Whoosh sound during accelleration

'99 NB TDI, 110K miles. I have a whoosh sound coming from the engine compartment during accelleration when the turbo spools to around 10 psi.

I have disconnected the boost gauge, no difference.
I have check the hoses from the intercooler to the turbo and the hose from the intercooler to the EGR. Nothing has popped off or has a hole in it.

The snorkel has been gone for years, so it's not the snowscreen.

Suggestions?

It sure sounds like something in the intake after the turbo. I had a similar problem a while back. I moved the hose clamps that connect the lower intake line from the turbo to the intercooler, right where the hose connects to the intercooler. I didn't put the clamps back exactly the way they were. They looked like they would seal just fine, but they were slightly out of position. I heard that sound during acceleration above 3K rpm. I moved the clamps back to the original position and it stopped.

Perhaps it's a vacuum hose? Are you absolutely positive that it's not BEFORE the T-bo? Aircleaner box seal?

This happens when the snowscreen is clogged enough for the bypass to open. If this is the case, clean your snowscreen and the problem will go away.

EDIT: Me = moron. I didn't read the end of your post. My bad.

Along with the previous suggestions, a split in one of the rubber hoses may not be obvious to see, but will open under boost. Since you have a boost gauge already, try backfeeding compressed air into the IC pipes from that hole. You can then presurize the system and listen for the leak. Thats how I found my leak. It was a hole in the upper intercooler pipe where the power steering pulley rubbed through. Once I applied the air pressure, I could hear where the sound was coming from and easily found the location.

My thoughts exactly. Unfortunately, I don't have the expertise or equipment (or time) to pressurize the intake system, so off to the mechanic it goes on Tuesday. I'll report back what they find. It's got to be a split somewhere in a hose that opens under pressure. I've even looked at the vacuum hoses, and nothing seems out of sorts. I guess the best way to find the problem is with pressure.

It doesn't take any expertise or special equipment to pressurize the system. I just used a 12v compressor that plugs into my ciggarette lighter and attached it to the boost line. If you don't have one of those compressors, they are quite cheap at Autozone. I bought mine for $10 on sale. Or, go to a gas station and use their air compressor. The only thing you may have to do is to make some kind of adapter to connect the hose to the boost fitting. Les than $1 worth of parts can be used. I wish had taken pictures when I did mine. It really was quite easy. For reference, I have these old pictures of when I did it the first time, but I had a small tank that I was able to use for the test:



As you can see, the fitting from the back of the boost gauge fit right onto the little tank I had. I pressurized the tank with the 12 air compressor. It wasn't a lot of pressure, but I could hear where the leak was coming from:



I fixed it by plastic welding the hole. I used some black plastic from an old oil bottle cap as a filler:


It's not pretty, but sure is strong. I also put a piece of steel bug screen over the hole to add strength. Epoxy or JB Weld were also possible alternatives.

Wingnut, great pics on the how-to.

A place I saw recently was on the hose coming out of the turbo to the "pancake pipe" in the fender well. No way you could have seen the split unless the hose was removed. Then it was obvious.

Yeah, I had one there too. The joint where the rubber hose from the turbo connected to the plastic 'pancake' tube was not secure. The connection was deformed and I had a boost leak there. I just never noticed it until I fixed the bigger hole and still heard the whooshing noise. It wasn't as loud, so maybe thats why I never noticed it before. But since I was specifically listening for a leak to see if my repair held, I noticed it. The fitting was all deformed from a previous accident, so instead of buying another tube, I just made a new one out of exhayst pipe. Here were the pics of that one:


You can see how the hole was not quite round . So the fit between the aluminum fitting and the plastic pipe was not air tight. I just cut off the alluminum coupler and clamped the rubber hose right onto the pipe I had bent up at a local muffler shop for $10:


Here it is installed:

Cool! I think I can do that. Thanks much.

In the meantime, I am being very careful about accellerating too hard and having the turbo work overtime to sustain the required boost. Is it possible to overspin the turbo this way?

Result: there was a 3/4 inch split on the inside elbow of the top intake hose that connects to the EGR valve. The only way to find it was to apply pressure and wait for it to open up. $52 part, an hour labor, and I'm good to go. Thanks, NGP!