Brake pedal was very stiff

Tiny
JEREMY0507
  • MEMBER
  • 1995 GMC SIERRA
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
So my brake pedal was very stiff an my truck was barely stopping so I changed the brake booster. The issue has not changed. It is still hard and my engine idles higher when I push brake pedal which it did before also. Think I got a faulty booster or maybe another issue?
Tuesday, June 5th, 2018 AT 2:08 PM

6 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi and thanks for using 2CarPros.com. If it is doing the same thing, it does not sound like a booster problem. For the booster to operate properly, it needs eighteen inches of vacuum from the engine. Remove the vacuum hose to the booster and check if you are getting that. If you are not suspect there is a plug in the hose, a cracked hose, or another vacuum leak causing engine vacuum to drop.

Here are directions for checking engine vacuum and how to identify a leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Try this first and let me know what you find.

Take care,

Joe

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Wednesday, April 14th, 2021 AT 1:47 PM
Tiny
JEREMY0507
  • MEMBER
  • 27 POSTS
Will a vacuum leak cause the brake pedal to get very hard an not let the vehicle stop?
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Wednesday, April 14th, 2021 AT 1:47 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi again. The reason the pedal is normally easy to press is because of engine vacuum in the brake booster. If there is a leak, you may not get the assist. Hence, it is hard to press.
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Wednesday, April 14th, 2021 AT 1:47 PM
Tiny
JEREMY0507
  • MEMBER
  • 27 POSTS
I checked the vacuum hose going to the booster an it is still good. There is lots of vacuum. Would a bad ABS module cause this?
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Wednesday, April 14th, 2021 AT 1:47 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi, honestly the module would not cause this. Have you checked intake vacuum with a gauge to determine if it is adequate?
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Wednesday, April 14th, 2021 AT 1:47 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
After thought. Is there a white one way valve on the booster where the vacuum hose connects? If so, remove it and see if it is blocking vacuum.
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Wednesday, April 14th, 2021 AT 1:47 PM

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