# new master cylinder, rear brakes not working



## BlueMonkey (Jul 27, 2009)

The other night I cleaned out my brake lines (brake cleaner & compressed air), replaced the rubber hoses, and installed the new m/c. My '71 is non-power 4 wheel drums. After bleeding, the rear brakes are not working at all, even though fluid comes out of the bleeders. Any ideas? 

Couple things I should mention: this car has been sitting 20 years, hard lines look ok, I did not bench bleed the master, rear wheel cylinders look a little rusty even though everything else is new (well, 20 years new) and the rear wheel clyinders won't move the shoes even w/ the drums off & brake pedal pressed.

Could this be proportioning valve, or faulty m/c, or would pulling the m/c off & benchbleeding help????? I probably need to go ahead and replace rear wheel cylinders, but wouldn't they at least move the shoes even if they look rusty/bad?

I do plan a front disc conversion in the somewhat near future, but would like to get the car running/driving/stopping 1st...

Thanks!


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## Rukee (Feb 8, 2007)

If you are pumping fluid out the rear wheel cyls but they don't move the shoes, replace the rear wheel cyls. They are bad.


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## ride400 (Jun 16, 2009)

were the rear brakes working before you changed the master? replacing the wheel cylanders is a good idea. as well as bleeding the master before instalation, that is something that i always do before installing a new dry master cylander.


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## Three Deuces (Sep 22, 2009)

What they ^ said.


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## jetstang (Nov 5, 2008)

Keep bleeding them, there is probably still air in the master cylinder or up in the lines. I did mine last night and they didn't work for a long time, but fluid did come out the cylinders. Then, the air started burping out the lines and the peddle came up. Now, I have a full brake peddle, 1/2" of play up top! My brakes are great. I put a New AC Delco Master Cylinder and booster in, and it looks really good.


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## Too Many Projects (Nov 15, 2008)

Not bench bleeding the master was a major OOOPS. Doing it now won't help. All that air is in the system and needs to be purged thru bleeding. Always start bleeding at the position farthest from the master. That should've been the right rear. As has been said, there may still be air in the lines. You didn't say if the pedal was normal height or soft or fades. These would indicate different scenarios too. If the pedal is low, soft, fades, you still have air. If it is high and firm, the wheel cylinders are most likely stuck but with a hard push should move. Hydraulic pressure moves buildings, it should move a stuck piston. They may not retract and release but they should move.


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## 05GTO (Oct 6, 2004)

jetstang said:


> Keep bleeding them, there is probably still air in the master cylinder or up in the lines. I did mine last night and they didn't work for a long time, but fluid did come out the cylinders. Then, the air started burping out the lines and the peddle came up. Now, I have a full brake peddle, 1/2" of play up top! My brakes are great. I put a New AC Delco Master Cylinder and booster in, and it looks really good.


:agree


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## 68greengoat (Sep 15, 2005)

Rukee said:


> If you are pumping fluid out the rear wheel cyls but they don't move the shoes, replace the rear wheel cyls. They are bad.


:agree Being that the wheel cylinders are at least 20 years "new", I would still replace them just for insurance and peace of mind.... I replaced all mine. You can purchase them at your local auto parts dealer. They're not very expensive....


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