Thread: Brake Troubles
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Old 08-12-2016, 05:06 PM
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bellaCuba bellaCuba is offline
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Re: Brake Troubles

+1^ I agree with Stealthee.

RPM rise when pumping the brakes, while idling, is normal for Chevy & GMCs, at least.

1 test you could do (even better if you know your vehicle well):
Start with the engine OFF. Pump the brake pedal until firm. Also, (1) take note how many pumps it took for it to get firm.
Next, keep your foot on the brake pedal with good pressure, then start the vehicle. (2) Pedal should drop down slightly if booster is working.

1. Should have at least 2 pumps before getting a hard pedal. If not & hard after 1 or 2 pumps, booster is not holding vacuum. Booster is bad.

2.If pedal doesn't move, then booster is bad.

If in doubt you can always try replacing the check valve 1st (in engine compartment near Master Cylinder)... if you're still having issues & failed above tests, then it's likely needing a booster.

Good luck! Keep us posted on your findings!
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