Master brake cylinder

Discussion in 'General Chevy & GM Tech Questions' started by ratbag, Nov 15, 2010.

  1. ratbag

    ratbag New Member

    After bench bleeding the brake master cylinder do you have to bleed your brakes at each individual wheel or not. I have never done the job before but it looks pretty straight forward. If anyone has any tips I would appreciate.

  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    Welcome to the club Ratbag. If you have an older truck then yes you should probably bleed them all, but if no air has gotten into the lines you may not have to bleed the wheel cyls. & if you have a newer truck this could be an issue.I don't know how old your truck is but there have been some problems with people trying to bleed their own brakes on newer vehicles. Some have to be taken to the dealer & bled with the GM Tech 2 bleeder unit to get ALL the air out, otherwise the pedal remains spongey..
  3. IT-Guy

    IT-Guy Member

    I have a 96 Z71 and just performed a full brake job on mine and yes you have to bleed the brakes at the wheels after a M.C. replacement. This is also a great time to inspect the hardware of your braking system to include drums (springs, pins, slave cylinders). What year is your vehicle.
  4. stephan

    stephan Rockstar 4 Years 5000 Posts

    Hey Ratbag, before you bleed your brakes you should read this page at this link below. I still don't know what year your vehicle is, but if it's a newer one with ABS, & you try bleeding them, you may cost yourself a hundred dollar bill at the dealership to have your brakes Re-bled with the GM Tech 2 bleeder. Since you bench bled the master, I would try them first without bleeding them as you will probably put more air into the system, that only the Tech 2 bleeder can remove.

    I'm not a 100% sure everything the T-2 bleeder does, I know it opens the bias valve all the way, as far as the ABS I'm not sure what it does to that while bleeding.
    My understanding is it overrides the speed sensors and opens the wheel cylinder valves to allow them to flow, I always thought you could do this by removing the ABS sensor but a GM tech told me doing it this way you miss a step that allows the lines to still hold air, the wheel cylinder valves dont open all the way when the sensors dont record any speed.
    Depending on the truck they started using it as far back as 96 on 1500's, around 97 it started showing up on 2500's.
    I've bled the brakes on my previous 98 without the t-2 tool (by pulling the ABS fuse) but I never got that solid feeling, the next owner took it to a GM garage and said they got quite a few bubbles out of the lines, so I know it does make a difference.

    other link didn't work, try this one Ratbag.
    Last edited: Nov 16, 2010
  5. vms4evr

    vms4evr Rockstar 100 Posts

    The TechII bleed when all else fails will get air out of the ABS. One thing you can try before paying GM to bleed your brakes is to cycle the ABS yourself the good old fashioned way. Take the truck out and stand on the brakes and engage ABS. You can find a gravel/dirt road where the ABS engages easily on hard braking. Do it several times. It moves the air down the lines. If you're lucky it gets them out of the ABS into the line where it will move out the bleed screw. Short of that you are stuck paying the dealer.

    When they do the TechII bleed the unit does cycle the ABS relays and gets each line cleared. I've heard of pulling fuses and some creative tricks to fake out the ABS into cycling the relays. I've yet to hear of a good solid result short of actually slamming the brakes to engage them as they would normally.
  6. stephan

    stephan Rockstar 4 Years 5000 Posts

    Great idea VMS.----> ""cycle the ABS yourself the good old fashioned way. Take the truck out and stand on the brakes and engage ABS. You can find a gravel/dirt road where the ABS engages easily on hard braking. Do it several times. It moves the air down the lines.""

    I never thought about trying that. I was wondering if you could support the veh. with jack stands on all 4 corners & run it about 30-40mph (with a driver in the seat of course) & bleed them that way. Do you think this would work if your idea didn't?
  7. vms4evr

    vms4evr Rockstar 100 Posts

    I wouldn't be too keen on that idea personally. I'd be at the point where I would just pay the dealer and get the Tech II bleed done. They'll completely purge and flush the system at that point. Sometimes it is worth it to avoid the aggravation and wasted time. You do your best in your garage. Then when all else fails you get stuck in situations like this.
  8. ratbag

    ratbag New Member

    Master cylinder

    Sorry, I forgot to post the year of my truck. Its a 2002 Silverado 4x4 4.8 liter. I appreciate the responses as I have never been much of a car guy but I have been doing some of the easier jobs that I can to save some $$. They wanted $300.00 for the master cylinder job. So what I took from this was, do the master cylinder job and test brakes, if no good bring to tech to have bled.
  9. stephan

    stephan Rockstar 4 Years 5000 Posts

    Yep, I hear ya ... all the new tech is great, until it costs some poor bastard $100. for a brake bleed ha ha ha... then it kinda SUCKS!!:grrrrrr:

    ---------- Post added at 12:17 PM ---------- Previous post was at 12:06 PM ----------

    I don't blame you one bit Ratbag. $300 for a master cyl. job is frickin ridiculous!!
    You're still going to come out ahead, even if you have to go to GM for the bleed, so it was definitely worth your time doing this one yourself:great:

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