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 Guru's, Need some Help!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MudFrog, Nov 3, 2002.

  1. MudFrog

    MudFrog 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    3,236
    Likes Received:
    0
    Location:
    Daleville, Va
    Brake Guru\'s, Need some Help!!

    My brakes have had issues ever since I did the 3/4 ton swap last year. It seems as if my Master Cylinder is always going bad, well thats according to the brake shop. No matter how hard I try I can not get a pedal back and always have to take it to a shop to get power bled. In fact my master cylinder went out on me 3 weeks ago and after I was unsuccesful in bleeding the brakes I had to take it to the shop, they powerbled it and got me some pedal but in no way was the braking what it should have been. Well 2 weeks ago my rear passenger drum just completely locked on me, so instead of fooling with the drums I went ahead and purchased the parts to do a rear disc brake conversion. Well I finally had a chance to switch it over last night, everything went great except for the fact that I have no pedal again. I bled and bled and bled the system. I cannot find any air in the lines or master cylinder. If you push the pedal down it's just a nice smooth stream of brake fluid that will spout out from any of the bleeding points. And to top it all off I cant get the brakes in the rear to work... I can mash the brake pedal to the floor and the rear tires will still spin by hand, but at the same time they are currently getting plenty of brake fluid to them, I can open the bleeder nipple and press the pedal and a stream will flow out. I'm at a loss, it seems as though something is really wrong.

    I forgot to mention that in the past I have had trouble with not getting any fluid to the rear brakes. I could open the bleeder nipple and push on the pedal but nothing would come out. Obviously I can understand why this would have happened last night but when I bled them 3 weeks ago it was happening too, which doesn't make sense because it had been driven for about 6 months with out anyone even touching the brake system.

    So should I try a New master cylinder instead of a rebuilt one? I know the rebuilt ones are junk anyway but I would have thought they would last longer then 3 weeks. Do you think the booster or proportioning valve could be causing the fluid to barely reach the rear and give me no pressure?
     
  2. sosamantx

    sosamantx 1/2 ton status

    Joined:
    Aug 14, 2000
    Posts:
    393
    Likes Received:
    0
    Location:
    somewhere in Texas
    Re: Brake Guru\'s, Need some Help!!

    lol, i don't have the answers (i have the same problem on my nova), however maybe this will help? i've copied it from elsewhere. also, you'll need to change your proportioning valve (or get an adjustable one for the rear, since you changed it to disk brakes!!). the last part paragraph (i've actually read in my hot rod magazines), but this is why i say you need to get an adjustable valve.


    How and why do I bench bleed a master cylinder?
    When installing or replacing a master cylinder, it is critical that all air is removed from the master cylinder. This can easily be done by bench bleeding the master cylinder prior to installation. Using the SSBC master cylinder bleeder kit (#0460):

    1) Place your master cylinder in a vise by the ears (not body). Make sure it is level.
    2) Attach a piece of clear plastic hose to the short end of one of the plastic
    nozzles. Do the same to the other hose and nozzle.
    3) Clip the plastic bridge to the wall and push the ends of the hose through the holes so they are SUBMERGED in the reservoir on either side of the wall.
    4) Press the tapered end of the nozzle FIRMLY into the cylinder port hole with a twisting motion. Repeat this procedure on the other port hole.
    5) Fill the reservoir with CLEAN brake fluid recommended by the manufacturer.
    6) Using full strokes, push the piston in, then release. Do this until ALL the air bubbles have disappeared from the clear plastic hose.
    (CAUTION-MASTER CYLINDER WILL NOT BLEED PROPERLY UNLESS HOSES ARE SUBMERGED IN BRAKE FLUID UNTIL THE BLEEDING PROCESS IS COMPLETED.)

    Now mount master cylinder and avoid brake fluid leaking out of front and rear ports during installation.



    When installing brake calipers, lines and hoses, how do I bleed the system? When installing brake calipers, lines and hoses, how do I bleed the system?

