Thread: Strange high pitched noise - may be brake related - 94 300 TDi

Driving back from a (unsuccessful) fishing trip on the weekend my 94 300 TDi started making a whistling noise, which sounded like it was coming from under the driver's side kick panel. The noise stopped when I braked and started again when I took my foot off the brake pedal. I stopped for a look, and so did the noise. Drove further and it started again. I pulled the cap of the brake reservoir and checked the connections etc. All looked OK, and the noise stopped for a bit then started again.


I don't know if it is some sort of alarm, or maybe an occasional vacuum leak.


Appreciate if someone can point me towards what I should check.


Cheers
KevG

Thanks for the tips guys.


I ended up replacing the non return valve in the brake booster. The rubber grommet looked pretty worn, so I suspect that it was letting a bit of air past causing the whistle.