Hi all,
I'm having a severe problem with the braking system on an 01 auto. It's got a little age on it to the tune of 105K with no real upkeep. The guy just drives the car, you know what I mean. I refreshed the car with new rotors, pads, Goodridge lines, Fluid and a master cylinder. I posted a couple weeks ago asking about Blue Racing Brake Fluid and found that not to be a problem.
Since putting all the new parts in, the peddle on the car goes straight to the floor. I know, you're thinking bleeding right here. Let me asure you that it has been bled and bled and bled with absolutely no improvement. The master was bench bled before the install. Even before the master went in, and I had everything else in, there was no peddle even after bleeding the lines. You can pump the peddle several times and build a little pressure, but once you stop it goes right to the floor.
So, I went to the local Stealership to ask some advice from thier brake guru. I was given suggestions to check such as a sticking slider and so on. No check resulted in anything wrong. His one suggestion was to pinch each brake line at each corner at the same time and see what peddle travel I had. So, I put the old lines back on, bled them and pinched them. He stated that if the peddle went to the floor, there was a definate problem still in the caliper area. He stated if the peddle was firm (Which it was) that the ABS unit needed to be bled. He stated that the car has a self bleeding process for the ABS unit that is activated by an Autotap II. Have you ever heard of this?
If anyone has any suggestions, please throw them out there.
TIA,
Will

 

The ABS unit MUST be bled electronically if air gets into it. This is normally done with a Tech II scan tool. Not sure if any aftermarket tools do it.

The bleed procedure typically takes two people, one to run the procedure and pump the pedal about 1000 times, or so it seems, and the other to bleed the calipers and keep filling the reservoir. Better have about 2 quarts of brake fluid on hand - seriously.

During the procedure the ABS unit will cycle the various valves, run the pump, and make all sorts of weird noises.

If you replace the master cylinder, you should bench bleed it first to minimize the amount of air pumped through the ABS system.

Been there done it many many times.

 

Man, thank you for the response. I'm glad someone knows what that was about. I'll have to get on that now.
Thank you again.
Will

 

Have a 2nd person pump the brake peddle 3 or 4 times and hold the peddle down as you open the bleed screw and allow the fluid to drain.

Do this for each caliper. Rember to keep the cap on the MC or the fluid will fly all over the place.

 

Thanks, but it's not that type of bleeding needed. And I don't have an Autotap II to activate the ABS bleed.

 

(this means I am waiting to hear the outcome of this problem)

VR

 

Actully with pressure put on to the system and someone pushing the brake peddle down when you open the bleed screw that will open the should ABS and allow the fluid to move though. We do it this way all the time at the track. and have no problems.

or use the Motive Powerbleeder with 10-12 psi of pressure to push the fluid though the lines.

Other things to look at:

vacum leak
pad taper
bent caliper brakets
uneven pistons

combination of the above.

 

[QUOTE=AU N EGL]Actully with pressure put on to the system and someone pushing the brake peddle down when you open the bleed screw that will open the should ABS and allow the fluid to move though. QUOTE]

That's how I bleed the system usually with no problems ever like this. Got the Autotap II and engaged the ABS Bleed and guess what, no problems now. This was a true learning experience.

 

I am not sure this applies to our Vettes, but it could be the reason for the trouble you are having.

My neighbor is a mechanic. Six years back, when he heard my wife's Grand Prix-GT had ABS, he said to me......when it comes time to bleed those brakes with ABS, you'll have to use a vacuum pump at the caliper bleeder and suck the fluid out. Positive pressure (like pumping the pedal) will not work.

With that warning embedded in my mind, I've bled my wife's GP brakes recently using my $30 hand vaccum pump from NAPA with no issues.

Maybe that is why you are having trouble.

 

Glad it all worked out for you.

With all the brake work we do at the track with differnt guys cars we have no problems with the Motive Power bleeder what so ever, nor pumpping the brake peddle a few times.

 

I use the bleeder all the time, got it on ebay for 40.00 bucks a few years back and it works great.

Just used it to bleeds my C6 ZO6 Brakes on my C5

 

Pumping the pedal woorks fine for track use if you don't have exsisting air in the system (other than by/in the caliper) If you get air in the abs pump you have to bleed it electronicly. Their are valves,pistons, accumlators ect that can get air in them and if it doesen't get pused out it stayes trapped. It just stayes it the high spot. Glad you figured it out, this forum is awsome. ATI

 

Yep, the forum is great. I don't know yet how the air got in there as there was nothing strange done, but I suppose it did. I never knew about the a-tap II doing that either. This has been frustrating to say the least. Glad it's over, got a headache from thinking about this thing.
I appreciate all the advice given.