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S10 Brakes!!

Discussion in 'Chevy Trucks' started by Murray, Dec 17, 2001.

  1. Murray

    Murray Junior Member
    Messages: 21

    HELP!!
    I live in Scotland, I bought a 1987 Blazer S10, 2.8 manual with soggy brakes, thinking I could cure them easily - WRONG!! With a lot of help from Alan in Vt., I have changed the calipers, wheel cylinders, master cylinder, pads shoes and hardware, and STILL soggy brakes! I've bled and re-bled this thing, but no improvement. The only thing in there that's not brand new is the proportioning valve. Could that be the problem? The pedal sinks pretty far with the engine running, about 5-6" before any resistance is felt. My friend has the same fault on three S10's. Do these things all have bad brakes? Is it the valve? There's nowhere over here to take the car to, mostly I do the work myself, but this has got me beat.
     
  2. plowking35

    plowking35 2000 Club Member
    from SE CT
    Messages: 2,923

    the valve could have defaulted, but I would look into the booster as well.
    Dino
     
  3. Murray

    Murray Junior Member
    Messages: 21

    Thanks, but I looked into the booster, and it seems okay. The pedal is still not perfect without the engine running, but is better. Start her up and the pedal becomes much lighter, implying the booster is working. Also, pumping the pedal brings the revs up as the vacuum is depleted. Sheare Chevrolet say it sounds like the valve, but say I need to pressure bleed the system - PROBLEM! How do you get a seal on the master? I drilled the top from my spare master, and fitted it up with the tube from a pressure bleeder, but even with a half dozen cable ties holding the lid on, fluid and pressure escape everywhere!Back to the drawing board. Any suggestions?:(
     
  4. DaveK

    DaveK Senior Member
    Messages: 420

    Make sure the rear brakes are adjusted correctly. Whenever the pedal is low, that is the first thing to check. Spongy pedal is not the same as a low pedal.
     
  5. Murray

    Murray Junior Member
    Messages: 21

    Thanks, but new adjusters fitted, and set as snug as the drums will allow.
    Told you it was a hard one!!
     
  6. DaveK

    DaveK Senior Member
    Messages: 420

    I know you won't want to hear this but I have gotten bad master cylinders right out of the box.
    Once you are confident that all the air is out of the system, which could be quite a bit with new calipers, master and wheel cylinders, everything points to the master cylinder.

    The proportioning valve (really a combo valve) won't effect pedal travel. It warns you when you lose front or rear brakes through the brake warning light. It applies pressure to rear brakes slightly before the front. And it gives the rear brakes a lower percentage of breaking power than the front. None of which, if not working correctly, would give the symtoms you have now.
     
  7. Alan

    Alan PlowSite.com Addict
    Messages: 1,393

    What Murray is going through is very similar to the ordeal I've been having with my 88 S pickup. So far the dealer has replaced just about everything but the lines on this one and still no rear brakes. We had a serious discussion about the bill I got with no results and the attitude of the wisea$$ service manager. They settled for parts and labor at actual cost rather than find the problem as opposed to throwing parts at it.

    Front brakes work so-so at this point, rears are a joke. Shoes are adjusted very tight and are in new drums and on new backing plates. Stuffing the pedal to the floor and blipping the throttle will spin the rear wheels with no load on the drivetrain. With the rear jacked up and wheels turning at 30 or so, pound the brake pedal and you can watch the wheels slow down, not an alomst instant stop like there should be.

    I haven't found time to hook up the power bleeder yet, but that's getting close to the top of the project list. Hopefully that will produce results.
     
  8. thelawnguy

    thelawnguy PlowSite.com Addict
    Messages: 1,011

    I would replace the rubber lines (two in front and one at the axle). Cheap, but if they are soft they will expand rather than send pressure to the cylinders.
     
  9. Alan

    Alan PlowSite.com Addict
    Messages: 1,393

    Done that too!
     
  10. DaveK

    DaveK Senior Member
    Messages: 420

    Alan, didn't the dealer power bleed them?
     
  11. Alan

    Alan PlowSite.com Addict
    Messages: 1,393

    I'm not sure just how they did bleed them, I never asked. But, in light of some of the workmanship issues I tend to doubt they HAVE a power bleeder. They replaced both lines across the rear axle,, with stock lengths of tubing, then made a big "U" bend out of the excess and tucked that down UNDER the axle, on a 4x4, no less. What a wonderful place to snag them! Makes me wonder if they have a flaring tool and/or the ability to make a line to the right length.
     
  12. DaveK

    DaveK Senior Member
    Messages: 420

    Oh, that type of dealership. Just be glad they weren't putting an exaust pipe on. It's kinda hard to make loops with that. lol
     
  13. CT18fireman

    CT18fireman Banned
    Messages: 2,133

    Not sure if one exists on the s-10 but I had the problem with the load sensing valve on my Toyota. This is a valve on the rear end that when the bed settle from a load changes pressures sent to the rear brakes. After replacing the lines I had to bleed and reset mine so that I got rear brakes and a solid pedal.
     
