gavs wrote:It's still under warranty yeah? If so, don't worry about it. If you think of how many of those turbos are pumped down a production line, you are always going to get production faults, it's a fact of life. Good thing it went into limp mode so it protected the engine, so now, you just get teh replacement fitted and off you go again:)
Words of wisdom there.
And exactly what the service advisor (or whatever they're called) behind the desk told me.
So. The turbo was changed today under warranty. First thing I noticed after firing her up on the dealership courtyard, was that the engine sounded like a cement mixer full of small rocks! Or a very old and loud diesel engine with a sharp rattle!
Immediately went back inside to talk to the service advisor, and he came out to listen to the engine. The longer it idled the quieter the noise became, but it was still there when I gently pumped the throttle, keeping the revs very low. The service advisor pinpointed the noise to the wastegate actuator rod. When he slightly pressed it the noise went away.
Back inside he showed me a service note from VW concerning the noise. Evidently it's the electric pressure regulator causing the actuator rod to vibrate at idle or low revs (under 1300 rpm). Although the turbo is new, manufacturing tolerances mean that some units may suffer from this noise while others are perfectly (relatively) silent. My new one just happened to have bigger tolerances....
There's an engine ECU update that should solve this, my car was booked in for the update next Thursday. He couldn't say for sure what the update does, but he thought it probably switches off the electrical pressure regulator at idle and very low revs, so the actuator rod won't vibrate. After all, the pressure doesn't need to be regulated at idle since the turbo isn't spinning up yet. Kinda makes sense I suppose.
Funny though that the mechanic who changed the turbo hadn't noticed the noise when he started the car for the first time? Bit of a bummer having to take the car to the dealer again separately for the update. But I must still hand it to my dealership and the service advisors, they really seem to be genuinely interested in their products and know a lot about them. So all in all I'm very happy with how the VW service works in my hometown at least. The servce advisor told me that if the update won't help to solve the noise problem, then they'll change the turbo again!