    Always bench bleed master cylinder first, then the system. There are four methods: gravity, pressure, vacuum, and pedal bleeding. The most common is pedal. This process is as follows:

    1) Pedal bleeding is a 2 person job - one person pumps the pedal, and the other operates the valves. Open each bleeder valve individually, then depress the pedal one full stroke. The person watching the valves looks for air bubbles and closes the bleeder valve before the pedal is slowly returned to the released position. (NOTE: To assure that no air is siphoned into the system, a plastic hose should be connected to the valve. The other end of the hose should be submerged in container of brake fluid. Also, the valve must be closed at the end of each stroke before releasing the pedal.)
    2) Continue in this manner until all calipers are bled.
    3) After each caliper is bled, refill the master cylinder and frequently check the reservoir.
    4) Bleed the longest line first, following this order: right-rear-outer, right-rear-inner, left-rear-outer, left-rear-inner, right-front and left-front.



    What amount of pressures are needed to stop my car?
    Optimal brake pressure varies by vehicle and the type of brakes being used. Disc brakes generally require 1,200 - 1,400 PSI for proper operation, while drum brakes require only 600 - 800 PSI. Other factors which affect pressure include weight distribution, tire/wheel size, and suspension type. For example, a car that is very nose heavy and has narrow rear tires with rear disc brakes may only be able to tolerate 800 PSI before brake lockup occurs. A car that is well balanced and has a wide rear tire with rear disc brakes may tolerate as much as 1,200 PSI before lockup. For this reason, Stainless Steel Brakes recommends an Adjustable Proportioning Valve (right), which allows fine adjustment to optimize the brakes on specific vehicles. The idea is to prevent rear wheel lockup during severe braking. <font color="red"> </font color>
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Re: Brake Guru\'s, Need some Help!!

    Bypass the Proportioning valve. It's biased wrong for Disc rears.
    Check all your rubber lines. Have somebody stand on the peddle and make sure that you don't have any that are balloning.
    Most people say that the 1/2 ton Master will do the job when running 1 ton gear or rear disc's but there are a few that have replaced the master with a 1 ton unit.
     
  4. 95 Silverado

    95 Silverado 1/2 ton status

    Joined:
    Nov 9, 2001
    Posts:
    467
    Likes Received:
    0
    Location:
    Central PA
    Re: Brake Guru\'s, Need some Help!!

    What master cylinder and prop. valve are you using. Both are sized for the system they are being used with, since your system has been completely modified your stock parts may not provide the best performance. I would get a correctly sized master cylinder for a 4 Wheel disc set-up, run the front two brakes direct from the master cylinder and use a variable proportion valve on the rear brakes so you can adjust the amount of rear brake to your needs. It sounds like the proportioning valve is your problem now.
     
  5. sosamantx

    sosamantx 1/2 ton status

    Joined:
    Aug 14, 2000
    Posts:
    393
    Likes Received:
    0
    Location:
    somewhere in Texas
    Re: Brake Guru\'s, Need some Help!!

    sorry for the long posts, just thought it might help??!! /forums/images/graemlins/wink.gif

    http://store.summitracing.com/partdetail.asp?part=679 &lt;-- valve
    http://store.summitracing.com/partdetail.asp?part=8990 &lt;--valve
    http://store.summitracing.com/partdetail.asp?part=16757

    some more stuff i found.





    Subject: 14 bolt disc brake conversions
    posted: 2002-10-20 19:52:02.0
    80chevrider
    when you do a disk brake swap on your 14 bolt
    do you need a different master cylinder with more fluid capacity for the rear circuit to compensate for the more fluid comsumption of disk brakes?
    Author Subject: 14 bolt disc brake conversions
    posted: 2002-10-21 05:17:50.0
    rxt60
    Not really, Most trucks with disc and drum brakes compensate for the difference with a proportioning valve, located in your brake lines somewhere below the master cylinder on the frame rail. The PV regulates the differences by limiting the amount of fluid to the rear drum brakes. Some cars with 4 whell discs do not use a PV at all while some have different PVs. You can get an adjustable PV from Wildwood brakes.

