Moaning sound AFTER the brake pedal is released. 2015 VW Tiguan

Question

I am recently experiencing a weird noise coming from the front brakes (I suspect the passenger side). It only happens AFTER I remove my foot from the brake pedal. The noise would come up after around 0.5 second after full releasing. The moaning noise last about 0.5-1.5 seconds, and this peculiar noise does not come up all the time. It happens once out of about 4-5 times, rather irregular. It happens both at full stop and at slow speed deceleration, never at a high speed deceleration.

The vehicle is a 2015 VW tiguan AWD, I had a small incident on the passenger side door 2 years ago, but the noise only came up 3 months ago. Any one has any ideas?

Thanks!!

Answer 1

My first suspects would be either the brake caliper guide pins, the caliper pistons, or the pads themselves binding up as you apply the brakes and then slowly releasing as you let off the brakes.

It's likely causing uneven wear on your brake components and may be leading to an unsafe condition in your brakes.

My recommendation would be to service the brakes as soon as possible.

Answer 2

One thing that happens when you release the brake pedal is that the vacuum in the brake booster's reservoir is restored by the engine vacuum. If the inline check valve is worn, it can make a moaning sound. If the diaphragm is fractured, it usually makes a hissing sound.

Turn off the engine and pump the brakes repeatedly until the brake pedal is hard and you have no more brake boost. Release. Now press the brake pedal hard and release it (engine still off), listening carefully for the moaning sound. If you don't get one, the sound is probably related to the brake booster.