bleeding brakes sucks - no pedal

Discussion in 'The whoa and the sway.' started by BuicksRock, Nov 5, 2005.

  1. BuicksRock

    BuicksRock Well-Known Member

    Hello all,

    I just spent 3 hours bleeding my brakes today after 2 hours of it yesterday and I still don't have a decent pedal, or much of one at all for that matter.

    These A-body brake systems are the hardest things to get air out of. I swapped from all drum to a disc/drum set-up. Master is new from Year One, as are the calipers, rubber lines and rotors. I have bench bled the master twice, gravity bled all four corners, I did the traditional 2-man method, and even went and bought a MityVac and used it. There is no more air coming out of the lines and all methods led to the same conclusion: No pedal. If I put the car in Neutral and slowly roll it, I can push the pedal all the way to the floor and it will just barely stop, I hate to think what would happen if I actually put the car in gear :Dou:

    I am not new to bleeding brakes, but I have never had so much trouble with any car I have owned. I think there is a big bubble in the proportioning valve, but I have no idea how to get it out. I tried having a buddy smash the pedal as hard as he could with first the rear passenger bleeder open then the rear driver's side bleeder open, but I still get the same spongy, no-pressure pedal. Any suggestions?

    -Chris
     
  2. sparkplug

    sparkplug Well-Known Member

    Hello, there is a place on the frame where all the lines come together..Oh yeh a manifold.. If you pressed down on the pedal to much when you replaced the master cylinder, you may have jared the insides of that manifold.. There is a spring and a piston in ther also..I am no mechanic but I believe you have to take that apart to fix it or get a new one.. Hope this helps.. Randy.
     
  3. BuicksRock

    BuicksRock Well-Known Member

    Randy,

    Are you talking about the proportioning valve? That is the box with four brake lines going into it. I swapped it in from a 72 skylark that had disc brakes. I don't see how that would cause no pressure in the pedal unless it has air in it as I mentioned in my first post.

    I know it has a rubber button that has a pin in it that has to be pushed when bleeding the front brakes. I have never heard of anyone rebuilding one of these, but at this point I would believe anything.

    Anyone else?

    -Chris
     
  4. sparkplug

    sparkplug Well-Known Member

    Thats it..The way I understand it is, The little piston in the perportioning valve.. gets sprung or something and its kind of a b*tch to fix it.. Maybe you can switch it back to the original one that is in there to see if that is the problem.. A mechanic friend told me of this problem.. It wasn't the problem I had.. But it could be yours.. My problem was the seal was bad in my booster cylinder and it was leaking into the manifold.. hence smoking engine and no brakes.. :Smarty: :Do No:
     
  5. GStage1

    GStage1 Always looking for parts!

    Randy,
    Let's see you went to new front disc set-up, correct?

    First, did you use the 70 disc valve set-up? It has a "hold off" valve that mounts to the master cylinder. There is a small relief/release pin in that hold-off. If it does not move, you need to replace it or go to the 71-up disc brake combo valve located on the frame rail.

    When bleeding, sounds like you have no fluid flowing to the rears. This has nothing to do with the hold-off valve and you should have fluid flowing. I would suggest putting the car on jack stands and removing all 4 tires.
    Open the rear bleeders and remove the rear brake line from the master cylinder. Use compressed air to do a flow check and see if your assistant can feel air blowing out the bleeders. If not, your brake hose that goes from the rear x-mbr to the top of the pumpkin is collapsed internally. Get a new one at Autozone for $20-25. Once you have that replaced, verify again with compressed air. Should work now. Reconnect to the master cylinder and have your assistant use the might vac on the either side with the other side closed. It should pull the fluid thru quickly. Repeat process for opposite rear side.

    For the fronts, remove the line from frt reservoir and open caliper bleeders, use compressed air again. You should have flow. If not, you have a bad hold-off, you can remove the line from it and use compressed air again to check for flow. If no flow, you have bad hoses.

    That is all there is to it. Don't assume anything! If your lines and hoses check out, you should have no problem bleeding brakes. Also, just because the master cylinder is new does not mean it can not be bad.
     
  6. sparkplug

    sparkplug Well-Known Member

    Sounds like your on the right track George.. I am not doing the conversion, that's Chris.. I am just trying to help.. like you.. Thankyou for your reply..
     
  7. BuicksRock

    BuicksRock Well-Known Member

    George,

    I may not have made myself completely clear. I am getting a good stream of brake fluid out of all four lines, including both rears. Before the swap to front discs, this car saw regular street use with the all drum set-up, so there are no collapsed lines.

