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Whine upon brake release

hey guys,

sometimes, usually cold and humid nights, when I release the brake from a stop, it lets out a long downward whine. A friend thought it was a vacuum leak and upon release the air goes in the hole and makes a noise when the humidity is just right.

I don’t know how else to describe it other than, back when it first started happening, I would look around and open the windows thinking it was a siren (just the downward part)

Any ideas?

Which “hole” are you referring to?

if there was a vacuum leak, then that would give a hole for air to go in?

maybe in the brake booster? i don’t know

There’s a vacuum check valve on the brake booster.

Since the problem occurs intermittently, I’d just replace it to see if fixes the problem.

They’re not that expensive.


I’ve had parking brakes do that, but never the regular brakes. For your problem, I think something w/the brake power booster is an excellent place to start. The hose between the intake manifold and the booster could be partially plugged with gunk, the connections on either end of the hose could be getting loose, the hose could be collapsing, the check valve as Tester mentions above, or the diaphragm inside the booster could be leaking. If you connect a hand held vacuum pump to the booster, does it hold vacuum to 20 inches hg?

hmm okay, i’ll look into it over the next weeks

How cold, @jjustinmbirchb? If below 32* you may have ice accumulating on the vacuum vent valve. But regardless of the temperature and ice the vent valve is a likely cause for the whine.

haha I’m in San Diego, so our cold is about 55 degrees :stuck_out_tongue:

but I guess that rules out super cold temperatures? I would guess it’s the humidity