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Major pulsing in the brakes


Brodizzle83
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I was driving my '96 GP SE this past summer and the brakes were pulsating pretty good, and it got to the point where it was scary to drive. It almost feels like a severely warped rotor, but I'm almost positive that's not the case. I know the rear brake line had a small hole in it that I honestly forgot to replace. If the hole got bigger, could that cause my rear brakes to pulsate terribly bad? It was so bad that it kept tripping the ABS and the traction light came on. Just trying to troubleshoot before I start replacing things. I also have a blown rear strut that I'm replacing...actually, both are getting replaced. But I checked the rear brakes and they look fine. I do have new rotors and pads though since I was going to replace them at some point.

 

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Sounds more like a speed sensor that's failing (ie: the ABS computer isn't receiving a signal that the wheel is moving, so its trying to apply anti-lock functionality to the brake), rather than something to do with the brake line(s).  Having said that, obviously the brake line needs to be serviced.  

Can you (temporarily) disconnect the ABS unit's power wiring, and report whether or not the problem duplicates itself?  

Edited by pitzel
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Sounds more like a speed sensor that's failing (ie: the ABS computer isn't receiving a signal that the wheel is moving, so its trying to apply anti-lock functionality to the brake), rather than something to do with the brake line(s).  Having said that, obviously the brake line needs to be serviced.  
Can you (temporarily) disconnect the ABS unit's power wiring, and report whether or not the problem duplicates itself?  
I actually looked on RockAuto for a speed sensor and I'm not seeing one. Does my '96 even have a speed sensor? Or is it part of the ABS system?

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My 99 Lomina didn't come equipped with ABS... My friend is Wholesale Parts Manager at a large Chevy Dealer and said ALL Luminas came with ABS... When I showed him mine he freaked... All the mechanix were standing around the car scratching their heads saying they had never seen or heard of such a thing... 

Not saying that's your case... Just saying some cars were NOT so equipped...

Tom B...

I suppose a bad line could cause problems...

Edited by walterdude
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5 hours ago, Brodizzle83 said:

I actually looked on RockAuto for a speed sensor and I'm not seeing one. Does my '96 even have a speed sensor? Or is it part of the ABS system?

Sent from my Pixel 3 XL using Tapatalk
 

The speed sensor is built into the rear wheel bearing assembly, so if that's your issue (and I'm not offering a diagnosis), then you'd need to replace the entire bearing/speed sensor assembly as a unit.  Unlike the front sensor and bearing, I don't believe the rears are separable.

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43 minutes ago, walterdude said:

My 99 Lomina didn't come equipped with ABS... My friend is Wholesale Parts Manager at a large Chevy Dealer and said ALL Luminas came with ABS... When I showed him mine he freaked... All the mechanix were standing around the car scratching their heads saying they had never seen or heard of such a thing... 

Sounds like something that might've been done for a large fleet order in a locale without particularly severe weather to shave $500 off the price.   But such cars wouldn't have been handled through the dealers.  I once had a Ford truck at work that was like that, completely stripped of even the most basic options that would've been standard equipment in retail-sold vehicles.  By the time 1999 rolled around, I suspect the only buyers of Luminas were institutional fleets.  

Edited by pitzel
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Yeah,,, it was some kind of a fleet car... Some Insurance Exec drove it in Fla... I understand that most 99 and 00 models were sold as fleet cars... My Mother bought it from my friend at the dealer... It had around 10K on it... I inherited when she died with about 15k And junked it with over 250k due to rusted out frame... Never stranded me!!!

Tom B...

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