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WTF is up with my brakes?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sub_Versive, Sep 4, 2001.

  1. Sub_Versive

    Sub_Versive Registered Member

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    Anybody else have problems getting the TSM 14BFF rear disk brake conversion to work right? I installed the kit on my '85 suburban 4x4 and couldn't get them to bleed correctly (or so I thought). I wasn't happy with mangling the rear lines to match up to the flex lines, and I also didn't think they were bled properly - my pedal travels too far, and a second pump gives me lots better braking - so I re-routed the rear lines this weekend. The rear lines now go along the tops of the axle tubes, and I welded on the tabs to mount the tube ends and added a tubing clamp on the top of the tube. Then I tried to re-bleed the system. We never got a very good pedal, so I removed the master cylinder to bleed it separately. I couldn't get it to work well, so I took it apart and found some pitting. I replaced the M/C with a reman unit, and when I bench bled it, the difference was very obvious. The new unit had much more resistance than the old one. Installed it and tried yet again to bleed the brakes. We got it so that the pedal felt great - like 200% better than it has since I've owned the truck, but as soon as I started it, the pedal hits the floor when I try it. I also hear a "whoosh" sound coming from under the dash when I hit the brakes real hard. The brake warning light comes on if I hit them real hard, but a second pump makes it go away. I have to pump 3 or 4 times to get a solid pedal when driving. I adjusted the rear caliper parking brakes as best I could, but I'm not confident about them - there's still a bit much of a gap for my tastes between the pads and rotors. Any tips on how to adjust these? Additional info, I have also added Superlift braided lines to accomodate a planned 6" lift, and I have the braided flex lines at the rear calipers from TSM. I also replaced the front calipers and pads at the same time. AFAIK, I should have to call for help to press the brakes with the braided lines and a mostly new system, but that's not the case.... It looks great, just doesn't work. I realize this is a huge post, I hope that somebody here has seen something similar and can help me find what I've missed. Thanks,

    Jake Kooser
     
  2. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Are your bleeders pointed up or down? If they are pointed down, they make it hard to bleed properly.

    See my rig at <a target="_blank" href=http://coloradok5.com/gallery/Leadfoot>http://coloradok5.com/gallery/Leadfoot</a>
     
  3. Sub_Versive

    Sub_Versive Registered Member

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    The bleeders are DOWN when installed, but I got the flex lines (at the caliper) so I could move them to the other side of the rotor - with bleeders UP - to bleed them. When I bled them, the bleeders were straight up, pointing rearward. The only doubt I would have is if that is over far enough, but I can't move them any further without disconnecting lines...

    Jake
     
  4. rocko

    rocko 1/2 ton status

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    Sound's like the problem I'm having after my 14 bolt conversion.. But my friend Thomas.. noticed I had a bad wheel cylinder on the right rear.. brake fluid dripping out of the bottom of the drum..
    Going to check that.. and see if that fixes my problem.

    I haven't failed, I've found 10,000 ways that don't work. www.rocko.rockcrawler.com
     
  5. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    I hate to say it, but it sounds like the reman'd M/C is shot. I had the same problem years back (twice![​IMG]). I tried saving money by getting a rebuilt unit rather than new because of cost issues. I replaced the M/C with a rebuilt one, worked for a week and soft pedal again. After pulling out my hair trying to figure out what was wrong, I finally decided to replace the M/C again with a reman unit. That one lasted a month. I then got smart and bought a new one, and have had it on for 2.5+ years. It may not be the problem, but it sure sounds like it, especially since you bled the brakes correctly (bleeders up).
    My new phylosophy is to buy new High quality parts when it comes to replacing anything related to brakes or steering. I feel much safer knowing I did it right the first time (and actually costs less in the long run). Plus if you loose brakes or steering, you are pretty much screwed.

    See my rig at <a target="_blank" href=http://coloradok5.com/gallery/Leadfoot>http://coloradok5.com/gallery/Leadfoot</a>
     
  6. LittlePig

    LittlePig 1/2 ton status

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    Couple of things, maybe. First, your master cylinder may not have enough fluid capacity to move rear disks. Drum cylinders are much smaller, so the master clinder has a lower volume. Also, some GM vehicles had a valve on the proportioning valve that had to be depressed to get a good flow to the rear brakes, but I don't know if Blazers were on that list. Check that, it will look like a rubber-covered nipple sticking out somewhere on the valve (not the bleed fitting for the valve). You might also consider getting the thing power-bled, so you can be absolutely sure there is no air in the lines. It's not expensive (about $50) and any Midas should be able to do it. Also, you say that when you started it, you lost the good pedal feel. You may have lost your vacuum booster too. That happened to me during a brake job once. I had good vacuum before the swap, but all the pumping I did seemed to have killed the booster when I installed the new MC. There is a way to test whether you have, but I don't remember what it is. Hope this helps.

    Email: littlepig@keepandbeararms.com
    ICQ: 84108805
     

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