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

[gbrtng]

Originally Posted by | 1990 ZR-1 |

I'm really hoping that's the case. I bled the right rear then left rear, then right front and left front. I had my wife pump the brake pedal twice and hold it while I opened and closed the bleeders all while topping off the reservoir with new fluid.

Sounds like you got it right - the trick is to get the bleeder closed before wifey releases the pedal each and every time. BTW, the 90 ABS unit has no bleeder screws so if there is a bubble trapped there ??? what to do.

One other trick - I have the wife put her other big toe under the brake pedal so it does not go all the way to the floor. Somehow I feel better about not running the master cylinder plunger all the way to the end of its stroke.

[| 1990 ZR-1 |]

Originally Posted by Aurora40

Can you post a link? I don't recall having that problem. The biggie I had was installing Baer 6-pot calipers, the OEM banjo bolt was too long and was pressing the piston out. I couldn't get the car to *not* brake, they dragged really badly. Baer sent me a shorter bolt.

I did have a longer pedal after that. The DRM brake spring helped, but there's no getting around the larger piston displacement. They weren't scary, though.

Hmm, well one time they were scary at the dragstrip (braking from 115, they'd give out by around 80), but that was due to the sissy ceramic pads Baer included. A swap to Hawk's cured that.

It does sound like you have air in your lines, though. Also, supposedly it's not a good idea to press the pedal to bleed, as you can move the pedal through longer travel than it experiences normally, and can jack up seals. I dunno how true that is. I use a Mityvac to bleed brakes, and then gravity bleed to get any air that was sucked in around the bleed screw.

Here you go Bob. If you remember, I'd love to know how you fixed your problem sine mine sounds awfully similar to yours.

http://www.zr1.net/forum/showthread....ht=soft+brakes

[| 1990 ZR-1 |]

Originally Posted by BlackWidow#2

Did you bleed the ABS unit? You have air somewhere in the system I would bet.

How do I do that?

[| 1990 ZR-1 |]

Thanks for the feedback guys. I will try bleeding the brakes again this weekend. Hopefully that'sthe problem....
I went with a Valvoline DOT 3 & 4 Syntetic Brake Fluid. Any reason I should go with another brand?

[ittlfly]

Originally Posted by | 1990 ZR-1 |

How do I do that?

The short answer is, you don't . As I *recall* it used to take a dealer with a Tech 1 and / ABS cartridge used to cycle and purge the ABS unit. Maybe some one has come up with something else...

[mike100]

Originally Posted by | 1990 ZR-1 |

Thanks for the feedback guys. I will try bleeding the brakes again this weekend. Hopefully that'sthe problem....
I went with a Valvoline DOT 3 & 4 Syntetic Brake Fluid. Any reason I should go with another brand?

$6 parts store DOT3 until you get the kinks worked out. A good dot3 flush is cheap-you can bleed in some premium stuff right before you go to the track.

[gbrtng]

Originally Posted by ittlfly

The short answer is, you don't . As I *recall* it used to take a dealer with a Tech 1 and / ABS cartridge used to cycle and purge the ABS unit. Maybe some one has come up with something else...

I looked thru the 91 FSM section 5 and there is no special method for bleeding the ABS modulator when hydraulic lines are disconnected during repair. Later model C4s have bleeder(s) on the modulator (I think) but I don't know when the change was made.

The FSM bleed sequence is RF, RR, LR, LF - not the sequence I mentioned earlier.

However --- there is a caution note in section 5E1 to never charge the battery with a quick charger with the negative battery cable connected. Failure to disconnect the negative cable could result in the BRAKE fuse to blow or serious damage to other electrical components. YIKES !!! How many AAA bozos know that requirement? How many ECMs have had their service life reduced by a quick charge? And who would look in section 5E1 for how to connect a quick charger? BEWARE ...

[gbmidyear66]

Originally Posted by | 1990 ZR-1 |

I just finished a full brake overhaul with new rotors, new Hawk HPS Pads, braided stainless steel brake lines, and flushed the fluid with Synthetic fluid.

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

[Aurora40]

Originally Posted by | 1990 ZR-1 |

Here you go Bob. If you remember, I'd love to know how you fixed your problem sine mine sounds awfully similar to yours.

http://www.zr1.net/forum/showthread....ht=soft+brakes

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...

[Aurora40]

Also, you could probably cycle the fluid in the ABS module by hammering the brakes in the rain. I never did anything to specifically bleed it.