Hi Guys,
I have a 93 g20 with abs brakes. It had bad brakes when i bought it about 5 weeks ago. This van only has 59,000 miles and has sat outside most of it's life. I have replaced both calipers and both wheel cylinders, master cylinder and all 3 rubber hoses. The system has been bled correctly. The problem is the abs light comes on and stays on after about 7-10 mph and will go out when i slow down. Wheel sensor? Trans tailshaft sensor?
Occasionally the brake light comes on and goes off, proportioning valve acting up?
I do have a good brake pedal though if feels hard to push, when you try an E stop it feels like you can't push it fast enough.
The booster is working, i unhooked it to check.
I would like to pull the fuse on the abs to try it without and see if it makes any difference but there is not one marked abs. Anyone know which one it is?
Any input would be appreciated.

thanks, Jim

speed censors..... my light has been on for yrs now ...it generally shows up after the censor on the allocation bar goes but you cant change that sensor unless you get the whole wire harness...as I say its been on for yrs now ...you have all the brakes you want its electronics that went....depends on how much it bothers you...

I can live without the abs, they haven't worked for years on my 94. If I could fix the abs easily I'd do it.
What would cause the slow brake pedal? When driving and you stomp the pedal it goes down with resistance almost like slow motion. The van stops quickly put won't lock up the tires, I do not here the abs kick in either(i'm sure it's not working). The pedal just dosen't have the right "feel". I've put two diff. master cylinders on with no change.
Jim

You still have ABS its the censor...thats why they dont lock up...the brake light is the allocation bar censor beginning to go out....the pedestal issue is most likely a bladder in your master cylinder leaking or it didnt get seated right after adding brake fluid...or at the other end... is there a oil mark on the inside of the tire ? May have a bad wheel cylinder...

Last night I replaced the rebuilt master cylinder with a brand new one not a rebuilt unit. Bled the system this evening - still the same slow pedal and no lockup. No leaks at wheel cylinders or calipers, all are new. I would like to try the brakes with no power to the abs system and see if that makes a difference. Is there an easy way to power the abs down? I was just going to take the cover off and unplug the harness, it's under the (floor) back seat passenger side.
Another question- how would I tell if the booster is going bad? I unhooked it and hooked it back up, seems to be working. I would think you would still get wheels to lockup even with a booster going bad.
Jim

Does ABS still stand for Anti-Lock Brake System? Should it prevent Locking it up?

your speed sensor in the trans.tailshaft sends signals the the ABS system and that could be going bad or is bad (mine had trans fluid in the wire plug when i pulled it off) causeing the system to set the light,you need to find a code reader and plug it into the computer on your van and read the codes and then clear them plus if someone in here can maybe direct you to chevy forums and there you should be able to read about this problem,the sensor number i replaced in my 93 is AC Delco #213194 price at rockauto.com $25 to $30 bucks this will give you a picture to look at,its easy to replace,one bolt and wire connector,plus the van does not have that many miles on it,i changed my brake fluid to synthetic fluid because it does not absorb water like conventional fluid, i bleed the system till it ran clear and drove it a week and did it again and no problems at all since then,you don't want to mess with that hydrolic unit under the van,it is very expensive $1300 to $1500 rebuilt,as other have said check for leaks, hope this can help you,joe.

Utah- The abs light is on and there is no lockup. If the light were off I would expect no lockup and would hope to hear the abs unit doin it's thing under the floor, but I have neither.

Gerywolf- I'll check for codes and take a look at that tailsensor tonight. Already put the synthetic in it.

Thanks guys

By slow brake pedal, do you mean it it moves slowly down when you stomp on it? If so, you may have to fix the ABS to get your brakes back where you want them as it would mean there is a line restriction or orifice that is preventing full pressure from getting to the wheels. The only other alternative would be to replumb new lines and bypass the ABS unit. If you can figure out which circuit has the restriction, front or back, you may be able to force the solenoid in the ABS unit for that circuit to full open.

Thanks Bullet, I think your onto something, it makes sense.
I stopped at O'Riley auto parts on the way home from work to see if they could pull codes from the abs but their reader will only go back to 1996 and will only pull engine codes. So I stopped at my local garage they said ok bring it by Monday, It'll only be 73.00 to diagnose. Nice. If I weren't already bald I'd be pullin my hair out! (well i could but i can't reach that part of my back)
I have buddy I grew up with that owns his own shop but is 125 mile away. I'll spend that 73.00 (and then some on) gas and go see him.
I'd like to pull codes before I start replacing parts, I have a 94 van and truck I can swap parts from.

Yep, I've learned the hard way, better to spend the time zeroing in on what's wrong than just start swapping parts hoping to get it right. A lot of times you end up creating new problems too. Sounds like you are onto it tho'. Keep us posted.

Talked to my buddy over the weekend, he dosen't have the software for reading the abs codes for something as mundane as a gmc. If I had a vw porsche bmw jag mercedes he could fix me up. Figures!

I pulled the cover off the abs unit tonite, looks like it would be pretty easy to pipe around it. I soaked the fittings with pb blaster just in case. Taped on the solonoids with small hammer - can't hurt at this point.

I'll check at another shop here in town and see if they can read the codes.

Update on the brakes-
I removed the cover on ABS unit, somebody had been there before, one of the solenoids was unplugged, sooo I removed it and piped around it. Brakes are better but still no lockup. The booster holds good vacumn I replaced the check valve anyway. no difference. While I was under the van I ran down all the lines and found no pinches or kinks.
The only thing I haven't touched is the proportioning valve. This van sat for quite a while before I bought it, the old brake fluid was nasty. Could that valve be stuck and causing a restriction- not letting full pressure get to the front brakes?

