So my '92 Custom Cruiser is blessed with ABS. Problem is, it doesn't work. After initial start-up, the light stays on. I am super unfamiliar with how this system works, but I believe it is a Bosch system, and I am assuming it's an all-wheel system. Correct me if I am wrong. I am still recovering from shoulder surgery, so unfortunately I cannot do anything with it as of yet, but as soon as I am able, I'd like to hit the ground running. What areas should I check? Where should I start?
Do the brakes work normally otherwise? Does it have a conventional power brake booster, or a hydraulic accumulator?
If its a slightly modern 4 channel system, and it was built by GM, two things- you probably don't really want it to work, and, at minimum, the brown wire running to the right front wheel speed sensor will be broken.
I was having the brake light issue with my '95 Roadmaster, also ABS. You can 'test' the system by lifting a wheel off the ground, turn the ignition on, and spin the tire by hand. You should hear the motor pump when that happens.
My problem turned out to be a rusted rear brake line, which was introducing air into the system and doing weird things to ABS. The line runs along the inside top of the frame rail, which is a very rust-prone area on these B-bodies. Replaced the line, bleed the system, and is good as new.
i've had early 90's gm's with functional ABS, i'd consider it a blessing it does not work. the only reason it's still in my impala is because the lines are mint otherwise it would be very gone.
however, if you want to repair i believe i have the 91 caprice factory service manual that you could borrow or i could take a picture of the repair flow chart. there is the pump, then there is a module, and then there are 3 sensors. 1 at each front wheel and one in the rear diff. the light can come on for a bad any one of these.
Yeah, brakes work normally otherwise, and it really doesn't get driven in inclement weather. I just hate having that light on. Looks like I have a Bosch 2U non-integral three channel system which works as Pat described. I'm willing to bet those front sensors are missing or completely shot.
I'd go with the fix I applied to the very mediocre ABS in the Jeep when it started to flake out: remove fuses and the bulb, then delete the physical ABS module when it's convenient to do so.
heck, I had a 2006 impala who's ABS I hated. You could feel it kick in on anything less than a gentle stop. Give me BMW's system, you never even know it is working, instead of the leg massage that GM gives you
In reply to mad_machine:
Well, I am not sure how much of a hand GM had in designing this system, but this early system was German. In origin anyway.
And now for the derp: I really want to avoid removing the system. It is after all a pretty rare car, and having components missing would constantly bug me.
Most of the early GM ABS problems were defective wheel speed sensors and brittle ABS wiring. Always go w/easy button visual inspection 1st. If rust is an issue, check for rust jacking at speed sensor mounting areas. Loose wheel bearings?
remove bulb, install into glovebox. no components missing. fixed. pretty sure i took the ABS bulb out when i did the cluster swap on the impala. and on my last dozen b bodies.
If it's anything like the ABS was on my 96 J body, anybody on this board should have no trouble outperforming it. I'd check for obvious stuff (mostly rust on the front sensors and tone rings and obvious broken wires) and then call it a day and pull the bulb. You likely need a big $ scanner to properly diagnose it.
I was serious about the brown wire to the right front abs sensor. I'd be willing to bet 85% of the GM abs problems I repaired in that era came down to a broken brown wire in the rf.
mad_machine wrote: heck, I had a 2006 impala who's ABS I hated. You could feel it kick in on anything less than a gentle stop. Give me BMW's system, you never even know it is working, instead of the leg massage that GM gives you
Don't say stuff like that. The factory engineers who frequent this board will tell you that you are wrong.
This sounds eerily familiar to the system in my 91 Saab 900.
Does your ABS light stay on, or is it intermittent?
In my car I don't get any dash lights unless I really get on the brake pedal- then I get the ABS and brake light. When I let off the pedal the lights go away.
From what I have researched this is due to the accumulator failing (as was already mentioned). I've been trying to find one locally to no avail. I even have a GM part number to reference that no one seems to be able to find 
I have yet to find the time or the weather to make it to a junk yard yet though.
