No pressure to rear drums?

Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's, Olds 98 91-96, Buick Lesabres and Park Avenue 91-96. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.
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beater98se
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Year and Trim: 1998 SE

No pressure to rear drums?

Post by beater98se »

Hello everyone, first post here.

I bought a 98 SE about a month back. I knew it needed a brake line (Driver's front) and front pads and rotors (badly). I also ended up patching about 7 holes due to rust, lol. 236,000km for $600 :)

Every line had previously been replaced besides the two from the master to abs module, and obviously the drivers front that broke, so I went ahead and changed all 3, including pads and rotors in the front. I found that all the slider pins were in either bad shape or seized so I changed all 4. (this explains why the front brakes were in such bad shape). Anyways, I continues onto the bleeding process and found that I couldn't get any pressure from the RR wheel cylinder. Just a dribble if I was lucky. I found a kink in the small section of line after the flex hose to the cylinder so I went ahead and replaced that too. The master was run dry and was able to bench bleed a bunch of air out of it. I also bled the lines up the the abs block until fluid came shooting out, including the RR brake line at the block. All other wheels bleed normally, but both rear drums still do not have braking pressure (I'm able to spin the drums with the brakes on). I found a kink in the small section of line after the flex hose to the cylinder so I went ahead and replaced that too. Now, I'm getting fluid out of the RR, but not enough to say that there's proper pressure (pedal has gotten harder but doesn't stay solid). I did a bit of research and I'm thinking that the proportioning valve is possibly stuck closed, but I'm not 100% on that. The PO had both rear hubs done, along with new drum components, including wheel cylinders. There's no fluid coming out of the end caps either. Is there a way to reset the valves or must they be replaced?

Any input or previous experiences will be really appreciated. Thanks!
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Re: No pressure to rear drums?

Post by 96 SSEi »

Hi, welcome to the club! To my knowledge, the valve will have to be replaced if its restricting too much. You can try removing the valve and run a line directly to affected wheel, if you get nice pedal pressure, the valve is the culprit- replace it......
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Re: No pressure to rear drums?

Post by MattStrike »

It is possible that rust has clogged the valves. They can be disassembled and rebuilt, but if they are the aluminum valves and are too oxidized it's not worth trying to fix them, just replace them.

It's just as likely that the abs module is clogged, so make sure you check that as well.
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Re: No pressure to rear drums?

Post by MKMike »

Given that there was rust in the system, are you sure there is no pressure to the cylinders and that it is not just clogged bleeder valves?
I'd fully remove the bleeder and reinstall it after each air release.
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beater98se
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Re: No pressure to rear drums?

Post by beater98se »

So all I did was tap on the valve a few times with a hammer, and voila, fluid under pressure. I still think theres a bit of air in the system still but I now have acceptable braking pressure. Hopefully I wont run into valve issues down the road :/ Thanks everyone
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