Serious Brake Failure

Discussion in 'Lifted & Offroad Suspension' started by cdvntx, Jun 14, 2009.

  1. cdvntx

    cdvntx Rockstar

    Here I am needing help again. I have a '99 K2500 'Burb w/ 7.4L motor. The brakes are hydraulic boost assisted. I lost my brakes and power steering exiting the freeway the other day. After I got it back under control and slowed, everything came back. I then noticed, with enough pedal pressure, I could put the pedal to the floor; engine running or not. I thought no problem and bought a new master cylinder. No change. Somebody hep me please!
  2. ct9a

    ct9a Epic Member 5+ Years 1000 Posts

    Glad you didn't wreck when you lost your brakes. The only thing that I can think of is a vacuum leak. I'm not even sure that the P/S system uses vacuum since it's run by belt. The pedal going to the floor thing is common among Suburbans. For some reason they have a really crappy pedal feel to them, mine goes to the floor without much effort at all.
  3. cdvntx

    cdvntx Rockstar

    Yeow! That's scary and can't possibly be right. If it is. it kind of makes it useless for a tow vehicle.
  4. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    I've seen quite a bit of discussion about pedal feel on OBS GM trucks. It seems that some people have a hard time getting a good firm pedal feel.

    Vacuum issues usually don't cause you to lose braking completely. The brakes are harder to press. Pedal going to the floor is usually some kind of hydraulic issue. Have you inspected the brake system for leaks? I've heard of rubber hoses deteriorating to the point that they "balloon" when you apply pressure, which will cause excessive brake travel. Are the rear brakes working and adjusted? A big part of pedal "feel" is how well the rear brakes are adjusted.

    It sounds like it's time for a fairly thorough inspection of the brakes.

    I'm not sure what the connection would be between brakes and power steering.
  5. mmad16

    mmad16 New Member

    on my o7 tahoe the tire pressure monitor system threw off my ABS and now im always losing brake pressure.
  6. cdvntx

    cdvntx Rockstar

    The level remains constant in the reservoir and there is nothing obvious. I'll look at the rubber portion of the brake lines for expansion and check that, but that doesn't seem likely, as that would be consistent.
    The only connection between the brakes and power steering is the hydraulic assist to each. The new master cylinder seemed to help some, so I think I'll try bleeding the brakes the old fashioned way: pump, hold and bleed....
  7. 2COR517

    2COR517 Epic Member 5+ Years 1000 Posts

    With HydroBoost, you can rule out vacuum issues. You said you lost power brakes and power steering at the same time. The common link is the pump and the plumbing. Look there. Maybe you had a piece of debris block the return line, cutting the pump off. Or a line with internal damage. It probably wouldn't take that long to pull the pump and lines. Flush everything out and put it back together. Of course, the pump may be simply bad. As for bleeding the brakes, I believe you need a scanner to actuate all the ABS Solenoids to get the air out. Maybe that's just the newer ones.

    It's also possible the belt slipped. Is it old?
  8. grimreapersshadow

    grimreapersshadow Rockstar 100 Posts

    chances are your powersteering pump is going out or your hydra boost system is dead fairly simple setup check your lines and such like 2cor sayed and take your serp belt off and see if your powersteering pump pulley wiggles or comes off with the nose of the pump attached like ive seen in many avalanches that have hydra boost setup
  9. cdvntx

    cdvntx Rockstar

    Great advice guys. I'll check out those issues and see if it does the trick.

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