Brake problem

[ct9a]

I posted this in the Suburban section, but maybe it wasn't getting enough exposure since no one responded.

I've never heard of this problem before, but when I push the brake pedal down, it takes for ever to come up on its own and in the mean time, the brakes are locked up. I can put my foot under the pedal and lift it back up, but it takes some effort to do that and my shin muscles are sore today from driving yesterday. Any thoughts?

[ct9a]

Ok, well I bled all 4 corners yesterday and still have the problem. I tried to bleed the ABS system, but to no avail, no fluid would come out of the bleeder nipples.

I forgot to add that my ABS light is on. I was told by someone to check the wheel cylinders in the drums to make sure they weren't leaking, and a quick visual inspection showed no leaks (I didn't pull the boots off though). I haven't seen any leaks in the hydraulic system from MC back.

Someone help me please.

[zippy]

Ok, well I bled all 4 corners yesterday and still have the problem. I tried to bleed the ABS system, but to no avail, no fluid would come out of the bleeder nipples.

I forgot to add that my ABS light is on. I was told by someone to check the wheel cylinders in the drums to make sure they weren't leaking, and a quick visual inspection showed no leaks (I didn't pull the boots off though). I haven't seen any leaks in the hydraulic system from MC back.


It seem, there are only two possible causes for your problem: there is a restriction in your hydraulic system preventing the fluid's return, or there is an actual mechanical binding preventing the pedal's normal return.

While you were doing the actual bleeding, did the problem persist? Did you bleed the ABS "by the book"? My gut feeling is that something is hung up in your ABS box. The warning light seems to confirm this. First things first, you need to pull the code on the ABS alert... get a manual and count the flashes. With some luck, it may give you a pretty good idea where to start looking.

Unless you're competent mucking about with the ABS (I'm surely not) I'd be looking for an expert. Sadly, this may be one of those situations where your wallet is gonna take a big bite.

Good luck, ct9a

[ct9a]

Thanks for the tips.

To answer your questions, no, the pedal seemed fine when bleeding the brakes. In fact, the pedal is fine when I start the motor up and just sit there pumping it. The second the truck starts moving is when the problem starts.

No I did not bleed the ABS system "by the book". Unfortunately, I'm not sure how that's done. I figured that the procedure was the same as the brakes, just pump, hold, open nipple, close nipple, repeat.

What manual are you speaking of? Would a Chilton's have what I need, or do I need to get my hands on an actual GM service manual? I didn't know GM's flashed codes on the dash, learning something new everyday.

[zippy]

You haven't mentioned the year of your truck... earlier models allow you to pull the codes without a scanner. It's a simple method of knowing when and where to jump the data port connectors and count the flashes. Then you look up the number(s) in the appropriate table in your Chiltons.
Newer models (since mid-90s) with ODB-II require the use of a scanner. The numbers are too complex to count flashes, but you get more comprehensive info.
This club's forums have links to trouble codes, just click the search button at the top of the page.

[ct9a]

Oh, sorry. It's a '94 Suburban K1500.

I replaced all 3 soft brake lines today and it seems to have solved the problem...... almost. The pedal now returns normally when I come to a complete stop, however, it still sticks when I'm just slowing down to make a turn. The pedal is pretty squishy, so I'm going to try and bleed it again tomorrow. If this doesn't work, would the master cylinder be the next part I shotgun at the truck?

[zippy]

I still think you should first address the ABS trouble code. Your '94 can be done without a scanner, just follow the procedure described in your Chilton's or in this club's forums. Get out a paper clip and count the flashes. To clear the error codes, just disconnect the battery for a while, if they come back on, then the problem hasn't been corrected. Back in January, I wrote...
I couldn't get the ABS light to clear in my '93 'Burb. I'd just done new rotors and calipers, what could be wrong? I eventually came to the realization that the parts house had given me an unmatched 'pair' of new rotors: one with the toothed sensor ring and one without. I'd failed to notice the difference during installation, but the internal code cops didn't.

[collinsperformance]

i agree run the ABS code check and see what it thinks is the issue...mike

[ct9a]

Ok, so I tried to pull the codes out, by jumping A to B on the port under the dash. The SES light just flashed 12 at me over and over. From what I read, 12 means nothing is wrong. I should have also mentioned that the ABS light seems to reset itself (soft code?) every time the truck is turned off. It only comes on after the first time I brake after getting the truck rolling. Is there a different port that I need to be jumping? I couldn't find any data pertaining to the ABS trouble codes, but only engine and tranny codes.

[zippy]

Ok, so I tried to pull the codes out, by jumping A to B on the port under the dash. The SES light just flashed 12 at me over and over. From what I read, 12 means nothing is wrong. I should have also mentioned that the ABS light seems to reset itself (soft code?) every time the truck is turned off. It only comes on after the first time I brake after getting the truck rolling. Is there a different port that I need to be jumping? I couldn't find any data pertaining to the ABS trouble codes, but only engine and tranny codes.
You're on the right track, now you know the procedure; but, you took a wrong turn. Yes, repetitive code 12 means there are no problems for the circuit in question. Unfortunately, you jumped Terminal-B... for Anti-Lock trouble codes, you need to jump Terminal-H to ground or to Terminal-A. Read the code from the flashing Anti-Lock light. Since the trouble light comes only after you're rolling, you know the system is working after the static start-up check.
Keep in mind, just because there is a code on something. Say you get a Code-21, don't run out and buy a new right front speed sensor. Instead, start at the sensor and work to the computer making sure each of the connector points is okay. To the computer, a bad connection is the same a as faulty sensor; but, much cheaper to repair.

