Brake Issue 96 SS - Page 2 - Chevy Impala SS Forum
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post #11 of 18 (permalink) Old 05-31-2017, 05:43 AM Thread Starter
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Dealership says they used their equipment to bleed the ABS system and couldn't get it to bleed. Is this any indication that the ABS PUMP is dead?

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post #12 of 18 (permalink) Old 05-31-2017, 05:20 PM
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I keep hoping some one with a 1996 FSM will chime in on this.

The 94-95 is different from the 96 but they are a Bosch 2u system and should be similar.

If your engine/exhaust system is not too loud you can check the pump by ear.

Find a quiet downhill spot. Turn the car ignition to off. Then start the car and let it roll down the hill. At 4 MPH you should hear a short buzz of the ABS pump doing it's "Auto Test" (automatic test). If you are sure that you can turn and stop the car with the engine off. (no power steering and no power brakes) you might hear it better (key in run ). It sounds a bit like the fuel pump noise you get when you just turn the ignition switch to run. Buzz stop.

The ABS system does this every time you start the car and get it over 4 MPH (fwd or rev). If the pump or valves failed electronically The ABS light would be turned on and they would have a fail code to read.

The 1994 system with the correct dealer/aftermarket scan tool can go Mode 4 (misc. tests). Some one who knows what they are doing will be able to do the "Auto Test" with the car standing still. The valves can also be checked.

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Dealership says they used their equipment to bleed the ABS system and couldn't get it to bleed. Is this any indication that the ABS PUMP is dead?
No, the pump and valves are one unit and will be replaced as one piece. It would take pages to discuss how they decided "couldn't get it to bleed" The short question is why there is no ABS trouble codes if they were really unable to move the valves. To be fair there are failures like yours that do not trip a code.

Now for a short rant. I would not let these guys oil the chain on a pedal car. They do not seem to understand ABS systems. The ford system on my crown victoria does all the same things all the same way. I have had to read the Chevy FSM to make sure I am not confusing the two. My personal opinion is they do not know how to use the correct scan tool or do not have it. When you fix it get a report from the shop. Get a couple of 6 ft friends and have a talk with the dealership's general manager about getting some of your money back.

I would talk to some other repair shops and find one that show you the "Auto Test" triggered by the scan tool. I still think pressure gauge will lead you to replace the ABS module.

I almost never recommend "just tossing parts at a problem" In this case it might be cheaper for you to install a junk yard ABS module then have a shop that can do a ABS bleed finish the problem. You would know you were on the right track because the brake pedal would not go to the floor.

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post #13 of 18 (permalink) Old 06-01-2017, 06:23 AM
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Pedal slowly goes to the floor. If you pump it you have brake but as soon as you stop it goes to the floor. There are NO fluid leaks anywhere. No brake locking. No ABS light. Nothing. My brother and I bled the lines manually and this didn't help. So now the car is at a Chevy Dealership in Illinois and they have replaced the MS... twice. Now they are telling me the problem could be ABS related and that the parts are obsolete. There was a proportioning valve add done to the car by my Dad after he bought the car. They can't find this part either. This car has 17k on it. My Dad passed away in 2015 and left it to his family. I want to drive it. Show it. And enjoy it in his memory. I can't believe it can't be fixed and I'm at my wit's end.

Does anyone have any ideas? Can anyone point me to where I can get the proper proportioning valve for the car? Can the valve currently on the car be bled?

If anyone has experience with this issue please do offer me any direction you can.

Thank you very much.



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well if I had it I could fix it . pedal to floor is the master cylinder most all the time . This can be tested on the vehicle .you block off the 2 lines and if pedal stays high it is good.. 17K miles I doubt it is the ABS since these are in a protected area unlike my GM truck which I had to take apart and fix due to the fasteners rusting out on that aluminum body.

the ABS is possible the problem, I doubt it but if a valve is hung up it can do it. try to get the abs to cycle. drive the vehicle on a soft shoulder and hit the brakes so the abs cycles ..
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post #14 of 18 (permalink) Old 06-01-2017, 06:31 AM Thread Starter
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Dealership replaced the master cylinder twice. Didn't fix the problem.

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post #15 of 18 (permalink) Old 06-01-2017, 10:11 AM
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I'd suggest taking it to a local hot rod shop and having them remove
the ABS module completely and neatly flare the lines together.
Replacing the module with one from the junk yard as someone suggested is another idea, but
if you plan on keeping the car, it will fail again as these cars get closer to 30 years old.
Like the Vehicle Anti Theft System VATS that is giving everyone fits these days,
these abs systems were not designed to last that long.

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post #16 of 18 (permalink) Old 06-01-2017, 02:00 PM
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Dealership replaced the master cylinder twice. Didn't fix the problem.

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as I stated the master does not require removal to test it . plug the 2 lines and see if it holds the pedal high if so , no master problem. dealership did not test it, crooks !

drive vehicle on shoulder to activate the ABS .. with the right wheels slipping the left NOT the ABS will cycle the valves. 17K miles the ABS should not be damaged but a valve could be sticking or not sealing properly from lack of use.

also IMO YOU NEVER BRING A GM VEHICLE TO THE DEALERSHIP THIS OLD !!! Those repair techs probably were not even born , or were in the sand box school when this was produced .

cycle the ABS then bleed the system .. bring to a repair shop not a dealership , if your not up to it.

you may have a small leak it can happen . you sure the calipers and the bleed screws are not wet ?

this ever had a brake job done ,probably not @17K miles ...

was this stored outside or in a garage ? If it was outside could be steel lines leaking around the rear axle. driver side <<<,
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post #17 of 18 (permalink) Old 06-19-2019, 11:01 PM
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If anyone was wondering:


Quote:
Got the brake issue resolved also if anyone is still wondering. It was the ABS module. Got a rebuilt, kept the original. Brakes are great and the Imp is rollin'.
ImpalaGal14LTZ Post #8



https://www.impalassforum.com/vBulle...um-%2417k.html

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post #18 of 18 (permalink) Old 06-20-2019, 08:56 AM
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Huh - never connected the dots with this one being the same. Wasn't this the one where the dealer "replaced" the ABS module "twice" without fixing? If so, then still not as impressive as the warranty "replaced head gaskets" on my wife's Explorer that the dealer managed without even breaking the paint or seals anywhere.

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