[Vwdiesel] 85 Jetta TD Air Filter Noise FIXED

Doyt W. Echelberger doyt at buckeye-express.com
Wed Apr 26 18:29:06 EDT 2006

Rejoice with me. The conversation-stopping rattle from the air filter box 
is FIXED! The noise puzzled me for at least 10 years and I could only stop 
it by taking off the lid of the air filter box and removing the air filter. 
Without the filter or the lid, the noise was gone. I couldn't run that way, 
so I just ignored the noise and accepted it as a characteristic of driving 
this wonderful car.

Big mistake. Should have looked deeper into the system of how intake air is 
ducted from inside the passenger front fender into the air filter box. 
Maybe some of you are living with the same problem.

After adjusting the solid valve lifters today, I was leaning on the 
passenger fender, listening to the engine idle and looking for valve cover 
leaks, when I noticed that the rattle seemed more associated with the 
fender than the air box. I ran my fingers down the inside of the fender, to 
the point where the tube from the air filter entered the fender. The plate 
on the fender that sealed this union was vibrating as though a tiny hammer 
was inside, pounding away.

I twisted the tube where it entered the fender, and was able to get one 
finger inside the fender. I felt a plastic plate about 4 x 4 inches, and it 
was being sucked up against the entry tube like a flapper, making the 
racket.  AHAH !! Ten years of mystery about to unravel.

The tube went into a plastic box that was located inside the fender. It 
was  sort of like a rectangular box that electricians use to protect 
junctions. The curbside wall of the box had come loose from the walls that 
were designed to hold it away from the entry tube, and it was trying to get 
into the air filter and participate in the combustion process.

I took the system apart and spread the parts out on a towel, and decided to 
simply eliminate the offending plastic wall rather than trying to repair 
the "junction box." The noise is gone, and so is the back wall of the box 
in the fender. I'll probably take it apart in a few days and figure out how 
to restore the original integrity of the fender box, because it certainly 
has something to do with keeping water out of the intake. But for now, THE 

So I rejoice....with some embarrassment at having put up with it for ten 
years.  It probably also cut down my engine efficiency. ....considerably. I 
thought the engine was just getting old.  Pictures of the offending plastic 
plate and the entry tube that goes into the fender are available on 
request. If a web site could display them, it might help somebody.

Doyt Echelberger
85 Jetta TD.................. now quieter

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