I have been in the process of doing a lot of brake work and was working on replacing the brake booster and master cylinder today.  Once the old units were out of the car I was able to get a good look at the clutch master and I'm concerned.  First off, the reservoir is bone dry, then it looks a little rough around the master cylinder and lastly it looks like it may have been leaking on the inside of the car.  It is really hard to tell since the brake master cylinder seems to have been leaking based upon the condition of the under side of the booster and the inside of the firewall.  Pix of everything below.  What do you guys think?

 

 

I would replace...they are cheap.  Just a bit of work/contortion to get the pin out under the dash.

Inexpensive to replace, Easy to get to with the booster out and your already under the dash side by side with the pedals. With it being dry the slave cylinder could be leaking as well. Pull back the dust cover and take a look.

Edited November 8, 20204 yr by Yarb
Update

I have just read that when replacing the clutch master it is recommended to also replace the clutch slave.  I see two different clutch slaves available.  I am guessing you match up the slave to the year tranny you have rather than the chassis right?

@motorman7 and @Yarb, that is kinda what I was thinking...especially since it looks be be much easier than the brake work I'm already doing.  🙂 

The newer self adjusting one works on all Zs. 

This is what I am using.

https://zcardepot.com/products/clutch-slave-cylinder-240z-260z-280z-72-78?_pos=5&_sid=7db12e4c4&_ss=r

1 hour ago, texasz said:

 I am guessing you match up the slave to the year tranny you have rather than the chassis right?

I think it matches your clutch fork.  The adjustable ones have a hole in the fork, and an adjustable rod in the slave.

The newer slave works with the early fork. Just swap over the shaft. 
 

I'm guessing that your brake booster is shot?  Once brake fluid gets in there, it messes up the diaphragm.  I just had to replace mine due to a leaky master cylinder. 

I had done the clutch master and slave years ago.  I seem to remember needing to transfer over the original push rod on the clutch master to the new one, because the new master had a shorter rod.  The shorter rod wasn't long enough even with the pedal connection spun all the way to the end.  It just didn't have enough throw to completely disengage the clutch.  

http://www.pwrbrake.com These guys can rebuild your booster for you.

Here's where I landed on the brake stuff...I got the Wilwood 1" master and an 8.5" booster with a conversion mounting kit to prevent modifying the firewall.  Here's a link to the booster for anyone interested:  https://jdm-car-parts.com/products/datsun-240z-8-5-inch-brake-booster-upgrade-kit-for-1969-1972?variant=2376693317641

 

I'm keeping all the original parts in case I want to revert back to stock at some point so thank you for the tip on who can rebuild the booster.

 

Here's a picture of the brake items ready to be installed after I address the clutch master cylinder.