New Brakes....No Stopping Power....help please

[tomtom72]

Just a fwiw on the early ABS modules w/out a bleeder if you work on the system and then bleed, no air went into the ABS nodule. If you didn't get all the air out, and then activated the ABS system then you could get air in the ABS module, maybe. Depends where the trapped air is in the system.

The Tech1A + the ABS software will cycle the ABS, and using a pressure bleeder you can bleed the entire system at one sitting.

Or, you can get the air out manually, take a test ride and stomp the brakes to activate the ABS a few times and then redo the bleed. I do believe that when the ABS does a self test it only cycles the valves using the solenoids and no fluid is moved thru the system so if you had any air left from manual bleeding it would not necessarily get into the ABS module. This is how Jeff explained it in one of his posts if I remember right.

another fwiw, if you work alone the speed bleeders are worth the trouble to install. The one caveat is that you can not ignore the sealant on the threads, as it will wear out with use & leak air. I did minor work on my brakes and it took forever for me to get the air out working alone. The speed bleeders helped but still it took a few sessions to get it right. My next thought would be to use my Phoenix gun to do a reverse bleed as it would proly be quicker & more effective as far as working alone would be concerned.

I just figured to toss this out for your consideration as I found this system to be more troublesome to work on than my 72's brakes with respect to bleeding manually. I think it's the extra length to the brake lines due to the ABS plumbing.


Tom

[| 1990 ZR-1 |]

Originally Posted by gbmidyear66

I am just getting ready to do the same upgrade (Hawks, slotted rotors, braided lines....) to improve the mediocre braking on my 90. I hope your issue is as simple as residual air in the system.

Please post root cause (and your impressions on the new pads, etc) when you have it all resolved

Glenn

Will do Glenn. The Pads seem to get better and better as I put more miles on them. I really feel that i still have air trapped in and am hoping to get it all resolved this week end with another bleed session. I'll keep everyone posted.

[| 1990 ZR-1 |]

Originally Posted by Aurora40

Ah, thanks for the reminder! I must have blocked that out... I bled the calipers again, a few times actually. I believe that the brakes were as good as it gets at that point. Sometimes it would still have a long initial pedal, then the second application would be more normal. I believe that was due to the knockback of the pads, and the extra fluid volume it takes to move them vs the stockers (due to the increase in piston area).

Possibly some re-shimming of the calipers to get them more perfectly centered would have helped that, I dunno.

However, on your car, there is no reason it shouldn't feel as good or better than before you messed with it. Air in the line sounds like the most likely culprit.

Also, can you explain your bleed procedure in more detail? Did you open the bleed screw, have your wife pump the pedal twice, then close it? That's sort of how it reads.

Also, FYI, if you went to braided lines, watch the rear line. They don't have an angled exit from the caliper, and thus sit a lot closer to the edge of the rear wheel. Mine would tap-tap-tap on the wheel weight, until I loosely zip-tied it out of the way.

I have to say, on the brakes, I wish I had just stopped after putting on HPS pads. That was more than good enough, and completely headache-free. I am trying to remember that lesson on the V, and resist the urge to upgrade to the 15" 6-pots from the new one...

Bob, I would have her pump 2-3 times and hold the pedal in, than i would unscrew the bleeder to let the fluid out, and than would screw the bleeder back in not to let air back into the system, only then she would release the pedal and would pump again.

[Aurora40]

Originally Posted by | 1990 ZR-1 |

Bob, I would have her pump 2-3 times and hold the pedal in, than i would unscrew the bleeder to let the fluid out, and than would screw the bleeder back in not to let air back into the system, only then she would release the pedal and would pump again.

You definitely have air in there, then. You can not release the pedal while the bleeder is open, or it will suck tons of air back in.

You need to open the bleeder, press the pedal down and hold it, tighten the bleeder, then release the pedal. Repeat until air stops coming out (And watch the reservoir doesn't run out).

[Scrrem]

I am not a big fan of the two person method, but have used in the past. I just got done removing all four calipers to clean them up and hit them with some caliper paint (I know...cheap a$$). When re-installing I used a hand vacum pump at the bleeder screws and it took about half a resevoir of fluid before I felt comfortable that all the air was out. I drove the car last Sunday and the brakes felt great.
Rich

[batchman]

I've been fighting this same issue for a couple seasons. Have run probably a gallon of fluid through and had best result with the bleed order in the FSM.

Fresh hubs help as they always have play and as mentioned pad knockback is a contributor.

I think I'm going to try a Camaro master cylinder to get the 1" piston. But I misplaced the drawing I did for making an adapter... Gotta go through it again. These brakes are killing me on the track, never thought I'd get out of a Mustang and miss the brakes. Same caliper too!

Best,
- Jeff

[| 1990 ZR-1 |]

The brakes are a secondary priorety now. If the plenum pull goes well this weekend, I'll bleed the breaks again per FSM instructions and will post the results.

[Rex Ruby]

Originally Posted by | 1990 ZR-1 |

Dark brown gunk came out with little rust pieces especailly out of the front calipers.

I'd take apart the front calipers to inspect the inside condition then rebuild or replace as indicated.

Originally Posted by tomtom72

Or, you can get the air out manually, take a test ride and stomp the brakes to activate the ABS a few times and then redo the bleed.

I was going to suggest this. Find an area that has some gravel and hit the brakes hard to activate the ABS.

I had a soft pedal after some brake work, activated the ABS, rebleed, was 100% better then.

[| 1990 ZR-1 |]

Quick update. I had a chance to bleed the brakes over the weekend, and I definitely saw air bubbles come out. The brakes feel much better now, I also belive the brakes are still not broken in all the way since I have both new pads and rotors. The pedal feel gets better each day as I put more miles on them. Hoping in another couple of hundred miles they will be perfect.

[POWERBRAKEBOB]

The booster has one steel rod pushing against another, It can't collapse inside. You said new rotors, not remachined? Coarse cut on a remachined rotor will not stop. the surface looks like a phonograph record, and only rubs on the high spots. No good. Also check for any interference between the pad and the caliper piston boot. ANYTHING jacking the piston away from the pad will push the piston in. Loose wheel bearing will cause th erotor to sit at an angle pushing in th epistons. Oher than that, open the bleeders one at a time and let it gravity bleed, with the caps OFF.
We also build a ZR-1 style DUAL Diaphragm booster to fit non ZR-1 vettes. The stopping power is incredible.