Esoteric Nixon wrote: Yeah, brakes work normally otherwise, and it really doesn't get driven in inclement weather. I just hate having that light on. Looks like I have a Bosch 2U non-integral three channel system which works as Pat described. I'm willing to bet those front sensors are missing or completely shot.
In reply to paranoid_android74:
Mine stays on after the initial system check, and the brakes operate normally, just sans ABS. Though I am not positive, I am curious if your Saab has a Bosch system, as the Mercedes guys might be able to help.
Streetwise: I will take your suggestion into consideration once I feel comfortable enough to do some digging about. Rust isn't a huge concern, thankfully.
i remember Dad's 91 9C1 Caprice ABS. I've never had a brake pedal try to buck my foot off when activating like that on anything ever since. F that S. fuses and bulbs. Done.
This thread reminds me of the days when people that did not understand emission control systems plugged fuel tank vent lines, installed test pipes and attempted to get more hp out of low compression, overlapped valve engines by installing aftermarket intakes and bigger carbs.
outasite wrote: This thread reminds me of the days when people that did not understand emission control systems plugged fuel tank vent lines, installed test pipes and attempted to get more hp out of low compression, overlapped valve engines by installing aftermarket intakes and bigger carbs.
I'm guessing you never drive an early b-body Bosch abs. It shows.
Bobzilla wrote:outasite wrote: This thread reminds me of the days when people that did not understand emission control systems plugged fuel tank vent lines, installed test pipes and attempted to get more hp out of low compression, overlapped valve engines by installing aftermarket intakes and bigger carbs.I'm guessing you never drive an early b-body Bosch abs. It shows.
or any early-mid 90's gm system. my 94 suburban almost killed me by ABS'ing on a washboarded road downhill to a red light. i rolled right through with a trailer and ABS pumping away and came very close to getting plowed by a semi.
In reply to Bobzilla:
As an ASE mechanic/Automotive Tech Instructor I have driven, road tested/diagnosed, repaired/serviced, educated customers/students on this and other ABS systems. This system has a pump to replenish the fluid pressure that has been bled off to prevent brake lock up. Some systems allow the pedal to continue to move down as it bleeds off the pressure which alarms unknowing drivers as well.
Outasite, I've proven in back to back testing that the ABS in my 90s build Jeep is worthless. It activates needlessly on rough roads when you wouldn't actually lock up a tire (and it takes away a lot of braking power when it kicks in), and it activates with too little tire slip in the snow (with snow tires on), so you can generate far more braking force without locking a tire if you disable the ABS compared to what the ABS will allow.
ABS can be useful, but depending on the quality of the implementation, the other aspects of the braking system and the driver, it isn't necessarily better.
that is something I wish my Disco had.. a way to disable ABS in the snow. Snow is one of the few mediums where a locked tyre has been stopping ability as it "plows" through the snow, building up a wall ahead of it.
I know the controller is made by ATE, I am not sure about the rest of it. Or if they were ever affiliated with Bosch for that matter.
I'll be curious to read about what you find!
Esoteric Nixon wrote: In reply to paranoid_android74: Mine stays on after the initial system check, and the brakes operate normally, just sans ABS. Though I am not positive, I am curious if your Saab has a Bosch system, as the Mercedes guys might be able to help.
pull fuse, pull bulb...
The purpose of ABS is to "enhance" steering control during panic braking situations. I agree that it's operation and effectiveness depends on the road surface and weather conditions. GM provided a video to law enforcement agencies that purchased ABS equipped squads to demonstrate ABS operation because of accidents incurred by officers not understanding the purpose or operation. ABS cannot over come the laws of physics. A customer complained ABS did not operate properly since they had ran into the back of 2 cars on separate occasions at icy intersections. I guess they expected the trunk monkey to throw out an anchor to stop them on black ice.
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