VW TDI forum, Audi, Porsche, and Chevy Cruze Diesel forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
I have a 2002 Golf TDI which I believe has a boost leak. It only happens on acceleration so I can't track it down while in the driveway. I have a recording of it here.

Anyways, I found the Checking for boost leaks article here and I wanted to attempt the procedure. I hesitate because I only have a rinky-dink oilless compressor, which can produce moist air. Would potentially moist air be dangerous to introduce into the intake? Thanks.
 

·
Premium Member
Joined
·
482 Posts
It's hard to tell where the sound is coming from but it doesn't sound like turbo spool. I can also hear wind noise.

I don't see how moist air is bad when you're doing a boost leak check. Obviously, if you're painting your car you want an air dryer on the line but the intake gets more moist air when you're driving in the rain.

Your other video

http://www.youtube.com/watch?v=icvTdxaHn1Y&feature=related

sounds an exhaust leak. A boost leak check won't find an exhaust leak, try looking at the exhaust, downpipe, etc., and EGR piping and check for black streaks. The comment that you just cleaned the intake makes me think that the EGR system has a leak somewhere. Of course, some intake gasket could be off too so check for both.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
The wind noise is an artifact of using a mic resting just below the wipers to record the noise. :) Inside the cabin I couldn't a decent recording.

Re: the moist air, I guess I was concerned since I would be putting air in past the air filter, which might remove moisture? I dunno, hence why I asked.

Re: my other video: That's old, resolved problem, but you nailed it. I had forgotten to tighten some bolts underneath the EGR. I'm actually impressed that you could hear any difference, since they sound similar to me.
 

·
Super Moderator
Joined
·
23,902 Posts
Yea, such a small amount of moisture is no factor.

A boost leak sounds more like air hissing that gets worse with boost, an exhaust leak is more scattered, it's more of a rapid staccato. The reason why is because the air being put out by the turbo is being chopped into tiny rapid pieces, the air being put out by the engine is the sound of combustion and from each individual cylinder.

Listen to a nonturbo motorcycle or car with no exhaust. That's the sound of combustion and it sounds like azz, IMHO. A quality muffler "tunes" the sound to a more exotic note instead of just making loud noise. A turbo car muffles the sound quite a bit too.

Your sound could also be a tensioner bearing , try driving at moderate speeds and making hard turns (within reason of course), it could be a wheel bearing if it sounds growling in side-side turns.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #5
Just a followup question. From the article:

Remove a vacuum tube somewhere along the intake.
Would either the vacuum tube going to the EGR diaphragm or the one going to the Anti-Shuddler valve suffice? I guess it isn't clear to me. I'm a n00b at this car stuff. Thanks.
 

·
Premium Member
Joined
·
482 Posts
Doubtful that the turbo is bad. After listening to the clip, it could be an exhaust leak, but not pre-manifold. That would sound more like the older clip that was an EGR leak.

Maybe there's a hole rusted in the exhaust and it is letting you hear the turbo spool up more. If there's a hole pre-cat, you can hear the turbo a lot more. Is exhaust noise the same or is it just during acceleration?

It doesn't sound like a belt or loose tensioner. Maybe a bearing or a boost leak.
 

·
Registered
Joined
·
5 Posts
Is exhaust noise the same or is it just during acceleration?
It's only during acceleration. I can drive < 15mph without making the noise. I have not mentioned that my acceleration curve had been affected; it takes alot longer to get to speed. The noise seems definately linked, for example accelerating onto a freeway, the noise is present. When i get upto speed, the noise is little to none. Going up a hill the noise is very noticable.

I wasn't going to mention this either because I thought it unrelated, but the car does wobble somewhat as well. I figured it was just unbalanced tires, and been ignoring it focusing on the acceleration notice. But since you guys mentioned wheel bearings are a possibilty...
 

·
Premium Member
Joined
·
482 Posts
You may have heard that if you jack up the wheel and shake at 12 and 6 oclock and feel play, then the wheel bearing is bad.

This is true if the wheel is about to fall off, but you won't feel a bad wheel bearing to this degree if its still driveable unless you have a runout gauge. That's true for sealed bearings. If you can feel a "sandy bearing" feel when rotating the wheel when it's jacked up, then it could be a bearing.

Drive at slow speed, turn hard left, right. you should hear tire noise but if there's a growling that gets worse, then it could be a wheel bearing.

Check the MAF, there's a writeup in the FAQ section on how to do this. A small boost leak won't change power that much unless it's really bad and if you can hear it that loud than maybe it really is that bad.

The intercooler and turbo hoses can pop off too, you have to look under the car for this.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #10
I tried the "turning hard left then right" diagnostic; I didn't hear any obvious growling or noises other than the tires. I've had a MAF failure before, this isn't like that -- the acceleration was much worse and there was no noise. If I may reiterate my question about the boost leak diagnostic: Would either the vacuum tube going to the EGR diaphragm or the one going to the Anti-Shuddler valve suffice? I guess it isn't clear to me. Thanks.
 
1 - 10 of 10 Posts
Top