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Discussion Starter #1
Hey, i have a 1996 G20, with abs brakes.

my problem is that my brakes tend to "lock up"

when I say "lock up" i mean exactly this:
when I press the brake, i feel some sort of "metal thing" pushing back on the brake pedal and not letting me push down to stop. If i try and push harder, the "metal thing" pushing back seems to lock the brakes even more. when this happens the brakes go out completely until the car reaches a dead stop, basicaly after I pull the e-brake.

80% of the time this happens during rain/snow (moisture weather). Also, when my brake pads run low, it gets worse.

At first I thought my calipers were locking, but it would be odd that both calipers are locking at the same time. So i'm almost certain this problem has something to do with the ABS, but i'm not sure exactly how to fix this.

Any help is greatly appreciated.

thanks.
 

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its either the abs or the booster line. the abs will feel like a vibrating mess and the pedal pressure will vary when this happens the car should stop normal because you are not sliding. if its the booster line in cols weather it will do it because theres less vacuum. another possibility is brake fade since you mentioned it happens with bad pads. but from the way you describing it its either abs or bad booster line. if you could desribe it better thatd be helpful.
 

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Discussion Starter #4
Before If I had fresh pads all around, and it was a nice day outside, I usually wouldn't have any problems. If I was running low on pads, or it was rain/snow outside the problem would occur more frequently.

As of now, the problem is happening no matter what weather outside, it is COLD (maybe some sort of condensation is occuring? though, i doubt it)

I just checked my brake pads and they all have a LOT of meat on them, I thought I was running low since the problem had begun occuring more frequently.

*I don't press the brake pedal hard, it doesn't seem to be working as its supposed to.

Basicly, it happens like this. When I'm trying to brake ( i usually down shift first) so this problem is almost always in low speeds (0-15mph.) then, when I go to push my pedal...well, you know how the first half inch of your brake pedal seems a little weak, almost as if it was just play in the pedal, though i know it's not.. I feel the "vibrating mess" coming ON EXACTLY then, and now i've learned to back off the brakes and use the E-brake, but if I continue to use my brake pedal as I feel it coming on, I will lose all controll of the brakes and the car will just keep rolling, untill I reach a dead stop(but obviously I use my e-brake to get to a dead stop). that is when they come back to normal.

I'm trying to search for a "booster line" I can't find much or any info on it, so any other info on what a booster line is would help.

thanks.
 

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the vacuum hose running from the intake manifold to the booster on the back of the master cyliner is the booster line but if your getting the "vibrating mess" then there is something wrong with your abs. try cleaning all the abs sensors and running a diognostic test on the abs system. my moms exploder had this i just remembered the ton rings were all rusty and blah. i would check the sensors on each wheel and the tone rings. check the resistance on the sensors (i don not know the specs) and check all wires. if you can barrow a genisys look at the wave patterns for the abs system see if they are off at all. but it is definetly abs. also another thing to do is clean the sensors and the tone rings with a good brake celaner. and the sensors have to be within a certain distance from the tone ring. the computer is getting a false reading that you are sliding.
 

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Discussion Starter #6
thanks, i'm going to try and diagnose this now.

one question though.. the ABS light has never come on, does this raise any concern?
 

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not really, the computer thinks the ABS is working properly so no light, I'd be willing to bet one or more of your rings has cracked and come loose from the axel. this causes them to move at differt rates than your axel and the system thinks your sliding. in addition the moisture would help them spin or not spin with the axel. spray em off with brake cleaner and see if you can spin them by hand. i'm not sure what the repllacement procedure is but if its a front sensor they are pressed on and most likely you will need a new axel
 

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Discussion Starter #9
I'm not exactly sure how the ABS sensors are placed, but i'm gonna take a look and see what i can find out in the morning..

but, you say I need to get new axel's ?

even if i JUST replaced them..?
 

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well if its a sensore then your abs light should go off, if its the ring on the axel that the sensor reads then older ABS sensors werent programed to detect a slipping ring.
behind your wheel hubs there is a ring mounted to the axel, its suppose to be firmly attached to the axel so it moves when the axel moves and stops when the axel stops. it looks like it has evenly spacednotches on it and thats what the sensor reads as they pass it. the sensor will be a little black box with a dark plastic window and a wire going into it. the rings should go all the way around the axel and you shouldnt be able to spin them. if one is just sping, most likely cause there is a crack in it, try apoxying it back in place. check both front and back
 

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if you can get your hands on new rings and take your axel to a shop that can press them on. usually when one goes you just replace the axel on most cars because the labor isnt worth putting new rings on. try the apoxy. and clean the rings and sensors
 

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Pizdeet kak Trotsky
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I ain't gotta clue whats going on here, but this I do know ......

If your calipers were malfunctioning they wouldn't work at all & could be leaking fluid

It is possible for the abs sensors to get a coating of metal bits & bats from here & there & may need cleaning ..... Don't try & take the sensors off the front to try & clean them they will fall to pieces (They are bolted in) Just get to the sensor side of the probe & clean em with (Vacc & Q tip) Brake cleaner, Carb cleaner etc etc..... I found the rear sensors didn't get stuck so readily ....... I'll let you work that one out ....

Tyres/Tires ...... Umm even if they are above the wear markers they can start to slide under braking with amazing ease.......
 

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Pizdeet kak Trotsky
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echandler said:
what happens if you disconnect the abs pump?
The abs don't work ;)
 

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The ABS computer tests your ABS system every time you start the car and go over 6-7 mph. You will experience this is a somewhat unpleasant vibration in the brake pedal for a few seconds. If there is a problem with the ABS and the ABS computer isn't happy with it, it shuts the ABS system off and defaults to regular non-ABS brakes. I imagine if you unplug the fuse or the connector for the ABS pump, it will default to regular brakes. I would want to do that first to be sure your brakes are working OK without the ABS. If they work OK at that point, then you know it is the ABS system that is a problem.

I'm not exactly sure what your symptoms are-- If you are in a level dry parking lot and get it over 10-15 mph and step on the brakes, you do not slow down and stop? If you don't use your ebrake, the car keeps going forward? If your ABS is activated, you will get the vibration which is the system quickly sensing and pulsing each wheel's brakes depending on differences in each wheel's rotating speed. See here:

http://auto.howstuffworks.com/anti-lock-brake.htm

The toothed wheel sensor ring is basically pressed on to the hub- if it is loose it should be replaced. The wheel sensors are little electromagnetic cylinders that poke thru the hub from the back (wire out the back) and have a diamond shaped pickup that sticks out very close to the sensor ring on the brake side. You can't get to them or the ring without pulling the wheel and rotor. If there is a problem with the wheel sensors, your ABS light will stay on, and a code will be generated (which you can read- instructions in other ABS posts). Does your ABS lite come on at start up, then shut off after a few seconds (ABS lite works OK?)??

It also occurs to me that you said you replaced some axles? I wonder if they put in some that didn't even have the sensor rings- I see these on eBay all the time and have had autoparts stores get them in without the rings. I don't know what the ABS system would do if there were no rings...
 

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my bad I figured the sensors and rings would be visable from the back of the hub.
as far as not having rings on your axles or haveing them come loose, most earlier ABS systems would just see it as wheel skid
 
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