Buzzing on decel?

Post by **priapism** » 13 Apr 2011, 08:07

There's a buzzing behind the drivers' side dash when you lift throttle at highway speeds. It only happens when the car is moving so it's hard to diagnose. My guess was the relays but I pushed them in good and it still made the noise.

Post by **priapism** » 15 Apr 2011, 01:04

Still doing it after a 700 mile trip. Every time you back off at speed there's this weird buzz. I don't have a clue.

FCPEURO · Post by **FCPEURO** » 18 Apr 2011, 17:03

That is an odd thing. Can you by any chance post a video or sound clip of the noise. I know this will help a lot.

Post by **kcodyjr** » 18 Apr 2011, 18:37

+1 recording.

What model and year of vehicle?

Can you put a name to what kind of materials might be banging together rapidly? Plastic on plastic, plastic on metal, metal on metal, any kind of descriptiveness you can come up with actually.

Does the sound seem to move around if the windows are open? Does it seem like it could be on the engine side of the firewall, or are you fairly certain it's originating within the dashboard?

Post by **priapism** » 18 Apr 2011, 18:46

I am not sure where it's originating. It sounds like it's in front of the driver. It sounds electric. Its an 01 S60 2.4t. I'll try to get a recording. It only happens at speed which makes diagnosing difficult.

Post by **kcodyjr** » 18 Apr 2011, 19:45

Sounds like the circumstances when the blow-off valve would actuate.

My guess is, if it's really inside the car, it's whichever relay controls the turbo control valve. If it's really under the hood, I'd look at the TCV and the linkage to the wastegate. Check for obvious mechanical issues (rust, sticking, loose, broken) and also look for leaks in those vacuum lines.

Post by **priapism** » 18 Apr 2011, 19:50

I sprayed carb cleaner around looking for a vacuum leak and didn't find one. I pushed on the relays in the fusebox under the hood and it didn't help anything. I'm not sure where the wastegate is but that's a great idea.

Post by **kcodyjr** » 18 Apr 2011, 19:54

The waste gate (with linkage and solenoid) is on top of the turbocharger, just in front of the firewall. It has some heat shields you'll need to remove to see what's going on.

The turbo control valve should be bolted to your airbox. Check electrical connections there, too.

Does anyone know offhand which relay this would be?

JetMechGAC · Post by **JetMechGAC** » 19 Apr 2011, 21:38

It could also be a simple as a loose gauge cluster bezel. Try pressig on the trim bezel or instrument cluster or any part of the dash in front of the driver to see if it goes away. If that doesn't work, is it a buzz that you can only hear or can you feel it too?