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Can't stiffen up the brakes. What to try next?

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by EzraBrooks, Sep 7, 2013.

  1. EzraBrooks

    EzraBrooks New Member

    I bought my 99 C2500 Suburban LT almost two years ago. I had the brakes checked out then and was told the pads and shoes were thin but ok. The rest was mechanically sound. But they felt softer than I would expect them to, and the truck pulls a bit to the right when braking. From what I've read, the pulling is pretty normal with rear drums.? Since then, much has happened to them.

    Replaced the front pads with high quality.
    No change.
    Had a front caliper seize up, due to a bad line that I probably aggravated while changing the pads. Took the opportunity to replace the both front calipers, brake lines (flexible, not steel), rotors, and bearings, and bled the front lines.
    No change.
    So I replaced the rear shoes and hardware, but not the cylinders.
    No change.
    Then they got worse. Really soft. Like scary to drive soft.
    Did some homework and testing and determined the master cylinder was bad.
    Replaced the master cylinder (bench bled the new one), bled all four lines (in this order: passenger rear, driver rear, passenger front, driver front).
    Back to start. Still softer than I'd like. Other people that drive it, say whoa, those brakes are soft. They are noticeably softer than my brother-in-law's 3/4 ton pickup.

    What next? I really don't want to tackle the brake booster because I likely don't have the right tools. I'll replace the rear cylinders if I have to, but my gut tells me that wouldn't cause this, but I don't know for sure. I'm worried about breaking something taking off the old ones. They look pretty old and there is very little room to work between the drum and the leaf springs.

    My other thought is to take it in somewhere, but I get the impression that most shops will want to re-do what I've already done, at least partially, (like change pads and shoes) and charge me for it.

    What do folks think should be next?

    Rear cylinders?
    Booster?
    Shop?
    Something else?

    Any other tests I can do to pinpoint the source of the issue?

    Thanks for your help.
  2. Pikey

    Pikey Active Member Staff Member 2 Years ROTM Winner 1000 Posts

    I only had an issue with drum brakes pulling if they were not adjusted properly. My 95 does not pull, my 90 safari van never pulled. That generation truck is know for soft brakes. On my 95 I switched all of the rubber lines (hoses) to braided stainless steel. Both fronts and the back one that goes from the frame to the junction block on the axle. It did stiffen my pedal a significant amount. Was it great? No! But, it was better. The pedal in it was so soft that I would push the pedal once quickly then let off and reapply the brakes to stop. I had also done pads, rotors, shoes, drums, and a master cylinder. As far as special tools needed to do the booster goes, I don't think that you need anything special. Just unbolt the master (many times you can leave the lines connected) unbolt the booster (it can get pretty tight under the dash) and remove the push rod from the brake pedal.

    Another thing that you could try is unplugging the abs pump under the hood. That should revert the system back to a regular hydro system minus the abs. I would try it and see if it makes a difference. My dad's 02 avalanche had a really soft pedal, it went all the way to the floor. We unplugged the ABS unit and it is fine. We just need to fix the ABS before the first major snow fall. Which in Michigan can be tomorrow.
  3. KidHauler

    KidHauler Epic Member 5+ Years 500 Posts

    You saw that cloud, too?

    My 99 brakes are also soft. I've only replaced parts as they failed, and mostly complained about the pedal feel. I think I read somewhere that it was a proportioning valve issue, but I've also heard that it's the hydro-boost, the abs, the ...
    I did recently manually adjust my rear drums, and they were out quite a ways. There may be something with the self-adjusters that keeps them from working properly. The brakes do feel better after the adjustment.

    I wish I had an answer better than - "hey, it's a 99 - they all do that"

    Good luck,
  4. Pikey

    Pikey Active Member Staff Member 2 Years ROTM Winner 1000 Posts

    The way to test the hydro boost (if equipped) Is to shut the truck off and depress the pedal 5 times to release the pressure built in the system. Then while holding you foot on the pedal, start the truck. If the hydro boost is working properly it should push the pedal back against your foot.
  5. EzraBrooks

    EzraBrooks New Member

    Well, the ABS wasn't the solution, but it gave me the clue I needed!

    After disconnecting the ABS and attempting to stop quickly, the front wheels locked up. But not the rear. No way in a truck this size should the front lock up before the rear on a road surface. So that told me the back brakes were useless.

    Upon attempting to adjust the rear brakes (through the whole in the back, with a screwdriver) I determined that I could not adjust them. So I took the drums back off and low and behold, I did something completely stupid when I replaced the shoes and hardware. I put the adjusters on the wrong wheels.

    So each wheel adjusted themselves to the point that the brand new shoes were barely touching the drums, even with the pedal pressed to the floor.

    Dismantled, switched the adjusters, all is right as rain. They still aren't crisp like a new car, but they work really well.

    Thank you all for your help once again. You guys rock!

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