Q: Squealing coming from brake power booster/check valve?

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When brake pedal is depressed i hear a squealing sound coming from area of Power Brake Booster. It doesn't sound like a mechanical sound. It's more like hissing leaking noise. Like a vacuum leak.

I'm not losing any Fluids from the master cylinder. The brakes also appear to be dragging like a warped brake disc, but i had the disc replaced and machined buy a mechanic.

My car has 134000 miles.
My car has an automatic transmission.

Hello - your problem sounds like a failed vacuum or fresh air valve in the power brake booster, or possibly a ruptured diaphragm in the booster. And, you are correct that this failure will not lose brake fluid. I would recommend having a Brake Vacuum Booster Replacement Service completed by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem, get an accurate assessment of damage and cost estimate for repairs.

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