    Yes, I am running front disc, rear drum set-up with a proportioning valve from a 72 skylark with disc brakes. After looking at the PV closer and pulling the rubber boot off the top of the pin, I saw that the pin was stuck in and would not come out. So, I have ordered a new PV from Year One and we will see what happens.

    -Chris
     
  8. GStage1

    GStage1 Always looking for parts!

    Ok, clear now.

    If that does not solve your problem, you new master cylinder is bad. Is it rebuilt/reman or new?????

    I had so many problems with rebuilt units, that I only buy new ones now from TRW/Raybestos.

    What sometimes happens with reman units, seals are bad and the master just moves fluid back and forth and never out the lines.
     
  9. Ken Warner

    Ken Warner Stand-up Philosopher

    2 things

    First thing to try... I just helped out a guy with a Chevelle this summer. He had a good stream of fluid at all 4 corners but the car just would not stop with any level of comfort. Pedal would sink to the floor and the car would slowly come to a stop. The problem was the operating rod between the master cylinder and the brake booster. He was trying to use the old "short" one from his drum-drum setup on his new drum-disc master cylinder. A visit to may basement and procurement of a longer style rod fixed the problem in about 5 minutes.

    Second thing to try... Re-bleed all 4 corners (DO NOT "PUMP UP THE PEDAL") if you don't know the proper way of bleeding brakes do a search on the forum as I and others have typed this up several times in the past. While you are bleeding this time though after your helper opens the bleeder FREAKIN' JAM the brake pedal to the floor instead of the gentle push you should normally use. I've seen a lot of these systems get an air bubble stuck in the prop/hold off valve and it just would not move along without some abuse. I know some people are hung up on the rubber button thing on the prop/hold off valve but I've never seen it make any difference when pushing it. I have seen my "JAM the pedal" method clear up issues several times.

    As usual your mileage may vary. Whatever happens though let us know what you did to fix the problem... So often 10 people make a suggestion, and the problem gets solved BUTwe never find out what worked because now that the problem is gone the problem-ee no longer wants to talk. We need feedback on problems in order to actually learn what works and what doesn't!!!!

    regards
     
  10. tlivingd

    tlivingd BIG BLOCK, THE ANTI PRIUS

    i had this problem with I did the disc brake converstion and new brake lines and a reman MC after the new MC didnt even bench bleed properly. i finally got fluid to the rear but barely any fluid movement. I even used a mighty vac and it held 20 inches of mercury at a vacuum. I had enough pedal to stop so i only drove it in the VERY early morning when nobody was out and had a shop do a power bleed on it. best 70 bucks i've ever spent. I now have a rock hard pedal.

    something else to check if the front seem to be bleading fine but the rear is giving you problems is your flex line to the rear may be bad and has a crack inside the hose acting as a valve.

    -nate
     
  11. gun-G

    gun-G Long time Buick Nut

    Try tapping the wheel cylinders or caliper before opening up the bleeder valve with a ballpeen hammer...gets all the little bubbles to join together. Also, I notice with a Mighty-Vac, I spend less tiome if I keep some thumb pressure on the cap of the waste reservoir. Steve
     
  12. Ken Warner

    Ken Warner Stand-up Philosopher

    so what happened?

    :Do No:

    sending p.m.
     
  13. BuicksRock

    BuicksRock Well-Known Member

    Come on Ken, I am not a professional mechanic, I have to go to my paying job through the week. That, on top of keeping track of three kids only allows me to work on the Buick on Saturdays (and not all Saturdays at that). Give me a chance, I will post a follow-up.

    -Chris
     
  14. Russ Waters

    Russ Waters Well-Known Member

    Been there before... When I did my conversion I replaced everything, but could not get a decent pedal. After many ideas were tried and 2 new NAPA master cylinders, it turns out the DOT-5 silicon fluid was the culprit. :blast:
    I wasted a lot of time and money on that stuff, but when I changed back to DOT-4 fluid ( and another MC) all of my troubles went away. Now I have great brakes.
    It seems the seals in the master cylinders from NAPA were not compatible with DOT-5 fluid. Just another angle to help you in solving this.

    Russ Waters
    1970 Skylark Convertible 455
     
  15. Truzi

    Truzi Perpetual Student

    I had a similar problem once on my Skylark, and ended up running the engine while bleeding the brakes. For some odd reason, I was able to get a good bleed that way. Any other car I've done has worked fine the traditional way.
     
