"Tapping" sound 3000 rpm, slight load.

Hello all. I'm New to this forum (as a member anyway) and new to turbo Subarus although my recent purchase has already gotten me pretty well acquainted with many of the basics. While I am new to the turbo powertrain I'm pretty familiar with wrenching on Subarus as my last two DDs were an '02 Legacy GT wagon and a 94 Legacy GT wagon, and I've also owned several Outbacks and a Forester that were project cars (headgaskets, bad transmissions, etc).

Anyway, on to my question. I have a 2005 GT wagon with 123,xxx on it and no modifications that I bought several months ago. I'm experiencing a strange tapping or maybe you could even call it a knock. It's most noticeable around 3k rpm, never present below about 2700, and only occurs under slight load such as when I'm cruising at 75 mph. Let off the pedal, no tapping, get on the pedal a little more (or a lot) and the sound goes away as well. Another observation is that it doesn't really happen until the engine warms up. I've checked exhaust heat shields and can't seem to get any of those to make noise when I pound on them. My next thought is to replace the turbo inlet pipe because the rubber where it clamps to the turbo looks pretty shot and my thought was that perhaps a leak after the MAF was giving me a lean condition under just the right circumstances. Any of your thoughts or experiences on this matter would be welcome.

Thank You.

I should also add that I've recently done a timing belt service on the car and changed the tensioner. I've heard that the tensioners can rattle when they start to get weak but that's been ruled out. Also just holding the engine at 3000 rpm in neutral or with the clutch in doesn't cause the noise to happen unless you blip the throttle some.

Got a log? Otherwise it could be a million things. The fact that you recently serviced the timing belt just gives you a place to start looking. Yes the tensioners get weak. I have even seen brand new ones not up to snuff and we dont install them.

Data logging is not something I'm familiar with other than hearing it mentioned on this forum a few times. I've got the app "Torque pro" for my Android phone which I think might be able to log data but I'm not sure. Anyone familiar with it or have a recommendation for the best way for a beginner to be able to get a log?

This noise was present before I did the timing belt service and there was no change after. Other relevant info would be that I bought it with a brand new turbo that the PO had installed shortly before I bought it. Also a few months ago I got a CEL for PO021. Replaced the OCV and still had the light come back. Changed the oil and been good ever since.

Getting a P0021 after the turbo install is not a good sign.

Get a stethoscope.

Subscribing. I'm having a very similar experience. No major maintenance or mods recently, but am pushing 100k, so almost timing belt time.

M Sprank, can you explain what you mean about getting po021 after new turbo? My understanding is the turbo failed because of a clogged banjo bolt screen on the right side of the motor and my po021 code was likely from a similar blockage on the left side of the engine but with less consequences because only the OCV is affected. Am I wrong about that?

It looks like I can data log with my phone app so I'll fumble with that tomorrow and see what I can get. Anyone have any thoughts on what data from what sensors might be important?

You want to log using Romraider. Go to the tuning forum and click on the sticky.

The CEL means there is still debris in the oil system. That another oil system component is failing. It basically proves that the motor was not properly flushed with the turbo swap. You sir have what I call a ticking bomb. I am OCD (admittedly) but I would be pulling the banjo bolts to check both screens, pulling the pan to clean it, pulling the oil cooler to flush it (or replace it) and replaceing that oil control valve at a minimum.

Y u no just clear code?

Good luck, OP!

I hear you on your concerns about debris from the turbo in the oil and that has been a big concern of mine too. I've tried to take a more optimistic approach and assume that same gunk that blocked the turbo banjo screen was also restricting the OCV banjo screen. The screen on the turbo side was removed when the turbo was replaced. When I got the CEL for the bank 2 OCV I first replaced that OCV and then cleared the code. When it came back on again I changed the oil and the light had stayed off for 4000 or so miles now. When I did that oil change I actually cut the old oil filter open to see what was inside and didn't see anything at all that looked remotely metallic, for what that's worth.

If it hasn't grenaded in 4000 miles, you might be ok. Or throw a bearing tomorrow.

Only time will tell.

^ this.

Also, I have seen some odd cv joint issue with Subies. Sometimes a clicking CV sounds like motor noise from the cabin. But when a bystander is involved, what seem rpm related can be heard from outside at all rpms. Maybe wishful thinking, but is far cheaper than a motor/turbo.

My noise has recently worsened to where it's now obviously a rod knock. Goodbye money I haven't earned yet.

Motor not cleaned up after a blown turbo. Rod bearing failure to follow. Unfortunately, this is a normal occurrence if the motor is not clean.

I have one at my shop now that was catastrophic. Nothing usable in the block or heads. Complete trash.