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Thread: GM ABS scan/cycling tool needed!

  1. #1
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    GM ABS scan/cycling tool needed!

    Long story short, the Olds sent me sailing through an intersection a few weeks ago with no brakes when a line blew. Fast forward to today (last night really), she's in my driveway with all new hand-bent brake lines and two new wheel cylinders. I bled the system the usual way and have a firm petal with the ignition off but it goes to the floor with the engine running, so I figure I need to cycle the ABS valves to properly bleed this *grumbling*....thing. Does anyone have access to such equipment to bleed a late '90s GM ABS system?
    '98 Grand Cherokee 5.9 Limited, bone stock for now.
    '93 Grand Voyager wheelchair van, chick magnet.
    '90 Trans Am GTA, 5.0L/700R4, creaks and groans like a GM sportscar.
    '98 Oldsmobile LSS, 3.8L. The closest thing to decent mileage.

  2. #2
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    Okay I know I should bite the bullet and replace both calipers... I'm just not sure if that'll cure my problem.

    I just spent some time re-bleeding my brakes and manually tightening up the drums in the back. I had a couple of little bubbles in the back this time around. Again, engine off the pedal is firm enough I think. Engine running the pedal is way softer, over 4" of travel where it should be a little over 2". So I bled each wheel again with the engine running with no noticable change. Ever have a car that just fights you every chance it gets? *sigh*

    Which leads me to this part... I snapped a bleed screw on one of my calipers. One of my wheel cylinders too but I went ahead and replaced them both. One was factory with those stupid frigging little inverted torx bolts that not even my bolt-out extractors would budge. I *barely* got my Dremel in there to grind the heads off... But that's more of a bitter vent on my part than my problem. Anyway, the caliper. Since I snapped the bleed screw I figured I'd just bleed it by loosening the banjo bolt. The caliper should still be full of brake fluid since the banjo bolt hasn't been touched without pressure in the system. Still, it's a potential problem.

    I guess I'm just hoping that someone will confirm that I don't really need to replace those calipers too... lol And that someone has a miracle cure for my soft pedal. I might have to suck it up and take it to a shop to properly bleed the ABS pump but c'mon, that's a last resort.

    This is how I know the Olds is a girl. She fights me on EVERY SINGLE STUPID LITTLE THING and she's costing me a fortune on stupid stuff that untill recently hasn't been a problem.

  3. #3
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    If you blow a brake line, you usually displace the proportioning valve.You will need to do the calipers.If you depress the brake pedal 50 times you defeat the abs pump.Then bleed normally from furthest line from the master to the closest.....good luck.

  4. #4
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    Also with some GM vehicles I've found simply activating the ABS during a drive cycle (on gravel) will get any stubborn bubbles into the lines, so you can bleed them out.
    ....-Noltz
    '91 Frankenheep Edition. 4.0, 4" BDS, Richmond 8.8, 35" KM2's, Titan 12k, ... gone.
    '95 4Runner SR5. Air-Lift bags, OBA & 8K Winch, DD... gone.

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