srirachaz

Ok so i decided to change my own oil this time and throw in an engine flush while i'm at it so i filled it with Liqui Moly Pro-line Engine Flush then 5-40 synthetic all done by the books then something weird happened:

Upon restarting the engine, i heard this loud, irregular knocking sound coming from the top of the engine so i shut it off after about 10 seconds thinking it might be due to the oil level. I then topped it off a bit and restarted the engine, this time the noise was gone and the oil level read fine so i drove off and went running some errands about 3 miles away and the engine remained noiseless along the way. I then came back to the parked car in about 30 minutes, started the car and everything sounded normal but, just when i was about to drive off the lot, the noise came back, so i pulled back in and shut off the engine again and restarted it, and strangely enough the noise went away, again, and this time stayed gone for a couple of days after some normal driving and some 50 some miles later with a seemingly smoother engine and no said noise. Then today the sucker decided to come back, in the same exact off-and-on pattern, and online search returned nothing so hear i am.

The car's a 2.0T Quattro with about 130K miles and has been running on name brand 5-40 synthetic at 5K intervals. Timing belt was replaced around 100K, and not long before that, PCV valve.

Prior to this, the engine does have a regular knocking noise likely due to the cam chain being loose, and my best guess is that the flush somehow further loosened the surrounding parts, but then that still doesn't explain the off-and-on characteristic..i'm super confused

srirachaz

video attached

John535is

The cam chain tensioner uses oil pressure. One idea, the oil flush has has flushed some gunk that's ended up in the chain tensioner that is stuffing up the pressure causing the chain tension to play up. The chain tensioner is not expensive, if you are going to pull it out to check it I would just replace it. The only real technicality is not letting the cams move while you remove the chain. You can buy cam locks pretty cheap as insurance if your concerned.

Dwes

Couldn't open the movie file, sometimes the vacuum line that is on the rear of the engine will knock on the pump until it warms up. Mine gets really bad the first start on a cold morning, but goes away after the temp is in the middle. It's pretty much the same spot where your cam chain and tensioner are located on the rear of the engine.

-Dave