  14. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    S10's do not have a load sensing valve,Alan,did you put a new proportining valve on?If not do it,if that isnt it,Id put a hydraulic pressure guage on the rear wheel port,I betyou master cyl isnt developing the pressure it should.How does the E-brakes work,will they lock up the rear wheels?,if not the shoes may be glazed over,Ive had brand new brakes hoes,that for wahtever reason,wouldnt stop the truck,im not sure if compound was wrong,or what.I put Geniune GM shoes on out of frustration,and problem solved,those Gm brakes shoes/pads are $$,but they seem to stop the truck better than the rest.If your master checks out strong,Id go with a manual,adjustable proporting valve,you can get them from Summit racing,mount it undrt the cab,you will be able to adjust the rear brakes for more bias,when you have lot of weight in the back.One other thing,do you have at least 500 miles on the brakes,since the new drums,and shoes were replaced,Ive found it takes that long sometimes to get them to work to their full potential,they need to be bedded in.
     
  15. Murray

    Murray Junior Member
    Messages: 21

    A couple of questions, guys. First, does anyone have a method of sealing the pressure bleeder onto the master? I'm going to try and make something up, with a couple of pieces of steel bar, one top, one below, a couple of screwed rods to clamp the whole thing, and I will try to make up a rubber plug with the pipe from the bleeder through it that will sit on the orifice in the bottom of the reservoir for the master. Next, can I bleed one side at a time, rears then fronts? If not, then my method is not going to work. And lastly, to prove the valve at fault, could I just put the lines straight to the master, at the risk of too much pressure at the rears? If so, I guess I could learn to drive with that!Thanks for the tips so far.
     
  16. Knightcrawler

    Knightcrawler Junior Member
    from ohio
    Messages: 28

    spongy s-10 brakes

    did you see if the vacume hose coming off your booster is cracked or split and isnt leaking from the tbi, whenever i lower an s-10 this becomes a problem and a new hose must be placed on then clamped tight or the exact thing you describe will hapeen
     
  17. Murray

    Murray Junior Member
    Messages: 21

    I'm pretty sure there's no vacuum leak, but not certain. I did have one when I changed the PCV, and although I didn't notice it on the brake pedal, the engine was revving to about 2500 rpm, and the 4-wheel to 2-wheel shifter was taking an age to react. I will have another look when it gets light out, though. Thanks.
     
  18. DaveK

    DaveK Senior Member
    Messages: 420

    A leak in the booster line will make the pedal a little firmer when applying the brakes. And you would probably be able to tell by simply stepping on the brakes. Kinda like using the brakes when the engine isn't running.

    I just thought of another posibility. There is an adjusment (not totally sure on the S10) for the gap (or lack of) between the rod that applies pressure and the piston in the master cylinder. If it is adjusted to far, it wouldn't let the piston return fully to the normal state. If the gap is to large, the pedal would move quite a distance before beginning to apply the brakes.

    This is just another theory, but hey, you are running out of options. :)

    And remember, I do know that on some vehicles it is adjustable, but I am not 100% sure on the S10, so don't go breaking anything trying to adjust something that can't be adjusted. :)

    Dave
     
    Last edited: Dec 23, 2001
  19. plowjockey

    plowjockey PlowSite.com Sponsor
    Messages: 622

    When I used to set the e-brakes on the S-10's on the line at GM we would depress the e-brake pedal to a pre-determined point and then pull out or back on the brake pedal to set the booster rod length. This was when the boosters had just been installed and the engine had not as of yet been started. I don't know if this would work on a vehicle that had been used or not.

    Bruce
     
  20. staley52

    staley52 Member
    from Iowa
    Messages: 98

    Ok former GM tech here

    first off it is not the booster if there was a booster problem the pedal would be hard not soft

    next for those of you using a preasure bleeder do not use more than 10 to 12 psi you will get a better and faster bleed, and not blow off your cap

    next can you pump the crap out of the brakes and get a good pedal feeling and brakes at all 4 if you can there is 2 options there is air in system or a bad proportioning valve this prosess will also eliminaate the hoses doing this will usually blow any soft hoses now if the pedal only improves slightly or not at all you have a bad master on one car I had to install 2 remans then 2 new units with the 2nd new one working to get brakes

    One thing that I hope is common knowlege is do not mix brake fluid use the recomended fluid i.e. dot 4 if you mix it has been known to eat seals espesialy dot 5 in a 3 or 4 system
    now you can up grade from dot 3 to 4 but not to 5 just be sure to flush out all the 3 and I repeat do not use dot 5 unless specificly called for in manual and s10's don't call for it