My 2003 s60 NA is starting to whistle when you let off of the brake pedal. The Vacum pump runs after you turn it off for a few pulses.
The brakes work fine and no CEL. I assume it will get worse. Do I need both or just the vacum pump?
no chance it can be an adjustment?
...michael
03 s60 vacum assist pump/brakes
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jimmy57
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didn't see this one 3 years back. The booster is why it would hiss. The leaking is why the pump runs. No need for pump unless it dies from too much running when booster leaks. Booster has equal vacuum front and back of diaphragm(s) when pedal released. When you depress pedal the first thing that happens is the backside vac is shut off and then further push bleeds out vacuum which lets pressure build towards or to atmospheric for the level of assist that matches your level of pedal apply force. If the regulator valve on back of booster (pedal pushrod goes to this) fails then it leaks vacuum. If the leak is bad it will self apply brakes with no foot on pedal. Usually just enough to drag brakes and make them smoking hot in a few miles
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