need help with non g body project brakes.

[cut123]

I recently purchased and 84 buick estate wagon. Car had been setting since 1993. It had 3 bad place in rear brake line and one bad wheel cylinder. I replaced all brake lines and wheel cylinder. I also replaced master cylinder. First master cylinder was bad (cheap chinese from auto zone). second master seemed fine but when i turned on car brakes went away(pedal sinks all the way to floor slowly. Went to autozone got another and new valve for brake booster. Problem is the same again. Went to orielys and got a different brand of master , still pedal sinks. I have probably run 2 gallons worth of fluid through these lines but just in case i bought a pheonix reverse bleeder. Still same problem.

list of things done
1. new line
2. 3 news masters all bench bleed
3. fixed leaking wheel cylinder
4. can find no leaks
5. vacuum is good to booster
6. brakes get good pressure at all 4 wheels
7. regular bleed and reverse bleed seems like a hundred times.

 

[t01blaze]

You did bench bleed the new master cylinder. I missed that the first time I read it, whoops.
How about the brake booster itself? Usually it make the pedal hard not soft. The pedal should be hard if you pump the brakes with thre engine off, then hold the brakes and start the engine. The pedal should drop only a bit.

 

[Pontiac455]

Check to see if the e- brake is stuck on, this will give ya a low pedal. Also make sure the shoes are adjusted up good. If all is well there has to be a leak somewhere. The way I check the master is, remove the lines and put a nail in the line then screw tha lines back on. Pump the brakes and if the master is good tha pedal shouldnt mover much, should be hard as a rock.

 

[ssbrewskyaz]

I'm guessing that after you do all the bleeding and button everything back up, stand on the pedal, it goes to the floor, you recheck the master cylinder reservoir and it has the same amount of brake fluid as when you started correct?

In my opinion the first thing to determine is if there is or isn't a leak. If the pedal goes to the floor and the brake fluid level in the master is unchanged, it's a pretty safe bet there's no leak. Next is to determine where the fluid is bypassing to.

As someone else pointed out, the rear shoes should be adjusted out far enough so they just drag a little when you spin the drum(s) by hand.

Have you had a helper apply the brakes and someone actually go to all the wheel corners to determine if there's hydraulic pressure enough to hold the wheels from turning?

Did the master you purchased have an adjustable rod?

Is the proportioning valve all rusted to snot?

It's possible for brake fluid to leak back into the booster if the master has a bad rear seal or if the rod is too long and you're pushing through too far. The seal shouldn't be bad on a rebuilt master but stranger things have happened. Doubt it would happen three times though. That or you're one of the unluckiest guys on the planet.

Here's one last thought, not sure how far apart you had the brake system but the bleeders must be on the top of the wheel cylinder or caliper. If they're not on top, you'll never get it bled.

Scott, ...

:arrow: :arrow: :arrow: :wink:

 

[cut123]

Bleeders are on top. I will plug master tomarow to see if it holds firm. If its a leak it would have to be tiny. The rear drums have slight drag about where they should be I will check emergency brake but Im pretty sure its not on. I really dont wanna pull the booster if its not the problem. the car is huge with a lot of brake line so leak is still a possibility.

 

[cut123]

Update today. Plugged master had a solid pedal so i know the master is good. Ran 32oz of brake fluid through every line , reverse bleed with someone watching master cylinder for air. got next to no air out of any of them. Still no brakes . I have a brick on pedal now to try to look for a leak again. Intersting side note helper did say fluid came out of both side of master when i was bleeding rear drive brake.

 

[cut123]

looks like im gonna have to swap the engine on this. anyone know of any headers that fit? Im gonna stay with a sbo.

 

[pontiacgp]

Update today. Plugged master had a solid pedal so i know the master is good. Ran 32oz of brake fluid through every line , reverse bleed with someone watching master cylinder for air. got next to no air out of any of them. Still no brakes . I have a brick on pedal now to try to look for a leak again. Intersting side note helper did say fluid came out of both side of master when i was bleeding rear drive brake.

make sure the proportional valve does need to be reset...