Have a squeal or sound like a loud buzzer coming from brake booster system after 3-4 presses of brake, more so when cold. This sound is in addition to the normal hum of the booster motor. Majority of people with similar issues indicated to replace booster motor. Replaced motor w/a new unit; however, no change in the buzzing/squealing. So think that the issue may be pump, not sure.
Has anyone repaired &/or rebuilt a brake booster pump? Is there such thing as a rebuild kit for the pump? Can find used motor & pump, not just a working pump.
Below are links to recordings of the sound coming from brake booster system, both inside & under hood of truck.
4RNR1 - YouTube
4RNR3 - YouTube
Tks