OK, I'll try to keep this short. I've been having brake problems on my Z for a long time. What I get is the car feels like I'm pumping the pedal when I'm not. The car lunges foward a little then back as if i'm varying the pressure on the pedal. The pedal doesn't pulsate. It doesn't do this everytime I brake, just most of the time. This started on the original rotors & pads. They were replaced w/ slotted & drilled rotors & new semi-metallic pads. The problem continued but wasn't as noticable w/ the new hardware on. As that set wore, the problem got worse. I thought the rotors were warped, again as is the general opinion here. Just put on new rotors & pads, same thing. The problems is still there, just not as noticable. Tire are new & balanced.

What is the problem????? Could it be a problem w/ the calipers?? Do the lines have to bled??? Master cylinder??? Rear brakes???

I have checked the ABS system by pulling the fuses.

Please help?!?!?!?!

 

ttt Anyone?

 

Did this start after any particular thing happened or changed??
Does it only do it while you're braking?

 

It only happens under braking. Just driving, there is no shimmy or anything but smooth.

 

ttt

 

check if theres crap in the lines, it could prevent the fluid from returning as fast as you would expect

 

You said you checked the ABS? did you deactivate it and drive it? Because it's irregular I would point towards an electrical/ABS problem. Maybe a wheel sensor is bad or is flickering from good to bad. If it was a broken line your brakes would not stop as well, not put more pressure on the system/brakes. So your problem is that something in the brakes is creating a higher pressure than the pedal is creating. ABS is really the only thing that would do this.

Ryan

 

forgot, not all ABS problems will throw a ABS light, just persistent ones. Also, pulling the ABS fuse is not the only test to rule it out. Try and get it scanned while driving....see what those wheel sensors are doing, and if the ABS is activating when it should be.

Ryan

 

I'm not getting any ABS lights. I did pull all the ABS fuses & drive it, no difference. The pulsing of the brakes I get is slower than what ABS would do. One thing I tried today was to grease the caliper pins. The bottom 2 were alost dry & it took a lot of effort to remove them. After greasing, I put it all back together again & braking improved, but the pulsing presisted, although less than before. I'm going to bleed the lines next. Other than replacing the calipers, it's the only other problem I can think of.

 

i would rebled the lines and make sure no crap is in the lines. also check if the calipers are moving corectly

 

You might want to check the caliper pins (the metal sleeves they slide on) to make sure they are well greased. If they get dry they can seize, and may not apply direct pressure (could also make it drag the pad against the rotor, possibly causing warpage)

 

Update: I've replace the rear rotor & pads over the weekend. The problem appears to be gone. The rotors were well worn. The pads were extremely thin. The piston side pad was maybe 1/16". Greased the caliper pins. When I removed the calipers, the pistons looked to be almost fully extended. Once the replacement was complete, the brake fluid reservoir overflowed. But the pulsing problem disappeared. Hopefully, it will not return.

<- Happy Braker.

 

What is commonly referred to as "warped rotors" aren't in fact warped rotors at all. What you had is the most common type of "warp" cause. The rotor, for whatever reason, has varying coefficients of friction circumferentially. This is caused by uneven pad deposits. The pads themselves can also cause it if they're not completely square to the rotor, or if their surface is a little uneven. Bottom line, you needed a brake job and it fixed the problem.