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Possible brake booster issue?

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  • Possible brake booster issue?

    Ok, this has been going on in my car for a long time and I never really cared to find out why but...

    1. While ago I bought my 85t brakes sucked, bled them did nothing. 2. bought an 88t, brakes worked great, swaped all the good stuff(entire rear end brakes ect.) to the 85 and all the 85 stuff to the 88. Figured now my brakes should work good again. NOPE 3. Bled the crap out of the brakes putting 1.5 quarts through the MS. still suck. 4. replaced the master cylider with a new one and again bled the crap out of them, going from furthest from the MS to closest to the MS in that order. STILL SUCK.

    Oh by the way this whole time after I swapped the brakes (what I thought were crappy 85 brakes) to the 88 they now work fantastic. So the issue is in the 85.

    It could be 1 of 3 things. My first suspect is the brake booster is bad. Second would be the rubber lines. Third and least likley would be all of the hard lines.

    OH, there ar NO leaks ANYWHERE.

    Any other Ideas? Anyone ever heard of a booster going bad?
    85 Z31 6.0 LSX turbo 766whp/792wtq
    04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

  • #2
    I've been driving a car when the booster failed, nothing worse than going from power to no assist midway through the pedal travel. Have you replaced the master cylinder?

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    • #3
      Dweezil wrote: I've been driving a car when the booster failed, nothing worse than going from power to no assist midway through the pedal travel. Have you replaced the master cylinder?
      Yup number 4 on that list.

      The brakes still work good enough to use the car for street use but it just feels all wrong. Not like the way my first 84 turbo felt. Those brakes felt GREAT and they were stock! the 88T brakes should be even better than that! But nope, not until I fix the unknown problem.
      85 Z31 6.0 LSX turbo 766whp/792wtq
      04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

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      • #4
        Put a vaccumm pump to the booster maybe?

        Terrible idea putting those wheels on...

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        • #5
          I really don't recall who they where but on...aahhhheemmm...Z31... someone posted a thread about this over a year ago. (safe bet since I havent been there in that long )

          Sorry but I don't recall what exactly went wrong but this person had to replace the booster.

          I can say this from looking at my completely stripped down 84. Pulling off and installing a booster cant be a lot of fun.
          Just stand back and throw money.
          Performance costs money.
          Reliable performance costs more.

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          • #6
            I've had boosters go out before, and the only problem was the peddle
            became stiffer. It still stopped the same exept it requiered allot more
            effort to push the pedal.
            Is the pedal spongy? I would suspect the front brake lines are expanding.
            I would put the front on stands, pull the wheels and have a freind start
            it up and pump the brakes while I inspected the lines.
            imagination is a virtue

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            • #7
              craZed wrote: I've had boosters go out before, and the only problem was the peddle
              became stiffer. It still stopped the same exept it requiered allot more
              effort to push the pedal.
              Is the pedal spongy? I would suspect the front brake lines are expanding.
              I would put the front on stands, pull the wheels and have a freind start
              it up and pump the brakes while I inspected the lines.
              +1

              Terrible idea putting those wheels on...

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              • #8
                z

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                • #9
                  possibly spongy/worn rubber brake lines. it happened to my black 88T. I swaped them out to SS braided and the feeling was gone.
                  Gone - 1988 Shiro
                  2004 BMW 330Ci
                  2005 BMW 330i
                  1991 Twin Turbo Z's (Red and Black)
                  http://www.E46Turbo330Ci.com

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                  • #10
                    NIVO wrote: possibly spongy/worn rubber brake lines. it happened to my black 88T. I swaped them out to SS braided and the feeling was gone.
                    As a side note this can (and usually is) also be a worn master cylinder primary piston cup seals, or contaminated fluid in the mc.

                    Edit Additional Side note: After only 2 years of use fluid has absorbed an amazing amount of water in a so-called "sealed system". Enough to decrease its boiling point substantially... so I have flushed and replaced brake fluid every 2 years for safety reasons.

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                    • #11
                      I think I can grab some stainless lines off ebay for like 80 bucks or so. Maybe I'll do that, bleed the crap out of it and see if that takes care of it. If it doesnt well now i've got one more thing thats better than before :roll:

                      Man if its not the rubber lines then its gotta be the booster right? that would be the only thing left to replace. Unless there is some magical part I dont know about? :roll:
                      85 Z31 6.0 LSX turbo 766whp/792wtq
                      04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

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                      • #12
                        SS brake lines definitely wont hurt you. Make sure you get the 6 line set. I saw one a while back on e-bay that was only 4 lines. They were cheap but not what you actually want.

                        ( There are 4 rubber pieces in the rear, 2 on each side for those that don't know )

                        Have you already bypassed the clutch damper? If not then use one of those rear rubber lines you take off. Free and easy to do. :wink:

                        If the SS lines don't fix it then the only thing I can think of is that you have a bad booster. The hard lines are either good or leaking. The hard lines would be about the last thing I would suspect, especially if you have gotten eyeballs on all of them to make sure they aren't leaking or crushed somewhere.
                        Just stand back and throw money.
                        Performance costs money.
                        Reliable performance costs more.

                        Comment


                        • #13
                          I can almost garantee that your problem is the master. You either got a bad one, a good one went bad (it happens), or you did not bench bleed it properly. Get another, and if possible, spend the bucks on a new one.
                          Chuck Stong
                          300+ Parts and Performance owner
                          http://www.300-plus.com
                          2002 ZCOT president and always active member

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                          • #14
                            Firehawk wrote: I can almost garantee that your problem is the master. You either got a bad one, a good one went bad (it happens), or you did not bench bleed it properly. Get another, and if possible, spend the bucks on a new one.
                            Well, if this is the case, I'm gonna run the Z32 master cylinder. Maybe first I'll pull the current one out and bench bleed it, AGAIN. Thats the cheapest possible thing I can do for now being that its the hollidays and i'm like everyone else, Broke.
                            85 Z31 6.0 LSX turbo 766whp/792wtq
                            04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

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                            • #15
                              My brakes sucks!

                              Same crappy issue here. Bled all the calipers, still spongy. Rebuilt calipers and new seal kits, still spongy. No leaks. Maybe would be the lines or the master cylinder. Help here please. Thanks in advance.
                              84' 300ZX 2+2 NA (Hardtop)

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