  16. Ray

    Ray Well-Known Member

    Are You Sure Your Rear Brakes Are Adjusted Properly, I Just Put A Rearend In My Car, I Blead Rear Brakes And Pedal Sucked. Then I Adjusted The Rear Shoes Until I Could Barely Get Drum On And What Do Yah Know, I Have A Great Pedal.make Sure Your Rear Brakes Are Adjusted. That Is Where You Get Your Pedal From.see Yah Ray
    ________
    The Cigar Boss
     
    Last edited: Apr 15, 2011
  17. BuicksRock

    BuicksRock Well-Known Member

    Ray,

    This was a regularly driven car before the disc brake swap. The drum brakes felt good and stopped as well as drum brakes can. I have done nothing to the rear drums, so they should be set the same as they were before. I plan to check them out though. I am planning to dive in today and see if I can figure this thing out once and for all. I will let you all know how it goes.

    -Chris
     
  18. alec296

    alec296 i need another buick

    if pedal hard in engine isnt running?
    do you have the drum master still?try that one ,its not right for disc/drum
    but will work temp to find your problem if it is master
    you might have a bad master
    i have had that with replacement masters at work on all types of
    vehicles. once and a while a new one can not be made right.
    its like a light bulb you replace then turn it on and it blows right after.
    andy
     
  19. BuicksRock

    BuicksRock Well-Known Member

    Here's the big update:

    I still have no brake pedal. This morning I swapped out the old proportioning valve for the new one. It went pretty smoothly.

    I then went to the rear brakes and pulled off the drums (after a small war with the driver's side one). Driver's side shoes were out as far as they would go while still allowing me to put the drum on. The passenger side was way off. I found that someone reassembled the automatic adjustor arm wrong so I fixed it and adjusted the shoes as far out as they would allow for me to put the drum on.

    Next I pulled the master cylinder and bench bled it. I used both the Mity Vac and the traditional pushing-the-rod in method. I found that keeping it level did not get all the air out. If you rock it forward and back while vacuum pumping it gets more air out.

    I put the master back on and used the Mity Vac to bleed at all four corners until I got a good stream of fluid from all sides. I used the traditional method of bleeding next and had a partner slowly push the pedal while I opened and closed each bleeder screw starting from the passenger rear, then the driver rear, then the passenger front and last the driver's front. We did the full cycle three times and got a few more air bubbles out this way. I also tapped on the slave cylinders/calipers each time as someone suggested.

    I felt the pedal and it felt the same as it did last week, with the car running it goes straight to the floor and does not in any way stop the car. I then tried bleeding all corners using the mash-the-pedal-as-hard-and-fast-as-you-can technique and this actually got a little more air out.

    Pedal is still the same. Straight to the floor, not much effect on actually stopping the car. That is where I stopped.

    I did check a few things that people had mentioned. I have the donor car I got the spindles and stuff from on my property still so I took the master and booster off it and measured against a drum brake booster to see if the rods are different lengths. These two were the same length. Some people have mentioned swapping rods, but I know the donor car brakes worked well before it was parked and it used the same disc brake set-up as mine. Also, I don't see how you just swap rods. It looks like you have to disassemble the booster.

    So, I think either the new master YearOne sent me is a dud (which would surprise me) or there is a big air bubble or two in the proportioning valve or somewhere else in the system (which would also surprise me given the amount of bleeding that I have done).

    I am now considering having it towed to a shop to have them power/pressure bleed the system because I am tired of wasting my time and just want to drive before it gets too cold to enjoy.

    Anyone know how much air it actually takes to cause the pedal to go to the floor? I would think it would be quite a bit.

    Sorry for the long post, anyone have any more suggestions before I do this?

    -Chris
     
  20. Kirk

    Kirk Well-Known Member

    I had a master cylinder go bad on me rather suddenly. I think one (or both) of the rubber pistons had worn out. If I pressed the pedal normally, it would sink right to the floor. However, if I stabbed the pedal quickly it would build up pressure. I could then modulate the pedal as needed. Once I released the pedal the pressure went away again.

    I suspect (in my case) that the lips of the rubber pistons wouldn't make good contact with the cylinder wall unless a lot of pressure was present. During normal pedal application the fluid would slip past the pistions. But a rapid pedal would cause the seals to expand against the wall. Then, so long as I kept my foot on the pedal some amount, the seals stayed tight and I could brake normally.

    A new master cylinder solved the problem.

    In your case, I suppose you could test the master cylinder by temporarily putting pipe plugs(?) or similar stopper in place of the front and rear brake lines and then pressing on the pedal. If the pedal is now firm, then you know you're building pressure and the master cylinder is good. If the pedal goes to the floor, then it's leaking internally.
     

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