Drum Brakes Not Bleeding

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trailforyou

Not-quite-so-new-guy
May 16, 2020
16
11
3
Mesa, AZ
Brake light came on and pedal went all the way to the floor a couple days ago on my 1980 Buick Regal. Went ahead and got a new master cylinder to install. Followed a YouTube video and did a bench bleed on it before installing, seems like I followed everything correctly but after installing and trying to bleed the rear drums, no fluid came out of them. Found a thread on here that it could be the proportioning valve and some kind of safety feature within that? Wondering if I should start there or if anyone has other advice.
Thanks
 

pontiacgp

blank
Mar 31, 2006
29,270
20,391
113
Kitchener, Ontario
push the button on the front of the proportional valve back in.... :popcorn:

are you sure you have no brake lines, flex line or wheel cylinders leaking
 
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trailforyou

Not-quite-so-new-guy
May 16, 2020
16
11
3
Mesa, AZ
push the button on the front of the proportional valve back in.... :popcorn:

are you sure you have no brake lines, flex line or wheel cylinders leaking

yes no leaks anywhere. Had some fluid come out when i opened the bleeder screw on one of the rear drums before installing the new MC but not much at all and still nothing when pumping the brakes.
I'll give that button a shot, thank you
 
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timo22

G-Body Guru
Sep 10, 2012
550
1,072
93
St. Louis,Mo
I had the same issue on my Bonneville. I replaced all the brake lines ,brake hoses, wheel cylinders and calipers. I could get the fronts to bleed but nothing out of the rear cylinders. The proportioning valve had no button to push, so I wasn't sure what to do. The brake warning light was on so I knew the valve was tripped. I googled it and some guys said to drive it and stomp the brakes. So I drove it forward and reverse hard and stomped the brakes. Nothing...Then I had to hang a three point u-turn and when I lightly hit the brakes, I heard a little click ( valve reset ) and the light went off. I was then able to bleed the rear cylinders.

timo22
 
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trailforyou

Not-quite-so-new-guy
May 16, 2020
16
11
3
Mesa, AZ
push the button on the front of the proportional valve back in.... :popcorn:

are you sure you have no brake lines, flex line or wheel cylinders leaking
Do I have to do anything else when I push the button? Like have the bleeders open or anything? Sorry this is all new to me lol
 

trailforyou

Not-quite-so-new-guy
May 16, 2020
16
11
3
Mesa, AZ
I had the same issue on my Bonneville. I replaced all the brake lines ,brake hoses, wheel cylinders and calipers. I could get the fronts to bleed but nothing out of the rear cylinders. The proportioning valve had no button to push, so I wasn't sure what to do. The brake warning light was on so I knew the valve was tripped. I googled it and some guys said to drive it and stomp the brakes. So I drove it forward and reverse hard and stomped the brakes. Nothing...Then I had to hang a three point u-turn and when I lightly hit the brakes, I heard a little click ( valve reset ) and the light went off. I was then able to bleed the rear cylinders.

timo22
havent checked the valve yet but if theres no button, i'll give this a shot. thank you
 

pontiacgp

blank
Mar 31, 2006
29,270
20,391
113
Kitchener, Ontario
mine had a button but it was stuck so I backed the car up and stomped on the brakes, did that 3 times and heard a click and it was reset. We had a 2nd gen Camaro we raced and that had a pin that would not stay in so we had to push the pin in while the rear brakes were bled and it was ok after that
 
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83StreetMachine

Master Mechanic
Dec 16, 2011
395
819
93
Central NJ
Sometimes if there is no button to push in, I give her a couple of taps with the ole Tanya Harding. Then do the reverse brake stand.

pr30.jpg
 
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mc1984ss

Master Mechanic
May 18, 2020
293
237
43
On a normally operating valve should you be able to pull it in and out?
 
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Oct 14, 2008
8,806
7,746
113
Melville,Saskatchewan
I actually had to use a pressure bleeder to get fluid to the rear of my 70S after new lines and a master cylinder. The valve was still in the proper position.
 
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