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Brake noise

I have a 1994 Mercury Villager van with 190k miles. When I hit the brakes firmly, I get a high-pitched whistling noise–not really a squeak–for a second or two. It seems to be coming from near the pedal, not the wheels. It’s getting a little more frequent. I had a full brake job 10k miles ago, but the noise didn’t start until a few months back. Any ideas?

The noise might be coming from the diaphram inside the vacuum brake booster or the check valve for the brake booster. If you can get it to make the whistling noise while sitting and idling, pinch off the vacuum hose to the brake booster. If the whistling stops, the problem is in the brake booster area.

Tester

Thanks for the quick help. How would you rate this as a safety issue?

It’s only a safety issue in that if the leak becomes worse it could affect the function of the brake booster in assisting you annd the brakes could require more force to apply…in a sudden unexpected event it could mean the difference between being able to stop and crashing.

The booster only assists you in applying force. It’s failure would not render the brakes inoperable…just harder to apply.