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Brake Bleeding a '93 GMC pickem-up

This is a discussion on Brake Bleeding a '93 GMC pickem-up within the Technical / Maintenance forums, part of the General Discussion category; It's a 2wd 1/2 ton with 10" drums in the rear. Sun the pass. side rear wheel cylinder blew out ...

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    Brake Bleeding a '93 GMC pickem-up


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    It's a 2wd 1/2 ton with 10" drums in the rear. Sun the pass. side rear wheel cylinder blew out so last night I replaced the cylinder on the pass. side and drivers side. Bled the brakes and it looks like I got the air out and I have a good pedal but the "brake" light on the dash is still on... Is there a reset proceedure or could I still have air in the lines or could something else be wrong? Oh and at no time did I let the fuild in the master cylinder tank go dry.

    Also one question just so I can check my proceedure is there a write-up on bleeding brakes anywhere I the forum? I did a search and couldn't find it but that doesn't really mean much since I'm lowsy at searches.

    Thanks for the help.
    Last edited by SKFengineer; 08-07-2007 at 07:18 AM.

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    Re: Brake Bleeding a '93 GMC pickem-up

    I'm going to post a reply to my own question. I talked with my mechanic this morning and he was able to help me a little. I'm not sure about all OBS trucks but mine has the rear-abs thing only (I forget the name) and then the proportioning valve just below the master cylinder. If you remember in the post above I asked about the "brake" light still being on. Well I've learned that the light is set when there is a pressure difference between the front and rear brake; a piston/plunger in the proportioning valve offsets from center and triggers the light on the dash. Normally when that happens and you bleed and pressurize the bad line (front or rear) the proportioning valve resets. Since it is a '93 that makes my truck sort of an older truck and he said the valve can stick. The fix is to bleed my front brakes since the rear was where the problem was and if that does work tap on the valve lightly while bleeding.

    I'm still curious to see if anyone else has input but I thought I would share more
    Last edited by SKFengineer; 08-07-2007 at 10:13 AM.

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    Re: Brake Bleeding a '93 GMC pickem-up

    a
    Last edited by ToolOutfitters; 01-10-2008 at 07:21 PM.

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    Re: Brake Bleeding a '93 GMC pickem-up

    No the light went on after the cylinder took a dirt nap.

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    Re: Brake Bleeding a '93 GMC pickem-up

    Okay, in the interest of all those that search the forums for information I'll post a follow-up. Last night bled the whole system, front and rear, no air in the whole system. The pedal feels great and the brakes are working well, here's the catch... The "brake" light is still on, grr. Talked to my mechanic again and the same thing with the piston/plunger, he told me to un-plug the wire for a week and plug it back in a week later saying that a week's worth of driving should reset it.

    I was wondering if anyone else has run into this, I'll try the wire thing for a week and post back here next week.

    Hope everyone has a good day.

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    Re: Brake Bleeding a '93 GMC pickem-up

    a
    Last edited by ToolOutfitters; 01-10-2008 at 07:17 PM.

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    Re: Brake Bleeding a '93 GMC pickem-up

    Since the light goes out when I removed the single wire from the proportion valve I did not remove the wires from the RWAL computer. I just assumed that the proportion valve was the problem at that point... However we know what happens when one assumes. If the light goes out with the proportion valve wire un-plugged could the RWAL computer still be at fault?

    Thanks for the input

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    Re: Brake Bleeding a '93 GMC pickem-up

    your mech dosnt spend alota time with these trucks...theres a check ball in the proportion valve that must be reset when bleeding brakes or you will get the brake light warning till its reset
    heres a link for some info for ya
    http://www.autozone.com/az/cds/en_us...rInfoPages.htm
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    Re: Brake Bleeding a '93 GMC pickem-up

    That's funny I asked him about that check valve and he said he's never messed with it... I'll have to give him a hard time for that.

    So do I hold the check valve in the whole time I bleed the brakes, that's the way I understand it in the article you forwarded. Is it okay to leave it open the whole time as I go between wheels?

    Thanks for the information, this is very helpful.
    Last edited by SKFengineer; 08-09-2007 at 07:57 AM.

 

 

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