Problem with Z brakes....

A quick summary of what parts were installed:

  • 30mm Z Calipers
  • 30mm X-drilled rotors
  • Front and rear SS lines to mate to the Z calipers

Alright, so it comes time for me to put everything on my s13, so I first take off the stock calipers and install the Z rotors and calipers. After that, I installed all the lines.

Then I bled the system quite thoroughly, in the order the FSM says. Double checked to see if all the lines were tightened, and began checking for leaks. There were none.

Bled the system again, knowing that because we’ve takin off all the lines, there must be a lot of air inside.

Here is the Problem:

Upon start up, when pushing the pedal down a few times, there was a very loud and noticable hissing sound coming from it.
It felt nice at first, but as soon as I started to drive it out of my shop, and applied the brakes, the pedal went straight to the floor. It wasnt grabbing at all.

Checked for leaks again, and there were none.

I talked to a caliper rebuilder who personally has a 300zx and he said that it could be the seals between the two halfs of the caliper that were either broken or not torqued properly.
I sent it out to him and had them rebuilt, and when we put everything back together again, same problem, only this time it made a little difference. Pedal was still going to the floor and not driveable.

If there is anything that I missed, or I should have done, can you let me know.
If you can help me out as to what the problem is, it would be greatly appreciated.

the hissing sound is coming from the booster or MC for sure.
I was just wondering, if that would mean that it is too weak to pressurize the system for the bigger brakes?

My booster works fine for me… check for a vaccum leak…

What method have you used to bleed the brakes, try vaccum bleeding it.

Are there any leaks anywhere in the system that you see brake fluid
comming out?

If there is still something wrong once the they are properly bled it could
either be the master or booster…

Ive bled it many many times. Somewhere around 10 times. I used the push, push, push, hold etc. method. Checked for leaks, there are none.

Its not leaking any fluid for sure. Everything was installed correctly as well.

I dont think the MC would make the hissing sound, so i guess it has to be the booster.

Iquabob, u didnt hear anything after you installed the brakes? anything along the lines of hissing?

its push, hold, push, hold…

if you push push push hold…alll you will get is air in the system…

for my car, i let it drip for about 30 min each side keeping the ms filled all the time

There is a section in the FSM (I think … or is it Haynes?) that describes how to test if your booster is working properly.

But if you can just put your pedal to the floor clearly you are having pressure loss somewhere … not sure if the test will help you figure out much.

sounds like you got a serious air pocket somewhere you gotta bleed those breaks better. i had to bleed mine for about 40 mins before it was fine. if the calipers were rebuilt and you got no leaks anywhere then it must be air pockets and if the old breaks worked before that mean the MC is fine.

the brakes were working fine before i put the Z brakes on yes, but there was a faint hissing sound as well coming from the booster/MC.

I didnt bother changing it, but i guess it has to be that.
Ive bled it many many many times, but ill keep trying that.

when bleeding dont just hit the pedal if there are air bubbles in the system youll be able to hear them travel through as you bleed the brakes i had one air bubble that took me like 30 mins to move from the front to the bleeder nipple on the rear caliper.

keep trying if nogo it maybe the MC but lets hope its the air bubbles

If your brakes were fine before, i doubt its the MC. When you installed yoru calipers did you align them so the bleeder screw is on the top or the bottom? They need to be on the top… this might be your problem.

I did align them so it is at the top.

Before i installed the Z brakes, there was a hissing noise as well but you could only hear it inside the car, but with the new brakes installed, its so loud you can hear it outside.

My bet it is the booster as opposed to the MC.