ABS pump failure?

Jerm83 · #1 08-10-2006, 01:10 AM

I have a 99 silverado and lately the brakes have felt soft. my foot sinks easily when i hit the petal. The pads have pleanty of meat on them so is it the ABS pump? If not, what else could it be? Air in the brake lines out of no where?

Sonny01 · #2 08-10-2006, 06:41 AM

The pump only activates if a wheel is slipping and you can feel it and hear it...you have another real problem and it sounds like air in the lines. Has anybody worked on your brakes recently? It's a closed system and air can't get in...do you have a service light on? You might have lost either front or back brakes through your master cylinder...I wouldn't drive it until it's figured out. Do you have a full brake fluid reservoir? I think on these trucks if you lose 1/2 of your stopping capability through your master cylinder the parking brake light comes on .

Jerm83 · #3 08-10-2006, 06:42 PM

No i have not had any work done on the brakes. The reservoirs are full. Ok so i know that its not a good thing but i bought the truck last year with the abs light and the brake light on. I had a fix it tag from the dealership but i couldnt get it to them before they said it expired. The only reason i didnt get it checked was because i didnt have the money and i couldnt feel any problems in the brakes or divability. It drove like new and i have just kept putting it off because of my hectic work schedule. Now that the brakes have gotten worse, i and concerned. I know it wasnt a good idea to wait so long but i cant go back, so here i am. Would the computer tell that the master cyl has failed if hooked up to a reader? Also, i have had a master cyl go out in a truck before and it doesnt feel the same. It was a 1972 truck but it had front power disc brakes.

guumbah · #4 08-10-2006, 08:58 PM

After the pedal sinks to the floor, does resistance come back if you pump it? Also, I believe if the lights are on it should show a code if you hook up a reader.

Jerm83 · #5 08-10-2006, 10:49 PM

Quote:

Originally Posted by guumbah

After the pedal sinks to the floor, does resistance come back if you pump it? Also, I believe if the lights are on it should show a code if you hook up a reader.

Yes it builds up some resistance but not as much as it should. I drove it tonight and i think i figured out what is going on. It feels as if the front brakes barley work and i am actually using the rear to stop. When i brake, it feels like the rear end is dragging (like there is no resistance up front and the rear end is almost dragging me to a stop. Its not a dangerous ride, you just got to keep your distance on people. If that is the case, does that mean that the master cyl. is gone?

Thanks for the help

guumbah · #6 08-10-2006, 11:34 PM

Could be master cylinder. Could be one or both of the front pistons. These trucks don't have brake balance controllers in the ABS, do they? If they do, it could be that, but I don't think they have them.

Jerm83 · #7 08-11-2006, 12:44 AM

Any idea on how i can start to narrow down the problem? Whats the best way to check if your master cyl is good or not?

Capt. Delta · #8 08-13-2006, 12:51 AM

Re: Mushy brakes. I'm only mentioning this too you as an outside possiblity. My 99 Silverado did exactly the same thing in Oct. 05. Dealership said the fluid had been contaminated and all the seals were swollen. They said it is not an uncommon occurance with fast oil change places. Kid goes from flipping burgers at Mickey Dee's to working in an express lube. Grabs the wrong bottle and puts it in the brake fluid reservoir. Mine cost $3000 to replace the whole system and its still not right as "Sonny" well knows. He was a big help figuring out my problems. Anyway I hope that is not your problem. Just thought I'd mention it as something to keep in mind.

Jerm83 · #9 08-13-2006, 07:40 PM

Thanks for hte replys. After trying to troubbleshoot the problem more here is what i found. When i pump the brakes it only builds a little bit of pressure. Kind of like just the fluid in the lines building up pressure not the master cyl. But it does not build up pressure enough to make the pedal hard. Would that be the master cyl going out? Also, i have not had the brakes bled since i bought it last year. The brake fluid looks a little dirty in the resavour. Could old fluid cause this?

Thanks

Sonny01 · #10 08-13-2006, 07:50 PM

I forget the term for it but brake fluid attracts and retains moisture. Your fluid should not be dirty since it's a closed system. You need to have your system drained, filled and bled. Keep us posted.

Jerm83 · #11 08-15-2006, 06:10 PM

Quote:

Originally Posted by Sonny01

I forget the term for it but brake fluid attracts and retains moisture. Your fluid should not be dirty since it's a closed system. You need to have your system drained, filled and bled. Keep us posted.

will do, thanks for the help. I cant get them bled until next week so i will update you guys then.

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