    A proportioning valve is a pressure reduction device. It is typically installed in the rear brake line to reduce braking efficiency and compensate for premature wheel lockup; a result of incorrect front to rear brake bias. An adjustable proportioning valve permits incremental adjustments to fine tune brake bias.

    A: A crossover tube is the external tube on a caliper that transfers fluid from one side of the caliper to the other. Some calipers have internal fluid passages and do not require crossover tubes.

    Q: What do I do to eliminate a spongy pedal?
    A: A spongy pedal can occur for a number of reasons: air in the line, misaligned caliper, incorrect caliper/master cylinder bore combination and more. See our complete Troubleshooting Guide for a more thorough list of causes and solutions.

    Q: Why does my pedal "fade" or "go away" after I've warmed up my brakes?
    A: Old brake fluid is the main cause of this problem. Brake fluid deterioration occurs from heat cycling and absorption of moisture. As brake temperatures increase, the old fluid boils, causing the pedal to fade. See our "lose your pedal" section of the Troubleshooting Guide, and make sure you are using fresh Wilwood brake fluid.

    Q: I have a hard pedal, but the car won't stop. Why?
    A: Common contributors to "hard pedal, won't stop" issues are oversized master cylinder bore and inadequate pedal lever ratio. See our Troubleshooting Guide for more complete information, and make sure you have Wilwood Quick Check Pressure Gauges available to assist you in evaluating the problem.

    http://www.wilwood.com/products/troubleshoot.html
    http://www.wilwood.com/products/techtiplocator.asp
     
  6. MudFrog

    MudFrog 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    3,236
    Likes Received:
    0
    Location:
    Daleville, Va
    Re: Brake Guru\'s, Need some Help!!

    This morning I went and gravity bled the system. The blazer is stoppable now but it's still not as good as it should be. I priced a new 1 ton master cylinder and I think a rebuilt booster from Autozone for $150 total, plus they will let me trade in my current master cylinder and booster. The 1 ton stuff is made by Fenco.. are these any good?

    They don't cary proportioning valves, but I can probably get a wagner proportioning valve and maybe even the master cylinder and booster from Wagner through my dads company, it will just be more $$ then the Fenco.

    I think I'm gonna try and bleed the Master Cylinder one more time but it is a rebuilt unit and I don't think it's worth the time to fool with it. I haven't had any luck with the rebuilt ones... yet I keep getting them?? Hmm... /forums/images/graemlins/wink.gif

    I'm deffinitely wondering about the proportioning valve... however I thought there were a ton of people on here who did D60 and 14 bolt w/disc swaps and didn't have to touch any of their brake system. Maybe I'm the oddball.... again.
     
  7. JIM88K5

    JIM88K5 1/2 ton status

    Joined:
    Apr 27, 2001
    Posts:
    1,384
    Likes Received:
    0
    Location:
    Vancouver, Wa
    Re: Brake Guru\'s, Need some Help!!

    I'd be looking at the prop. valve or look for a pinched hard line somewhere. if you keep replacing the same parts and it stays the same, you are replacing the wrong parts.
    How is the rear brake hose ? I'd take it to a shop and have it presure bled.
    Jim
     
  8. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Re: Brake Guru\'s, Need some Help!!

    What calipers are you running in the back? If they're the Caddy calipers with parking brakes, you won't EVER get a firm pedal, until you take the slack out of the calipers. You have to remove the nut that holds the lever in place and then rotate the lever forward (as if the parking brake is being applied). When you get to the forward end of travel, remove the lever and reindex it to the parking brake shaft so that you can rotate it forward again. When you can't rotate it forward any more, then the pads are in position close to the rotor. Reinstall the lever in its rearward position. Now you should have a firm pedal. /forums/images/graemlins/cool.gif
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Re: Brake Guru\'s, Need some Help!!

    Ok you saved me a post /forums/images/graemlins/smile.gif Now how do you back it off to install new pads when that time comes? How about a picture of how you got the parkijng brake to work with the K5 cables?
     

Share This Page