Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Brake Master Cylinder

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by kd7kmp, Nov 19, 2004.

  1. kd7kmp

    kd7kmp Registered Member

    Joined:
    Jun 2, 2004
    Posts:
    99
    Likes Received:
    0
    Location:
    Springivlle, Utah
    The only thing that is not new in my '90 Burban's braking system are the hard lines (it's a V1500). My issue is that the brake pedal is sooooooooooooooo mushy and I can't get adequate braking performance. I have noticed that the master cylinder squirts a "geyser" of fluid upward upon application of the brake pedal. This is from the rearward portion of the resevior--it feed the front brakes. Before anyone asks, yes, the system is completely purged of air...there is no doubt there.

    My thought for fixing this problem is a different master cylinder. I have looked at several GM trucks of the same year and they all exhibit the same problem. I have a 1977 G30 van that doesn't exhibit this "geyser" phenomenon. The brake pedal is rock solid and braking is great. Any ideas on a different master cylinder? Thanks for the help.

    Kevin
     
  2. k20

    k20 3/4 ton status

    Joined:
    Sep 9, 2001
    Posts:
    5,068
    Likes Received:
    0
    Location:
    Mineral Springs, NC
    goin out on a limb, as i have never dealt with one, but maybe has something to do w/ the anti-lock brakes? Thats the only thing that I can think of.
     
  3. divorced

    divorced 3/4 ton status

    Joined:
    Jul 20, 2004
    Posts:
    5,115
    Likes Received:
    0
    Location:
    .
    I put a new (rebuilt) master cylinder on my K20 and it still shot fluid out of it; I had to leave the cap on it while bleeding to avoid a big mess.
     
  4. kd7kmp

    kd7kmp Registered Member

    Joined:
    Jun 2, 2004
    Posts:
    99
    Likes Received:
    0
    Location:
    Springivlle, Utah
    K20,

    I thought of that. I actually bent up some hard line and bypassed the ABS. Braking was the same. Thanks for the thought.

    Kevin
     
  5. kd7kmp

    kd7kmp Registered Member

    Joined:
    Jun 2, 2004
    Posts:
    99
    Likes Received:
    0
    Location:
    Springivlle, Utah
    Divorced,

    This is the exact problem I am talking about. I think it is a poor design to bleed off pressure that would otherwise be put to use in stopping the truck.

    Kevin
     
  6. ZZ4x4

    ZZ4x4 1/2 ton status

    Joined:
    Oct 17, 2001
    Posts:
    542
    Likes Received:
    0
    Location:
    Garland, TX
    Not sure if there is a difference between hydroboost MCs and the regular kind, but most MCs I've bled eject fluid when you hit the pedal. In fact the instructions for bleeding brakes that I have says to watch for it as a sign things are working correctly. Hope it helps.
     
  7. kd7kmp

    kd7kmp Registered Member

    Joined:
    Jun 2, 2004
    Posts:
    99
    Likes Received:
    0
    Location:
    Springivlle, Utah
    ZZ4x4,

    Thanks for letting me know. This is the first time I've heard this. I will look into it.

    Kevin
     
  8. clarkjw24

    clarkjw24 1/2 ton status GMOTM Winner

    Joined:
    Dec 4, 2003
    Posts:
    3,531
    Likes Received:
    2
    Location:
    McBee, SC 29101
    Did you bench bleed it before installing. There is a difference in hydro and vac master cylinders but not in fuctionallity.
     
  9. kd7kmp

    kd7kmp Registered Member

    Joined:
    Jun 2, 2004
    Posts:
    99
    Likes Received:
    0
    Location:
    Springivlle, Utah
    I did bench bleed it. Thanks for the info.

    Kevin
     
  10. crawford

    crawford 1/2 ton status

    Joined:
    Feb 13, 2004
    Posts:
    229
    Likes Received:
    0
    Location:
    Vancouver, WA
    A lot of times the geyser means that air is still in the lines. It gets compressed when you step on the brake pedal. As soon as you let off the pedal the air in the line expands again shooting fluid back up the lines and making a geyser.
     
  11. socalblazer

    socalblazer 1/2 ton status

    Joined:
    Mar 18, 2004
    Posts:
    110
    Likes Received:
    0
    Location:
    Redondo Beach, CA
    The geyser is normal for many types of MC's. How did you bleed the system? I've experienced problems with manually (Pedal pumping) bleeding some systems, mainly hydro-boost. I've had to vacuum bleed these system to get a solid pedal and even at that it's not great, but it's better then the dreaded smooshy pedal. When you figure it out post up so we know. Good luck.
     
  12. imiceman44

    imiceman44 1 ton status

    Joined:
    Aug 5, 2002
    Posts:
    15,160
    Likes Received:
    1
    Location:
    Sacramento, CA
    The geyzer you see is normal on the newer style plastic reservoir MC.
    The earlier style cast iron tanks, you should always keep the cap on, it's the only thing pressurizing between the front and rear tanks if you don't have the cap on when you pump it the fluid will go the path of least resistance from the rear to the front reservoir. Bad design but that's how it works.
    :(
     

Share This Page