Specter328

iTrader: (2)

Hi,

I've had a brake issue over the last few months and have changed quite a few parts including the booster, front calipers, soft lines to the calipers, and the master cylinder. The issue is a soft pedal or lack of torque when braking. I need my brakes for the track and my next step would be to switch out the ABS pump or delete the ABS all together. So, I need input from you track guys, what should I do? Keep ABS or delete it?

Thanks

gracer7-rx7

iTrader: (16)

fyi - 2MCHPWR had some ABS issues and has a few threads on troubleshooting. Might want to read some of his threads on the topic.

Specter328

iTrader: (2)

Thanks I will. I am unsure if it is the ABS but its one of the last points in my brake system that may be the issue plus it would be another failure point to take out of the system. Any thoughts regarding keeping ABS or removing it?

Fritz Flynn

iTrader: (263)

If you can keep it in place I'd highly recommend it. Braking is the hardest part of road racing especially when your car goes 150 plus mph and I can't think of a better advantage than having a healthy ABS system.

Gene

iTrader: (1)

Is this on an FD? The FD system is pretty good, you should keep if if you can. If your pedal is soft you might not be getting all of the air out, especially if you didn't bench bleed the new master properly. Or does the pedal get soft? That could point to a cooling problem or a bad choice in brake fluid.

Black91n/a

Soft pedal on track points to fluid fade and lack of torque when braking on track points to pad fade. Sounds like you'd be better off getting some higher temperature brake fluid and brake pads and/or getting some brake ducting.

Specter328

iTrader: (2)

The pedal is soft all the time all the time, on track, off track, hot brakes, cold brakes, not matter what. The MC was properly bled. How about the proportioning valve? Could that be bad?

finger lock

iTrader: (6)

I have a track FD that I run in SCCA ITE. It has the ABS removed and I haven't had any breaking issues that aren't pilot related errors.
I know another local FD racer who has kept his ABS but relocated it to the passenger footbox area to avoid the high temperature zone near the turbos.

gkmccready

Soft pedal means something in the system is compressing. Typically it's air somewhere, potentially it's a flex line going bad or something leaking (could be a pin ***** leak). Do a complete brake flush and pay close attention when you bleed the calipers for *any* bubbles -- use a clear tube so you can see them. Unless the prop valve or MC is leaking they shouldn't be causing you a soft pedal.

When's the last time you bled the brakes? And did a full flush? What fluid?

Specter328

iTrader: (2)

My brakes have been so many times since this issue has come about in August that I have lost count. Could there be air trapped in the ABS unit that I have yet to get out or see any trace of? That is the last thing I would have to replace because I'm at a loss which is why I'm leaning toward the delete.

Brent Dalton

iTrader: (31)

I'd keep it as well. The point that Fritz was making above was just driven home by Finger Lock when he said the only issue they have had with ABS removal has been driver error... which is why when slowing from 150mph-50mph, ABS is a nice little something extra to have in your hip pocket just in case . I have followed your numerous threads and know you have went through almost everything in your entire system. I know it has to be extremely frustrating. I do have a question, had you done any brake work when this issue first showed up? Can you tell us when and how it started? ie on the track or "just got in my car to drive one day and the pedal was spongy" etc, etc...

gkmccready

Could be. My TII doesn't have ABS, but I had a friend with it and recall the bleed procedure for the ABS unit was unexpected. C5 and C6 Corvettes need to use a TechII to cycle the ABS valves to get a full bleed done. You might try using a Motive Pressure Bleeder to see if that's enough to force fluid through the valves. My shop manual is at the, well, shop, so I can't dig through it for you... sorry.

Edit:

Guys without the TechII for their Corvette have reported success with putting the car on jackstands or on a lift and cycling the ABS. Doing a bleed. And repeating. Doing it in the air really lets you cycle the valves whereas trying to do it on the street can be problematic.

Specter328

iTrader: (2)

I would like to keep it but I'm really getting to the end of my patience, braking just before brake markers even start is getting old. It started while braking into turn 1 at Lime Rock in August, it almost felt like something let go on me as I had never experienced it before.

Specter328

iTrader: (2)

I'm going to have to try that thanks.

Brent Dalton

iTrader: (31)

Are you loosing any fluid?

gkmccready

From the day I bought my TII I had an issue with the RF caliper locking before anything else, caused me no end of trouble since I couldn't really get in to the brakes. This did, in fact, turn out to be the stock proportioning valve... but the peddle was always fine. Swapped the valve and things were better. Went dual masters later and haven't looked back. I would have thought a lot harder about that if I had to remove ABS, though...

Specter328

iTrader: (2)

Nope not a drop. I could find no leaks either, not even a small one.

Brent Dalton

iTrader: (31)

What kind of replacement parts did you use? new? used?

Specter328

iTrader: (2)

The booster was a low mile used one as were the front calipers, the lines were new, and the master cylinder was a "new" rebuilt one I got from NAPA.

Mahjik

iTrader: (1)

I would try a different *new* MC before anything else (unless you already have).

Fritz Flynn

iTrader: (263)

That's my vote as well

Specter328

iTrader: (2)

The old MC was replaced with the remanufactured 929 MC after the problem had begun. It was not rebuilt, I should have said remanufactured.

gkmccready

Booster shouldn't play a role in the pedal feel when the car is off, right?

Specter328

iTrader: (2)

Nope, this is only when the car is running. When the car is off the booster does nothing.

hwnd

iTrader: (4)

Replace it with a '99 spec ABS?