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Stiff brake pedal

Tiny
CONAGHER
  • MEMBER
  • 1965 GMC C3500
  • V6
  • 2WD
  • MANUAL
  • 350,000 MILES
New master, rebuilt vacuum 2018, rebuilt wheel cylinders 2010. Brake pedal is stiff with zero travel.
Monday, November 5th, 2018 AT 1:37 PM

9 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon.

Do you have vacuum to the booster? Remove the hose and verify there is vacuum.

If you have a vacuum gauge, check the amount of vacuum to the booster.

Does the linkage move freely? Look under the dash and be sure the pedal and rods move freely.

Roy
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Monday, November 5th, 2018 AT 1:49 PM
Tiny
CONAGHER
  • MEMBER
  • 5 POSTS
Pedal travels freely while l bench bleed master, will not travel with brake line attached. I will check for vacuum.
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Monday, November 5th, 2018 AT 1:57 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Sounds like a plan. Keep us posted.
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Monday, November 5th, 2018 AT 2:16 PM
Tiny
CONAGHER
  • MEMBER
  • 5 POSTS
Vacuum at Hydro vac verified, seemed to be strong. Brake pedal travels when brake line disconnected. Clutch side of master is functioning as designed.
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Monday, November 5th, 2018 AT 3:18 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Sounds like you have an issue with the hydro-vac unit.

Clutch side of master is functioning as designed. Can you explain this?
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Monday, November 5th, 2018 AT 3:23 PM
Tiny
CONAGHER
  • MEMBER
  • 5 POSTS
Hydro Vac rebuilt and new master cylinder installed both in November 2018. Slave cylinder on clutch side of master working as designed. All four Wheel cylinders rebuilt in 2010.
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Monday, November 5th, 2018 AT 3:30 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
It sounds like you have an issue with one of the brake flex hoses. They can become clogged internally. Here is a video of how to replace the brake hoses:

https://youtu.be/xMS8Xy4Xz1U

Please run down this guide and report back.

Cheers, Ken
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+1
Thursday, November 8th, 2018 AT 12:05 PM
Tiny
CONAGHER
  • MEMBER
  • 5 POSTS
I fixed this issue yesterday suspecting the same thing, a clogged line. Pedal travels freely when brake line disconnected, stiff when line is connected. Pulled line between master and Hydro-Vac and discovered flex portion of line to be clogged.

Thanks for the help!
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Thursday, November 8th, 2018 AT 5:06 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help.

Cheers, Ken
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Friday, November 9th, 2018 AT 11:13 AM

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