ABS Problems

**alfaparticle** · #1 (**permalink**) 11-01-2007, 06:08 PM

My ABS brakes have worked pretty well since I bought the car 2 years ago. This weekend I replaced the front calipers and the flex hoses because I had leaks and unpredictable pulling to one side. Now, the ABS light comes on as soon as I touch the brake pedal and the braking performance is poor. It seems like a bad accumulator. With the car stationary and the ignition on, when I push the brake pedal the ABS light comes on and the pedal sinks towards the floor, then at almost the end of the travel the light goes out and I feel a kick back in the pedal. The pump runs all the time that the ABS light is on.
Is it a pure coincidence that my accumulator crapped out at the exact time that I replaced the calipers or am I missing something.

Thanks,
Ed Prytherch
79 Spider
2 x 88 Verde's

AR4me · #2 (**permalink**) 11-01-2007, 06:15 PM

Happening at the same time as replacing calipers and flex lines is too much of a coincidence to me. Did your bleed the brakes properly?
Jes

**alfaparticle** · #3 (**permalink**) 11-01-2007, 06:35 PM

I bled them the same way that I have always bled standard brakes. I did it with the ignition turned off. I have a small glass jar with a hole in the lid. A plastic tube goes through the hole to the bottom of the jar. I attach the other end of the tube to the bleed nipple, open the nipple and pump the brakes until there are no air bubbles. I tighten the nipple with the pedal fully depressed. I did it twice on each side as I replaced the calipers on Sunday and the hoses tonight.

Ed

AR4me · #4 (**permalink**) 11-01-2007, 07:01 PM

Hmm. Yes, fronts are bled with ignition off (while rears require ignition on). Are you sure you got all air out? Do you get pedal pressure if you pump the brakes?

If tube is out of fluid in jar or nipple is too loose you can suck air back in.

Jes

**alfaparticle** · #5 (**permalink**) 11-01-2007, 07:15 PM

The pedal is firm with the ignition off. The jar had plenty of fluid over the end of the tube. I pumped it several times after the bubbles had ceased so I think that there is no air in the system. Could a little air in the system cause it to loose pressure like this? The pump runs everytime I push the pedal.

Thanks,
Ed

AR4me · #6 (**permalink**) 11-01-2007, 07:22 PM

With a healthy ABS system the pump should come on with every 5-6 application of the brakes. As the pump/acc gets old it will come on more frequently.

If you have no air in system and it comes on every time you press the brake pedal maybe it is time for the Buick ABS parts. Besides the pump coming on every time the pedal also goes sinks to the floor? Do you gain pedal pressure if you pump it?

Jes

JoeCab · #7 (**permalink**) 11-01-2007, 07:30 PM

Quote:

Originally Posted by AR4me

Hmm. Yes, fronts are bled with ignition off (while rears require ignition on).

**alfaparticle** · #8 (**permalink**) 11-01-2007, 07:32 PM

The ABS light stays on and the pump runs continuously if I pump the brake pedal. If I maintain pressure on the pedal it slowly sinks to the floor. The pump stops and the ABS light goes out when the pedal is at or near the end of its travel.

I have a spare pump and accumulator that is supposed to be good. It looks like I should swap it out, right?

Does it sound like just a bad accumulator or a bad pump?

Thanks,
Ed

**alfaparticle** · #9 (**permalink**) 11-01-2007, 07:37 PM

I remember now that the ABS light used to come on if I made a very hard stop. I also had occasional problems in the summer when it was very hot under the hood. I put a heat shield against the pump and I had no more heat related problems.
Ed

JoeCab · #10 (**permalink**) 11-01-2007, 07:38 PM

Quote:

Originally Posted by alfaparticle

Does it sound like just a bad accumulator or a bad pump?

slyalfa · #11 (**permalink**) 11-02-2007, 01:10 AM

If the pedel goes to the floor I think the master is bad, working pump or not, working accumulator or not.
the pedel should not sink. I have had to change the master once when that started to happen to me.
As far as I know no one has a seal set for it so you have to find a new/used one.
checking for air one last time will not hurt. Did you blead the back too? that one is easy just put a stick on the pedel so it is part way pushed.(I slide the seat forward to push the stick) and then go back and open each of the bleaders one at a time the pump will flow as much as is needed. keep the tank full. it is good to let it run a bunch to clean out the old.

P.S. the key needs to be on

sh0rtlife · #12 (**permalink**) 11-02-2007, 02:00 AM

stick a vacume bleeder on it and try again...pull a air bubble free bottles from each corner...now i paid hell bleeding my gtv6 and found that i had to teflon tape each bleeder to keep the system from sucking unwanted air back up into the lines....ive done the same thing on the last 3 cars ive done and it makes the bleed go that much faster and smoother

if the pedel is slowing droping the master is shot or has air in it...no 2 ways around it

NMMilano · #13 (**permalink**) 11-02-2007, 08:46 AM

What are the chances of any component failure with that kind of timing???
My experience with both the pumps and accumulators is that they fail over time not suddenly. Start the bleeding process over! From what you discribe you have air trapped in the system. One of the functions of the light is low pressure, so you start and the pump is running. Pressure builds, light goes out. (pump must be working) Now you depress brake pedal, light comes on. Air must be in the system, now getting compressed. Air is compressed, system comes up to pressure, light goes out and pedal kicks back. Some Milano abs systems need lots of priming, when the system is open put as much brake fluid in all the components as you can. Those one man bleeders are cheap and work great drawing fluid through the lines.
Good luck

**alfaparticle** · #14 (**permalink**) 11-02-2007, 08:58 AM

Would the pedal be hard with the ignition off if there was so much air in the system that it was causing this problem?
Ed

**alfaparticle** · #15 (**permalink**) 11-02-2007, 02:31 PM

I swapped out tyhe accumulator from the used spare pump. It had no effect but no liquid squirted out when I unscrewed it. There was zero pressure in the system. I don't know the history of the spare pump. Dave Robinson gave it to me when I bought the car from him about 3 years ago.

I bled the front brakes again. My wife pushed down on the pedal and I cracked the bleed nipple under pressure, then closed it again before she released the pedal. I got a small air bubble out of each caliper on the first stroke but no more. We pumped quite a lot of fluid through with no sign of air.

The pump ran for about 5 seconds when I turned on the ignition then stopped and the ABS light went out. But the pump ran as soon as I touched the brake pedal and kept on doing it, as before.

I drove the car and the brakes feel pretty good. I had no problem locking up the wheels at 30 mph and the pedal effort was ok. But the ABS light comes on whenever my foot is on the pedal.

I think that it is the accumulator. The spare was probably bad.

My other Verde is in Colorado and my son is driving it. It seems to have an accumulator problem too and I ordeed one from AC-direct a couple of weeks ago. But we still don't have it and they are dragging their feet about finding out where it is. It looks like it never made it to UPS. I am reluctant to order another one from them until the first one is resolved. I will look for an alternative source that is not too expensive.

Does anyone have other ideas?

Thanks,
Ed