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  1. #1

    Default 1990 K2500 Suburban Brake problem


    Recently I replaced one front Brake Caliper as the old one was dragging.

    Then the next day the Brake warning light was on and the Brake Pedal felt softer than usual.After rebleading the Caliper the light still illuminated,however the soft Brake Pedal problem became intermitant.Although the Brakes are soft for about half of the Brake Pedals distance,the last half of its travel the brakes have full effect.

    I have checked all the connections on the Brake lines and all the Calipers and pistons for leaks.

    Any help is appreciated.


    Mike Hill

  2. #2
    Sr. Engineer
    Join Date
    Oct 2010
    Indianapolis, In


    Brake light will be on if the parking brake is engaged, be sure e-brake pedal is up all the way.There is a safety switch that may need to be reset that is on the brake bias or proportioning valve under a rubber cap. I have found poorly adjusted rear drums will cause a soft pedal travel until they engage. The farther out they are the longer the pedal travel is until it gets firm.
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

  3. #3


    Thank you for your reply,I will get in and have a look at them tomorrow.It just seems strange that this fault is intermitant.One minute the Brake Pedal feels fine (no travel before engaging) then a soft pedal and the warning light on.


  4. #4
    Sr. Engineer
    Join Date
    Oct 2010
    Indianapolis, In


    The light is intermitant as well or the soft pedal and light occur at the same time? An easy way to check for rear brake adjustment issues is to utilize the parking brake. Try this.... You will be using the parking brake to bring the lining up close to the drum. Engage the P brake while holding the release handle, when you feel the brake start to get firm, stop, then release about 1/2 inch and let the handle go to lock the pedal in that spot. I can't say if the brake won't be dragging a bit but it won't be much if any and no harm if just driving around the block a time or two. Now see if your brake doesn't feel alot better. If not, then the brakes were not far out of adjustment to begin with and I am out of suggestions. If it got better then adjust your brakes.

  5. #5


    did you bleed the brakes after you changed your caliper.your old caliper most likely was not the problem the rubber brake hoses colapse on the inside and want let the pressure off causeing the caliper to drag. i suggest to change the brake hose to.ive done been down that road.

  6. #6


    dpeter and KW70Chevy.Thankyou for your replies,I am changing the other Caliper tomorrow and will order new flexable front Brake Hoses.I will try the trick of applying the Ebrake and driving it.

    Will let you know how I got on.

  7. #7


    Quote Originally Posted by dpeter View Post
    Hey Mike Hill, That parking brake exorcise will only work with drum brakes and not rear disk. Didn't mean to be unclear about that. Good luck and I would second the move to change brake hoses. I also have had instances where colapsed hoses have confounded my best efforts. The counter guys at the parts store must have been saints to keep taking back and exchanging "bad" calipers from me until someone clued me in about flexable lines.

    The saga continues..... I have blead the system three times,adjusted the rear brakes,replaced the power steering pump ( I saw it runs to the servo,so I thought since I had a spare one I would try),replaced both Calipers and pads.

    I have not replaced the front Brake Hoses as they have not arrived from the USA yet.

    The problem feels like "air in the system" you can pump the pedal untill it gets hard,then after releasing the pedal the next stroke could be soft again.The Brake warning light goes off when the Brake it pumped up hard.

    One minute the Brakes are "spongy" the next minute rock hard.

    I have watched the fluid level in the resovior when the Brake pedal was being pumped,it rises and falls like it should.I hope it is not the master cylinder at fault?

    Perhaps I should,try bleeding the Brakes yet again,it does make the problem go away...untill the next morning.I have not seen any bubbles in the fluid being pushed out the the nipples at either the Calipers or the rear brake Cylinders.

    Thanks in advance for your help.

    - - - Updated - - -

    Quote Originally Posted by dpeter View Post
    Brake light will be on if the parking brake is engaged, be sure e-brake pedal is up all the way.There is a safety switch that may need to be reset that is on the brake bias or proportioning valve under a rubber cap.
    I had a look for a Brake bias valve,but could not find one.The ones I have seen are mounted on top of the rear axel housing,there is no such valve on my Suburban.

  8. #8
    Sr. Engineer
    Join Date
    Dec 2011
    11-22-boogie woogie avenue


    When you replaced the calipers are the bleeders on top?
    Both sides will fit each other but have seen people install where bleeder would be upside down..air rises never will get bleed right. Just a thought.

  9. #9


    Yes,the bleeders are on the top of both Calipers.

    I was wondering if the problem might be the Brake Servo?I have no knowledge of them really,it might explain the intermittant fault as well as the vauge and then massive braking power?

  10. #10


    After bleeding the system yet again...

    I searched on the internet for other possible causes of the spongy brake.The proportioning valve seems to be working,when you push the pedal in,a small brass coloured pin protrudes from the valve.

    None the less I tried these other "fixes"incase the proportioning valve needed to be reset.

    Driving backwards and jambing on the Brake.This produced regular braking after a few attempts,so we bled the system again.
    Striking the Brake pedal with a large hammer.

    So I think the next step is to change the master cylinder and proportioning valve.

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