240z series 1 master cylinder

[Kenmataya]

I've got a 70 June production car.  MC was leaking - Trying to keep it OG, so I found a pricy rebuild kit for it.  Pulled it, cleaned it, took out the retainer bolts.  The back cylinder slid right out, but the front cylinder is hitting on something and won't come out.  i've got it completely apart except for the big plugs where the brake lines connect.  I'm trying to get them off to confirm that they're not locking up the front cylinder.  big 29mm bolt head.  I cannot get these things loose - any suggestions? Or any other idea why the front cylinder is locked up??

 

 

Thanks,

Ken

[datzenmike]

Looks like you have the stopper pin out so it should come out. The two large 'plugs' hold the residua valves so make sure you don't get them mixed up. One is for the front disc and one for drums. These won't be holding the rear piston in. (the rear is in the front) Use the vice to hold the plugs and turn the master to loosen them.

 

I would get a block of wood and strike the master cylinder downwards onto it to dislodge the 'stuck' piston.

[Kenmataya]

well, its catching on something, i can press it down and release it and it "clicks" against something solid - its not just sticking in the bore.

 

and regarding the plugs, i've gotten a 2 ft breaker bar on them and they're still not coming off....

Edited March 23, 2019 by Kenmataya

[datzenmike]

 

I didn't know there were two stopper pins.

 

On the engine side probably between the two reservoirs, on the side is another stopper pin. Have a look...

[Kenmataya]

yea, there's one for the back cylinder and one for the front, both are out.....

[datzenmike]

Out of ideas. Did you hit it downward on a piece of wood?

[Kenmataya]

yup, lots.....  need to get those caps off.  unf, my cheap ass harbor freight vise broke.....

[grannyknot]

Any progress?  You probably want to remove those 29 mm plugs so you can get them re plated but there is a lot of surface area on those thread and the cast aluminum will be corroded around them, the aluminum might crack before letting go.

Because of the age and wear on your MC you might find that the bore walls are too far gone to be able to get a good seal with the new rebuild kit.  You could drill a hole in the front end of the MC and push the cylinder out then have the hole plug welded back up.

[Kenmataya]

Hello,

 

i was able to break loose the 29mm plugs, no damage.  And yes, my thought was drill a hole and then plug it, but I just can't figure out what its locked up on...... there should be nothing.

[grannyknot]

Could be just the lip of the seal catching on some crud that built up in between the pistons,  almost certainly you are the first one to open the MC since it was new, so 49 yrs.

You got the plugs off, I'm impressed.  I hauled on mine until I thought it would break then just gave up.

[Kenmataya]

yea, it was not easy!  Don't think its a seal catching - its a solid "clunk" when i compress and let go the cylinder. going to take it to my local machine shop, see what they can do.

 

Thanks for your help!

[grannyknot]

I have an old one in the metal scrap pile, I'll have a look at it tomorrow but I can't think what that would be stopping it.  If you can push the cylinder down toward the front, try giving it a shake while compressed to see if anything is rattlling.  You could also try popping it out with compressed air shot into the hole at the bottom of the front reservoir.

[yenpit]

Have you tried blowing it out with compressed air?  If not, and you want to try it, make damn sure it's not aiming at a car or glass window!!  KAPOW!!!  They will fly out hard!!

 

If the original seals are hard & brittle, they might get hung up on a dirty ridge & they might go "clunk".....??

 

TJ