The proportion valve can stick alittle,look at it and in the front of it there should be a little/small rubber boot you can just pop off and you'll see a small rod in the center of it,if i remember right you can push it in or pull it out,i believe in is the right direction and it should move a small amount,if does not move then it is stuck,you can have someone in the van push the brake pedal with the van running and you look at the rod and it should move a small bit when they pump the brake pedal,if you can see it move by it's self it should be ok,maybe you'll get lucky and it will move,if not try moving yourself,if does not move then it is stuck and that could be your problem, you can get them out of the junk yard,i think they are expensive new,also check the rubber hoses as they could have collasped on the inside and not allow the fluid to get to the calipers, as for the brakes locking up you don't want that to happen because you could lose control of your van and wreck it or slide off the road or hit someone else and you don't want that to happen SAFETY FIRST !!,joe.

Thanks Joe,
I'll check the rod on the proportioning valve tomorrow I almost hope it's bad and the cause of my problem. All three rubber hoses are new so I know there're good. I'm an old school guy, don't really need ABS brakes, they,re fine if they work but,I've driven for years in cars without them. The ABS unit in this van was deffinately screwed up, I'm better off without it. Just another thing the PO didn,t tell me about!
I just want to be able to make an E-stop and be able to lock the wheels. When I stomp the pedal the van slows very quickly but fails to lock. The brakes feel normal just missing that last little bit at the end of the pedal travel that would lock the wheels. It,s difficult to describe.

OK - I checked and the little rod on the prportioning valve, it moves out about 3/16" with the van running and the brake pedal pushed. Should it move more than that?

Jim that is about all it should move,now atleast you know it is not stuck and moves on it's own,thats good,are you still haveing problems with the brakes?,you said the fluid was bad before and you changed it,maybe bleed them again and see if that helps,i was talking to a friend and he said they use to have alitle clip that you could use to hold that rod out while you bled the front calipers and that allowed the fluid to pass thru the valve better or you could hold that rod yourself but on mine i didn't do it that way,i just bleed them with my son pressing on the brake pedal and that worked fine my fluid was black and i bleed atleast a quart of fluid thru the system and they have been fine.joe

Have you replaced the rubber lines in the brake system? They can cause all kinds of weird happenings. They break down on the inside and I've had them lock calipers, cause the vehicle to dart one way or another, etc. Something to consider while you're in there.

As for getting them to lock up and slide, ABS is supposed to prevent that from happening. I know you've bypassed the one circuit but the other may still be functioning. I have never gotten my van to lock all four. It will lock the front on a hard braking but I've never locked the back ones. Weight distribution has a lot to do with it and the quality of the brake hardware does too. I've had 2 cases where I had defective brakes out of the box. On my '67 van, it quickly got to where it pulled so hard to the right when I even moderately applied the brakes that it was dangerous to drive. The wheel cylinders, some of the hard parts, and the shoes were new. I worked and worked and finally in desperation, took the hoes back and had them warranty them and that fixed the problem. I also had a Jeep Cherokee that wouldn't lock. I set the rear shoes up so tight you couldn't even budge the wheel with it on stands. 30mph and hard stomp of the pedal and it just kind of came to a much too long stop. I replaced the shoes (they were new to begin with) and it immediately locked them on the same 30mph stomp the pedal application.

Problems like this can make you bonkers. Think it all through logically before spending hard earned dough.

Well here's whats been done so far-
New master clyinder (not rebuilt)
New wheel cylinders
New (rebuilt) calipers
New rubber hoses, 2 front, 1 rear
New vacumn booster check valve
New rotors, drums turned
New pads and shoes

The shoes and pads are autozone house brand. Maybe I need to upgrade to Raybestes, or another name brand. Ceramics? Any suggestions?

The ABS unit has been removed from the van competely (anybody need a boat anchor?) and the lines plumbed back in. It was definately messed with before I bought the van. Never could get it to work.
I have bled the system 4 times, the brake fliud runs nice and clean.

I sure appreciate all the help guys. I've done lots of brake jobs over the years, had problems here and there but nothing like this.

I had a couple GM vans that wouldnt lock up the front wheels. All the weight of the engine, passengers and front end is on the front wheels. You're more likely to get the rears to lock up. either way, the fastest way to stop is just before they lock, so the fact that they wont may just save your butt one day.

You can upgrade but I don't know if ceramics are in order. I did put ceramics on my Astro simply because I tow at max GVW and sometimes more. Ceramics work great but they eat rotors like the cookie monster goes for chips ahoy. Brake rotors on vehicles that come with ceramics are harder and so endure better. Was there any improvement at all once you removed the ABS box?

NO CERAMIC's unless you have a good supply of rotors....I run Raybestos in both my G30's...

OK- Finally got back to the brakes, I just bought a set of Wagner shoes and pads. Not ceramic, but still higher end. Will get them installed tonight.

To answer your question, Yes there was a big difference after the ABS unit was removed. The pedal felt more "normal" but I still can't lock the wheels. The van will slow very quickly but not lock up.

New pads and shoes are on, took a test drive,BIG difference. The brakes will almost lockup, I'm sure It'll get better as they wear in. Takin' a little road trip this weekend so we'll find out. Feel a lot more confident driving.

Excellent, glad you had some success.

They Work!!!! I can lock em up if I need to now. I put a couple hundred miles on over the weekend got the shoes and pads broke in. Went to my daughters(hour and a half away) to work on their house and fixed their toilet, I always get the dirty jobs! Also flat towed my Nash to a car show Sunday. The Van ran great in the heat and the brakes worked perfectly!

Lesson learned- Don't use house brand brake shoes. I've never had problems in the past but I will never use them again!
Thanks for all the help guys.