Is my Master Cylinder Toast?

[Cable]

Hey guys, I picked up my '75 280z in late June 2009 as a non-runner. It has been sitting for the previous 3+ years. When going through my engine bay prior to my LSx swap in early July I removed the master cylinder to avoid getting paint on it. On Monday earlier this week I re-installed the master cylinder, installed Russell Speed Bleeders on all 4 corners, and added new fluid and began the bleeding process starting with the master cylinder itself, then the pass rear bleeder, driver rear bleeder, pass front bleeder, and finally driver front bleeder.

 

After getting all the air out of the system I am still having issues with getting the brakes to work. The pedal gives me some resistance vs when I first started bleeding the system, but still goes to the floor, even if I pump the pedal repeatedly with all the bleeders closed.

 

I have since re-bled the system 4 times since, including the master cylinder, and I even tried using a vacuum pump and gravity bleeding. No changes. I haven't driven the car yet but I have inspected the pads and shoes and they look great. The rear drums are adjusted correctly as well.

 

So this leaves me thinking that the master cylinder could be bad. I figure it might be bypassing internally since it doesn't leak a drop, thoughts on this?

 

Thanks guys!!

[jt1]

It's hard to say. Sometimes when a master is dry, it's a real PITA to get the air out. All the brake bleeding threads you see are a testament to that, and I've been thru it myself. I would make several attempts at bleeding it, and bleed the master first each time, before I gave up on it. A pressure bleeder works best. It's easy to fab one up if you have an old master cap. Just silicone or JB weld a fitting into the cap.

 

jt

[S30TRBO]

Have you tried to bench bleed the master first? If not since it is mounted already unhook the lines on the side and poor fluid in the reservoir and let it come out of the sides (gravity feed) getting all the air out then re-attach the lines up and bleed normally starting from farthest away from the master.

 

You can also take the lines off and have someone pump slowly while you put your finger over the hole to see if you are getting any suction on your finger. If not I would just buy a new master for gp sakes.

 

Good Luck keep us posted.

[Cable]

My master cylinder has bleeders on the unit itself. I have bled the master cylinder three times using those bleeders and some tubing looped back into the reservoir. No air bubbles have come out since the first time.

 

I know the master cylinder is pushing fluid because I do have fluid coming out of the bleeders on each corner, but it could still be bypassing internally.

 

I think I am going to buy another master cylinder, but I wanted to hear other opinions before I blow another $60 on a part that I may not need on a project that has already exceeded its budget.

 

Thanks for the replies guys.

[Cable]

The master cylinder was the problem as I suspected. Against my better judgment I replaced it with a reman unit after going to 3 different parts stores and ordering a new unit only to get a call a day later that they couldn't get a new unit afterall from their suppliers at the prices quoted. So I went ahead and bought a reman unit and crossed my fingers. If it fails it has a lifetime warranty, but if it does fail I will prob just bite the bullet for a brand new piece instead of having to swap out a master cylinder every so often, even if it does cost me $150+ for a brand new one.

 

Thanks guys!!

[datsun79z]

Progect BBZ;

 

Do a search on "Reaction Disc". I hope this helps you out. Keep us advised of your progress.

 

Mike

[Cable]

Progect BBZ;

 

Do a search on "Reaction Disc". I hope this helps you out. Keep us advised of your progress.

 

Mike

 

I've already read the 'sticky' on it, I doubt I have any issues with it, but won't know for sure until I actually drive the car...