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Neal, Chevy Mechanic
Category: Chevy
Satisfied Customers: 8349
Experience:  Shop Owner and Mechanic on multiple makes.
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2001 chevy impala: warmed up and I depress the brake stalls

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I have a 2001 chevy impala 3.4 engine. once it's warmed up and I depress the brake pedal rapidly, the car stalls. When the engine is still cold this doesn't occur. I've checked for vacuum leaks and found none. What could be causing this?

I'm Neal and I am here to assist you. Only accept when you are happy with my assistance. If I can't help I will open your Question to other experts.


If there is a leak in the brake booster, or the vacuum hose or a cracked, ruptured or leaking diaphragm it can cause a stall. It may only be leaking when the pedal is depressed.


Is it running well? If it is not running good it will not make as much vacuum and hitting the brakes will use up all the available vacuum and stall the engine.

Customer: replied 4 years ago.
It's running well and the hoses all look good. So maybe it must be the diapram. How would I check that exactly.

Shut the engine off and immediately pull the one-way valve off the booster. If the booster is holding vacuum, you will hear a loud whooshing noise.

If no noise or very little is heard, check the one-way valve to see if it is functioning properly. Hold the valve to your mouth and put suction on one side and then on the other. If air can be sucked through the valve in one direction and not the other the valve is good. If air can be sucked through both sides it is bad and needs to be replaced.

If the valve is good then the booster is bad and needs to be replaced. The reason for the failure could be it is defective or it could have a leaky master cylinder. Look at the mounting surfaces where the master cylinder mounts to the booster. If there is any brake fluid on the booster the master is leaking into the booster and causing deterioration of the diaphragm. Replace the master cylinder as well, for it will ruin the new booster.

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