM, nvu said:

slow knocking like that is valve train related; slow pace like sewing machine. 

piston/rods related knocking is faster like machine gun speed.  it doesn't sound like rod knock here.

That makes sense since a rod knock with theoretically occur with each crankshaft revolution, but a valve with too much clearance will only open every other crankshaft revolution, so only half as frequent. My mechanic weighed in that is sounds like valvetrain to him as well.

[nvu]

Was it making this noise with the leaky cam seal head before? The new tensioner could blow a seal if it was retensioned too quickly.

Either way, have your mechanic look at some of these videos, https://www.youtube.com/results?search_query=subaru+timing+tensioner+check

 

[Steptoe's photos]

one month on ....having had "rod knock" in an EJ due to oil supply run too low, this does not sound like my rod knock

[idosubaru]

3 hours ago, Steptoe's photos said:

one month on ....having had "rod knock" in an EJ due to oil supply run too low, this does not sound like my rod knock

I’m unsure but it doesn’t seem like rod knock.

Since it didn’t do it with the previous head then Occam’s razor suggests it’s probably something with the:

1. Used head

2. Timing belt components (since those were removed for the head swap)

3. Very unlikely it’s something that just happened to start making noise exactly when the new head was installed. 

[forester2002s]

Sure sounds to me that this is valve-train related (in olden-days, this would have been called 'noisy tappets'):

- either incorrect clearances around the cams;

- or in need of an oil-change.