Here are the OBD-1 codes for the four wheel anti-lock brake system:
http://img258.imageshack.us/img258/4535/abscodescr1.jpg

[trailblazer58]

How old is your suburban? And, not only how old but has it been sitting a long time without use? I have heard of the brake fluid getting so old from sitting that it jells up. I'm not sure if this would cause that symptom but the way you can tell is to open your reservoir and suction some of the fluid out to see what kind of shape it's in. I had a brake guy tell me it can get sort of moldy and this will cause it to jell up. Seems like this could cause that symptom but again it's just a wild guess! If true you would need to clean out and flush your brake system. Shops can do this too for a charge of course.

[collinsperformance]

i learned the hard way i use to think if it has fluide you ar ok no reason to swap fluide out, wrong! hydrolic (brake) fluid like to pull in moisture this is what causes the gum up. you should swap out the brake fluid every 2 years or 20,000 miles. most of the strange things i took for normal are now gone and the brakes work great. .....mike

[ct9a]

How old is your suburban? And, not only how old but has it been sitting a long time without use? I have heard of the brake fluid getting so old from sitting that it jells up. I'm not sure if this would cause that symptom but the way you can tell is to open your reservoir and suction some of the fluid out to see what kind of shape it's in. I had a brake guy tell me it can get sort of moldy and this will cause it to jell up. Seems like this could cause that symptom but again it's just a wild guess! If true you would need to clean out and flush your brake system. Shops can do this too for a charge of course.

This is actually one of the first things that I checked out. I just got the truck from a friend that used it as a daily driver, so it hadn't been sitting. The inside of the reservoir looked fine as did the fluid that I was getting out of it when I was bleeding all four corners.

[ct9a]

You're on the right track, now you know the procedure; but, you took a wrong turn. Yes, repetitive code 12 means there are no problems for the circuit in question. Unfortunately, you jumped Terminal-B... for Anti-Lock trouble codes, you need to jump Terminal-H to ground or to Terminal-A. Read the code from the flashing Anti-Lock light. Since the trouble light comes only after you're rolling, you know the system is working after the static start-up check.
Keep in mind, just because there is a code on something. Say you get a Code-21, don't run out and buy a new right front speed sensor. Instead, start at the sensor and work to the computer making sure each of the connector points is okay. To the computer, a bad connection is the same a as faulty sensor; but, much cheaper to repair.

Here are the OBD-1 codes for the four wheel anti-lock brake system:
http://img258.imageshack.us/img258/4535/abscodescr1.jpg

This is awesome information. Thanks. Now I have something to do in the morning.:great:

[ct9a]

Holy sh!t!! I got a whole list of codes from the ABS. Here they are in the order they came out:

51 - Control valves
52 - Control valves
12 - ???
45 - Control valves
65 - Open or shorted pump motor relay
67 - Open motor circuit or shorted BPMV circuit
46 - Control valves
41 - Control valves
42 - Control valves

I'm going to go start looking for bad connections or corroded wires. What are the control valves and where are they located? Are they all part of the unit that has all of the brake lines going into it? If so, maybe there's just one short causing all of this, or maybe just that one part that needs to be replaced?

[zippy]

Holy sh!t!! I got a whole list of codes from the ABS. Here they are in the order they came out:

51 - Control valves
52 - Control valves
12 - ???
45 - Control valves
65 - Open or shorted pump motor relay
67 - Open motor circuit or shorted BPMV circuit
46 - Control valves
41 - Control valves
42 - Control valves

I'm going to go start looking for bad connections or corroded wires. What are the control valves and where are they located? Are they all part of the unit that has all of the brake lines going into it? If so, maybe there's just one short causing all of this, or maybe just that one part that needs to be replaced?

Okay, the easy part first:
Code-12 is the reference (or stop/start) code it brackets the trouble codes. Alone it's the okay code. Typically, you want to see two 12s so you know you got everything in between.

Yes, the control valves are in that unit with all of the brake lines going into it. Also, there are many electrical connectors, too. You're right, start looking for bad connections.

Take your time and do the best job you can. If you recall, I mentioned early on, the unit can rip a hole in your wallet. Treat it like it was made of gold: Chilton's says it's not consumer serviceable and my local NAPA shows a list price for a re-built unit at $694.00 plus a $313.00 core charge!!! :shocked: I wouldn't think about shelling out that kind of money without first having an ABS expert have a look. Good luck!!

[ct9a]

Ok, I've checked as many wires and connections that I could possibly find and found nothing out of the ordinary.

I did a little more playing around with the truck and here are two new things that I have found with the brake system.

1. When the brake pedal is stuck to the floor, it's mainly the front brakes that are locked up. I can't move the wheels by hand at all once the truck is in the air. The rears, are tight, but not locked. I can still spin the wheels, just not as freely as I should be able to (and yes, the parking brake was off).

2. After turning the truck off when the brake pedal is stuck, once under the hood, I can hear a hissing sound coming from the master cylinder/booster. When the hissing is done, the pedal pops back up on its own.

Seeing as how I don't know any ABS specialists that I trust (I really don't want to go to the stealership), and I don't want to shell out $600+ on an ABS unit that I'm not sure is bad, is this too far from being reasonable? My booster or master cylinder is faulty which is causing the lock ups. The lock ups are causing the ABS unit to go WTF? and kick out codes. Another thing that leads me down this road, again, not sure how reasonable it is, is that the ABS light only turns on after the first time that the brake pedal won't return. Up until that point, it's fine.

Any help is appreciated. I'm seriously about to just go to my local Checker's and pick up both a booster and a master cylinder, they have them both in stock for less than $120 for both.

[ct9a]

Well, I went ahead and replaced both the booster and the master cylinder. This fixed the problem. Now my pedal returns perfectly and the brakes no longer stick. I still have ABS codes though, even after disconnecting the battery for a couple of minutes. I'm going to go pull the codes in a bit. Thanks everyone for the help.