Open question to Bob Scopatz Re: ABS failure

[wheresjim]

I wanted to clarify which parts you said caused your total ABS failure. I seem to recall you described it as a "waterfall" effect where a switch went, which caused a relay to go and then the pump and so on...<P>Do you know what parts and in which order they failed? <P>I think this info would be very useful to gauge if our vehicles are imminently dangerous.<p>[This message has been edited by wheresjim (edited 06-13-2000).]

[Guest]

According to my mechanic (at Buick dealer), the sensor must've been the first thing to go because I never got any dash warning lights for Brake or ABS while they slowly died. He checked and the lights were still working, so his conclusion is that the sensors were bad. That, or probably the computer.<P>Next in line, a switch died. This is the switch that controls the motor that powers the pump, ... The dead switch meant that the pump ran constantly, until it burned out.<P>When it burned out, it probably took other components with it, but most definitely he thought that the accummulator was gone (if I remember correctly).<P>He also felt strongly that once he got all the other stuff working, he would find that the computer was messed up.<P>That's all I can recall. Hope it makes sense and helps out in some way.<BR>

[Guest wally888]

If you had total failure- not even manual braking as when the ignition switch is off and the accumulator has lost all pressure and the pedal doesn't get hard but goes to the floor<BR>seems you had a master cylinder failure? or fluid loss?<BR>Comments?<p>[This message has been edited by wally888 (edited 06-14-2000).]

[Guest]

I had what some have called "hard pedal." In my case, I would call it impossible pedal. The pedal was solid. Didn't go to the floor. Didn't budge. My wife is quite petite, so perhaps it was just that she lacks the leg strength to get braking power out of this situation, but I suspect not. I suspect the pedal was locked in the up position by some means not thought of by the designers of this system.<P>My master cylinder checked out fine. That was the sad irony of all this. I had a perfectly functional regular braking system that all the special ABS and electronics kept me from actually accessing.<P>I call that bad design. In failure mode, the thing should be designed to either not start moving in the first place, or to die a gradual death, like the old reliable hydraulic systems used to. (unless someone cut your brake line, of course).<P>I'd never seen anything like it. I figured it was 1 in a million. Turns out its more like 40 in 40,000 (or however many Reattas there were). I don't like those odds.<BR>

[Guest]

HARD PEDAL, NO BRAKES! IT ALL STARTS FROM THE RESERVOIR BEING OVER FILLED DUE TO NOT PUMPING THE BRAKES 20 TIMES AS INDICATED ON THE CYLINDER BEFORE FILLING. I BELIEVE IF YOU HAD LOOKED AT THE RESERVOIR AFTER THIS HAPPENED THAT THE RESERVOIR WOULD HAVE BEEN COMPLETELY FULL, AND IF YOU HAD REMOVED THE CAP THAT IT WOULD HAVE OVERFLOWED. REMOVING THE EXCESS FLUID MAY TEMPORARILY SOLVE THE PROBLEM, BUT THE PROBLEM WILL STILL BE THERE. IT SEEMS THAT ONCE THIS HAPPENS IT DOES CAUSE SOME TYPE OF CYLINDER DAMAGE. IF YOU EVER HAVE YOUR BRAKES WORKED ON, MAKE SURE THEY COMPLY WITH THE INSTRUCTION. I HAD THIS PROBLEM TWICE TEN YEARS AGO. I ALLOW NO ONE TO FILL MY MASTER CYLINDER. IF I COULD PUT A LOCK AND KEY ON IT, I WOULD.

[wheresjim]

Thanks, Bob.<P>I know that this info will help me, I hope it helps the others as well.<P>Jim.

[Guest]

As far as I can recall, my brakes were never worked on this car. I don't think any fluid was ever added to the master cylinder. I don't know if that's a good thing or not, with a car that was 9 years old and had 138K miles on it at the time. But, this was the first time I'd had any work on the brake system, per se. There was a repair several years before (like around 5) because I went over a dip and crunched some portion of the ABS on the other side. Either that or the shock of landing on the other side with the brakes and ABS engaged tore something up. At any rate,there was some module I had to pay for. Never really had a problem with the brakes or braking power even with that damage. Then, all of a sudden, NOTHING.<BR>

[Guest]

hi bob.<BR>got a 90 reatta that lost power brakes in middle of stop/go traffic, 97deg weather. no warning, no lights. gots hard pedal about 1/2 way down and able to stop car with leg power, just no power brakes. replaced pump motor relay, checked ALL fuses, and relays...no joy. pedal will not go all the way to the floor, still no lights on, just no power brakes. dumb dirtyword thing gots the best of me. grouchyandugly@nefcom.net

[Guest wally888]

Seems I have the light on(anti lock) but no brake problems!Been this way for a year,hope to clear problem this week.<BR> If a hydraulic diagram were available for this system I believe most problems would be understood and solved simply.<BR> I suspect when there is not enough pressure to have normal breaking either the pump has failed partially or completely or the pressure sensor has failed and doesn't tell the pump to come on.Possibly the relay activated by the pressure sensor may have failed and no signal(voltage) was sent to pump.<BR> If the accumulator fails I suspect you would still have some hydraulic assist till you pumped the brakes a 2nd or 3rd time.<BR> The anti skid function and system are almost independant of the main brake system.If it fails it should only effect straight stopping not cause other components to fail.<BR> The more I read of big repair bills,the more suspect I am about rip offs or the mechanic just removing and replacing till the problem goes away. If i have a problem in the future I am certain I will take car to dealer and make certain the mechanic understands the system!<BR> Note I used ,I suspect" most of the time.Would appreciate any explanations or errors.<P>------------------<BR>Definition of an expert: An ordinary guy called in from out of town!

[TheBlackMoon]

Wally, <BR>I have to say that I've begun to suspect the same thing. I was taught much by mechanics (though I don't consider myself an expert in any sense of the word), and if nothing else, I learned just how vulnerable we are, simply because we just don't know.

[Guest]

I just noted a reply that stated the "hard pedal"(no power assit)brake failure can be the result of overfilling. <P>I HAD BRAKE PADS PUT ON MY CAR 10 DAYS PRIOR TO THIS FAILURE AND IN LOOKING THE CAR OVER AFTER THE FAILURE I DID NOTE THAT THE RESERVOIR WAS TOO FULL,ALMOST TO THE CAP. <P>HOW COULD THE OVERRILL BE PROVEN? i'VE BEEN<BR>QUOTED 3,500 TO REPAIR BUT STILL LOOKING INTO<BR>IT.

[Guest]

FOLLOW THE INSTRUCTION ON THE FRONT OF THE RESERVIOR NOW, AND SEE HOW HIGH IT GETS AFTER THE PUMPING OF THE PEDAL. IF ITS ABOVE THE LINE THEY DIDN'T FOLLOW INSTRUCTION<BR> <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by ladyreatta:<BR><B>I just noted a reply that stated the "hard pedal"(no power assit)brake failure can be the result of overfilling. <P>I HAD BRAKE PADS PUT ON MY CAR 10 DAYS PRIOR TO THIS FAILURE AND IN LOOKING THE CAR OVER AFTER THE FAILURE I DID NOTE THAT THE RESERVOIR WAS TOO FULL,ALMOST TO THE CAP. <P>HOW COULD THE OVERRILL BE PROVEN? i'VE BEEN<BR>QUOTED 3,500 TO REPAIR BUT STILL LOOKING INTO<BR>IT.</B><HR></BLOCKQUOTE><P>

[Guest]

Just bringing this to the front (current) topic page so that the GM folks can find it more quickly. See note from me about conversation with GM.