Master Cylinder

Tiny
LASURVIVOR47
  • MEMBER
  • 2003 GMC SONOMA
  • 4.3L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
I removed the master cylinder from my truck because it would not gravity feed the rear lines. Before removing it I disconnected the front port line on the master cylinder it was okay, but the rear port would not bleed. I figured air might be trap in the rear port. So I pulled it and bench bled it front and rear ports. All air was evacuated. Re installed master cylinder. I waited for quite awhile and there was still no fluid coming of the rear port on the master cylinder. Not able to do the rear brake bleed. Any suggestions? Thanks for your time!
Saturday, August 20th, 2016 AT 7:31 PM

10 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
You do not have ABS do you? Also have you tried traditional bleeding instead of gravity bleeding?
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Saturday, August 20th, 2016 AT 7:35 PM
Tiny
LASURVIVOR47
  • MEMBER
  • 45 POSTS
No ABS. I have not tried the two man braking. Thought I would try and do the complete gravity bleed, but could not get the rear port on the master cylinder to gravity bleed by itself.
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Saturday, August 20th, 2016 AT 8:52 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Try the two man I think you will have success with that. Let me know how you make out.
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Saturday, August 20th, 2016 AT 8:57 PM
Tiny
LASURVIVOR47
  • MEMBER
  • 45 POSTS
I will let you know. The line from the master cylinder to the proportion valve is dry. Might end up sucking air back into the master cylinder, but I can always re-bleed the master cylinder later. Thanks, I will get back to you.
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Sunday, August 21st, 2016 AT 7:19 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
If you have a air compressor what I like to use a air powered vacuum brake bleeder it works great.
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Sunday, August 21st, 2016 AT 7:53 AM
Tiny
LASURVIVOR47
  • MEMBER
  • 45 POSTS
Success! Thanks for your help. I used my MITYVAC vac/pressure kit to force fluid from the back wheel through to the Proportion valve to the master cylinder. Then I pumped the brake pedal to make sure brake fluid was being transferred from the master cylinder to the back wheels. I gravity bled the rears and it worked. From there I had someone pump the brake pedal for me as I bled the system. No leaks, great pressure! Much appreciate your advice and thanks again!
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Sunday, August 21st, 2016 AT 11:03 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Glad to hear it that is what we are hear for. Please tell all your friends about us.
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Sunday, August 21st, 2016 AT 1:25 PM
Tiny
LASURVIVOR47
  • MEMBER
  • 45 POSTS
Absolutely! Thank you!
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+1
Sunday, August 21st, 2016 AT 2:13 PM
Tiny
RENEE L
  • ADMIN
  • 1,260 POSTS
Please let us know what you find so it will help others.
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Tuesday, August 30th, 2016 AT 9:23 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
They did read above
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Tuesday, August 30th, 2016 AT 11:45 AM

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