brakes, master cylinder, I am frustrated!!

Discussion in 'Trucks and Trailers' started by sailinstud420, Sep 25, 2006.

  1. sailinstud420

    sailinstud420 LawnSite Senior Member
    Posts: 343

    I am trying to get the brakes working good again on my '89 chevy k1500. I have gone through two autozone master cylinders now along with one napa one (re-man'd) and the pedal is still going to the floor. My dad made the mistake tonight of pushing the MC all the way in when bench bleeding it, which the instructions say not to do. (I didn't do that on the first two!!) My question is why not? I measured the distance the pedal pushes it in and that is the exact same as how far it is possible to push it in when its on the bench, so what gives? I wonder if that is the problem with my reman'd napa this time around? The only thing I can think of is when you push it all the way in the seals are getting torn up, is there any insight into my problem? I bled the heck out of the lines and its not leaking fluid, whats the problem?
     
  2. Lovbcstiller

    Lovbcstiller LawnSite Member
    Posts: 21

    Have you checked the Vaccum hoses that go to the brake booster? Also check the brake booster too.
     
  3. mojob

    mojob LawnSite Senior Member
    Posts: 515

    Come on guy what are the odds of having three bad replacement parts and how do you know the seals are getting torn up? Sounds like you might be in over your head. Get a real mechanic involved before you kill somebody.
     
  4. nobagger

    nobagger LawnSite Gold Member
    from Pa
    Posts: 3,065

    Did you bench bleed the master cylinder before you installed it? If so are the bleeders working on the calipers and rear wheel cylinders. If so it could be a brake booster or a proportioning valve gone bad. Braking systems are nothing to leave half a$$ed done especially towing a trailer. I would spend the money and take it somewhere if these do not fix it.
     
  5. sailinstud420

    sailinstud420 LawnSite Senior Member
    Posts: 343

    I am confident working on my truck myself, thank-you. I asked a simple question, and yes I bench bled the cylinder and I bled the lines, as my original post says. Maybe if some of you would work on your own stuff once in a while instead of bringing it in you would be able to answer my question rather than tell me I am in over my head. You have never seen faulty parts come out of Auto zone before? Keep going there and you will. I have talked with several mech's the last few days that say they have gone through 6 or 7 MC's from A-zone without any success. thats why I switched to the Napa one, which I thought would solve it, but now that it got bled and pushed in all the way I am skeptical.

    Lovbcstiller - I am led to believe its not the brake booster because the pedal firms up like it should when the truck is not running. If it was a vaccuum issue/leaking the pedal wouldn't remain firm.

    The question is still the same, What happens if you bench bleed the MC and it gets pushed in too far? Will it wreck the seals?
     
  6. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613

    It should not wreck the seals because during the reman process they remove all seals, hone out the cylinder and reassemble with new parts. What ruins the seals is pressing the pedal to the floor on a old car/truck that normally never has had brake pedal past the 70% point, corrosion and rust forms at the area that is not constantly used and thus pushing the seals over this rusted area tears them up.

    I dont know what you problem is but my best guess is that you have a pocket of air somewhere that isnt being bled out.
     
  7. dwlah

    dwlah LawnSite Senior Member
    from Argo Al
    Posts: 558

    Sounds like an air bubble somewhere
    May want to try hooking a vacuum pump to the wheel cylinders and bleed them again
     
  8. Rickco

    Rickco LawnSite Member
    Posts: 135

    Have you relaced or moved any of the lines leaving the master cyl. if one is arched higher than the fluid level in the master you will have air traped that is almost imposible to get out.
     
  9. stumper1620

    stumper1620 LawnSite Bronze Member
    Posts: 1,889

    This is correct and I have never heard of not bench bleeding without pushing all the way in. how else can you get 100% of the air out and be sure about it?
    Sailinstud are you sure you don't have a bad vac booster? can you get a solid pedal when the truck is not running? or is this without the truck running?
    if you think all is ok in the booster, keep in mind that the rear brakes are what make the pedal solid, fronts only make it solid after the caliper pistons are pushed tight. Try to isolate the problem to the front or rear first, if the lines can be removed stick a plug in the rear and see if you can get a pedal, if not then the problem is in the front.
    If you have a compressor, I have a vac. bleeder that I could bring around and help you with it. PM me if you want any help.
     
  10. Rickco

    Rickco LawnSite Member
    Posts: 135

    Have you relaced or moved any of the lines leaving the master cyl. if one is arched higher than the fluid level in the master you will have air traped that is almost imposible to get out
     

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