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#1 |
Senior Member
Join Date: Aug 2002
Location: Plymouth, MA
Posts: 891
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No Rear Brakes with lots of troubleshooting need help!!
OK, I was driving my truck the last 2 weeks as my daily driver. I was suspect of my rear brakes and finally jacked it up this weekend to see if they were working and they weren't. First I tried the obvious and rebled all 4 brakes, with neg results. Then, I used CPP and some comments from the board and tried to reset the combination valve, still no rear brakes. At this point, I am not sure what else to try another than a new master cylinder. Attached below is a photo of my current setup. Is it the right one for disc front and drum rear? Thanx for any help.
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1972 Blazer body...need to get a thread started for the rest of the story Last edited by NPilot1975; 03-18-2007 at 10:04 PM. |
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#2 |
Active Member
Join Date: Apr 2005
Location: Miami, Florida
Posts: 286
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Re: No Rear Brakes with lots of troubleshooting need help!!
With disc all around you can ditch the combination valve but you will need to add and use a proporting valve for front/rear bias adjustment...
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#3 |
Senior Member
Join Date: Aug 2002
Location: Plymouth, MA
Posts: 891
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Re: No Rear Brakes with lots of troubleshooting need help!!
Is there a way tell if the MC is good without taking it off? I had the lid off, if the brakes were pumped there was a jet of fluid that would come up in each bowl (not out of the bowl but above the surface of the fluid.) I was told this is not good. I get fluid at all four corners, but the front discs work and the rear drums have nothing. I am assuming MC or Combo Valve????
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1972 Blazer body...need to get a thread started for the rest of the story Last edited by NPilot1975; 03-19-2007 at 10:14 AM. |
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#4 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: No Rear Brakes with lots of troubleshooting need help!!
I would suggest taking the line to the rear off of the prop valve and try bleeding it there first. If no fluid comes through it is the prop valve or the MC.
To eliminate the prop valveas a problem bleed the rear of the MC only. All of the Master Cylinders that I have seen have the fluid stream up when depressing the brake pedal. Sometimes bleeding the rear brakes can take forever so if the MC and prop valve check out, just keep bleeding the rear. Jim
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1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#5 |
Registered User
Join Date: Aug 2006
Location: Bakersfield,CA
Posts: 7,893
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Re: No Rear Brakes with lots of troubleshooting need help!!
one another thing to think about is the wheel cylenders
goodluck
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-steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME |
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#6 |
I am a Referee of life.
Join Date: Jun 2000
Location: Greensboro N.C.
Posts: 13,993
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Re: No Rear Brakes with lots of troubleshooting need help!!
If you don't have a good stream of brake fluid at the rear wheels(if it dribbles rather than squirts) You could have a collapsed hose on the rear.You may still get some fluid but it may not be enough to actuate the shoes.
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The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil" |
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#7 |
Registered User
Join Date: Mar 2001
Location: RADFORD, VA
Posts: 2,651
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Re: No Rear Brakes with lots of troubleshooting need help!!
Check the rear end rubber line (on the differential) if it's old and drie rotted it will collaps and thus no fluid,will pass through.Hope this helps.
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#8 |
Registered User
Join Date: Mar 2001
Location: RADFORD, VA
Posts: 2,651
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Re: No Rear Brakes with lots of troubleshooting need help!!
Oops,Paneldeland beat me to it,wouldn't hurt to check.
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#9 |
Who's got steelies?
![]() Join Date: Feb 2006
Location: Morrison, Oklahoma
Posts: 1,026
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Re: No Rear Brakes with lots of troubleshooting need help!!
When I did my rears I didn't just bleed them, I used one of those mityvac pumps and actually flushed all the old fluid and lines out. It took several refills of the master cylinder before the fluid didn't come out black and full of stuff: a good reason for changing the hoses- they rot from the inside too, and they are 30+ years old.
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#10 |
Senior Member
Join Date: Aug 2002
Location: Plymouth, MA
Posts: 891
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Re: No Rear Brakes with lots of troubleshooting need help!!
Thanx for all the comments. I may try to bleed the back again, although it seems to have pretty good stream when bleeding. I completely rebuilt the rear brakes 5000 miles ago and they look like they haven't been working at all. The shoes still look new. The combo valve is tripped and I can't get it to center, could that indicate a MC problem?
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1972 Blazer body...need to get a thread started for the rest of the story |
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#11 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: No Rear Brakes with lots of troubleshooting need help!!
Are you saying that you cannot get fluid past the prop valve?
If the valve is tripped and you cannot center it, there may be a leak in the rear. If it is tripped, you can usually get fluid by if you pump the brakes very lightly. Power bleeding as mentioned is a very good way to go. Jim
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1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#12 |
Black 72 Chevy
Join Date: May 2002
Location: Los Angeles, California
Posts: 662
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Re: No Rear Brakes with lots of troubleshooting need help!!
NPilot1975
I recently fixed my truck's brake problems and it was similiar like yours. My front brakes would lock easily and the rears would not assist. It turned out to be my prop valve was stuck.
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72 Chevy, SWB, 350engine, TH400 |
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