At certain speeds or rpms, but mostly with no obvious connection to a certain speed or rpm
I am getting an evil high pitched whistle that sounds as if it's coming from under the dash.
When I press in on the brake pedal it goes away for a moment sometimes, sometimes goes away for several minutes. Also sometimes varying the load on the engine gets rid of it.
I am thinking there is a leak in the hose/fittings to the power brake booster that is exposed at only certain vacuum levels ?? Or the depth of the master cylinder piston- booster diaphragm uncovers a leak?
Only depressing the brake pedal immediatley gets rid of it for the short term.
Any experience with this ?
I'm thinking the sound is coming in thru missing grommets in the firewall.
