1.8t diverter valve?

**stickybandits** · 10-04-2010 09:08 PM

i have a 1998.5 a4 1.8t and lately i have been hearing this noise when i let off the gas that sounds like a card stuck in a bicycle spoke but it can only be heard outside the car and when i have the windows down. most noticeable when driving next to barrier or something that sound can echo off of. again it is only when i let off the gas and put it in neutral, or down shift to slow down. my thoughts are that it could be the diverter valve but i'm not sure. don't think it is an exhaust leak because i have had recent work done on it and passed emissions test with no leaks. this issue has no effect on performance either and is throwing no CEL. any thoughts?

thanks guys

**tj4891** · 10-04-2010 09:36 PM

Sounds like your wastegate actuator. http://www.audizine.com/forum/showth...ight=wastegate

**voteforpedro** · 10-05-2010 11:43 AM

I get a flutter from the DV when I clutch down, most noticeable going 1st > 2nd. It's normal apparently...

**stickybandits** · 10-05-2010 06:20 PM

i'm not having any boost issues car pulls just fine, but it is very loud and it is a fluttering noise- with no boost issues i'm not quite sure, maybe shaft play in turbo?

**AudiNFS** · 10-05-2010 06:47 PM

Originally Posted by stickybandits

i'm not having any boost issues car pulls just fine, but it is very loud and it is a fluttering noise- with no boost issues i'm not quite sure, maybe shaft play in turbo?

cam chain tensioner? I have the same problem on my car. Actually got all wastegate components checked and they were fine and it still makes the noise. I hope it's a DV issue. That's way easier to fix

Does it happen at any time only when you let the gas down? Or is it only while the clutch is in. With mine, I can have it in gear and still let off of the gas and it does it down through the whole RPM range along with when I shift. or is your problem different?

**walky_talky20** · 10-05-2010 07:33 PM

If you are getting loud fluttering when you let off the gas abruptly while in boost, your DV is shot. Alternatively, the vacuum line to the DV may be damaged or fallen off, but odds are the DV has a torn diaphragm.

You should get this fixed soon. The fluttering sound is actually compressor surge, the spike in pressure is stalling the turbo. Too much of this is very bad for the turbocharger. It can actually snap the turbine shaft.

It is very easy to check the DV to make sure that is the issue. Just remove the end of the vacuum line that goes to the DV (remove it at the intake manifold). Then using a vacuum pump (or your mouth), apply vacuum to the line to see if it holds. You can also try to blow into the line. Air should not pass through. If you can easily blow through the line, it is junk. If it won't hold vacuum, it's junk.

On a stock car, the boost can be just fine, but have mad compressor surge. It doesn't always cause a low or no-boost situation. On a stock 1.8T, you can pretty much expect the DV to go bad by about 100k miles.

**stickybandits** · 10-07-2010 11:14 AM

Originally Posted by walky_talky20

If you are getting loud fluttering when you let off the gas abruptly while in boost, your DV is shot. Alternatively, the vacuum line to the DV may be damaged or fallen off, but odds are the DV has a torn diaphragm.

You should get this fixed soon. The fluttering sound is actually compressor surge, the spike in pressure is stalling the turbo. Too much of this is very bad for the turbocharger. It can actually snap the turbine shaft.

It is very easy to check the DV to make sure that is the issue. Just remove the end of the vacuum line that goes to the DV (remove it at the intake manifold). Then using a vacuum pump (or your mouth), apply vacuum to the line to see if it holds. You can also try to blow into the line. Air should not pass through. If you can easily blow through the line, it is junk. If it won't hold vacuum, it's junk.

On a stock car, the boost can be just fine, but have mad compressor surge. It doesn't always cause a low or no-boost situation. On a stock 1.8T, you can pretty much expect the DV to go bad by about 100k miles.

thanks for the input guys i am going to take a look at it this weekend, and yes it happens through the gears when i let of the gas and leave it in gear. hoping it turns out to be the DV

**AudiNFS** · 10-07-2010 06:00 PM

Originally Posted by stickybandits

thanks for the input guys i am going to take a look at it this weekend, and yes it happens through the gears when i let of the gas and leave it in gear. hoping it turns out to be the DV

I'd appreciate it if you would pm me with your results of this. I'm curious as well. Thank you