Good Brake puzzle

[Reddog929]

1970 240Z Front brakes are good no air in the system (toyota 4piston). Back: Nissan Maxima disk. Had to rebuild driver side rear due to leak. Went to bleed get no pressure to both rear calipers and not much flow. When cracking the rear bleeder, the brake pedel does not go to the floor it stays the same. When Bleeding the front it does go to the floor.

Got some people helping me out and this is what we think might be going on.

1. porportioning valve locked out the rear when it was leeking. I have opened the electrical part on the top to get a look at the valve. Not sure what way it should be, at this point the small diameter part is at the firewall and the larger is just in view at the front.

2. Front part of the master cyl not working (1980 280zx master) on the 280zx it is opposite the original 1970 master cyl. So the front feeds the rear brakes.

Tryed to bleed the front to push the valve back in place. Did't work. Could have hydralic lock working against the rear keeping the fluid locked out of the rear.

I don't have the diagram of the distribution valve to see how the lock out part works. All my books in storage.

At this point I only have front brakes. Anybody run into this before? Need some help/suggestions.

[ZCurves]

Check to see if the Piston is free in the rear caliper. You could also remove the bleeder screw and see if the fluid passage is not plugged up.

If the piston is bound up, remove the Hard Line and blow it out with compressed air - be careful it will really pop when it shoots out.

If this is not the case, I am leaning toward the front portion of of the master cylinder malfunctioning. You can test this by pumping the pedal with the Hard Line off the rear caliper and see if fluid is getting back there.

Side note: It is always a good practice to rebuild BOTH calipers, rather than just one. This way you are ensured that your getting even pressure applied to both wheels.

[BTF/PTM]

So you have the 280zx master cylinder pistons feeding the warning light block backwards? I have a 280zx MC, too, but the lines are criss-crossed so the piston marked "F" still feeds the front of the warning light block. Are the pistons inside the MC the same such that you can just reverse the lines like that?

[jmortensen]

Are the pistons inside the MC the same such that you can just reverse the lines like that?

Yes..

[Reddog929]

I have them reversed.

[Reddog929]

I will give that a try. I rebuilt all four calipers last summer at the same time. This one thought I did not do a good job and decided to leak. I will let you know how the MC goes.

Thanks

[Reddog929]

Its been a long day sorry I have the lines at the warning block going to the correct MC locations.