I'm in the process of replacing my clutch master cylinder. Old one was leaking at the firewall. I went with an O'Reilly's as they are the closest and had one in stock. During bench bleeding (connected a hose to the outlet and submerged back into the MC reservoir), was getting all the air out and then suddenly would get massive amounts of air in the bleed line when I pushed the piston all the way in. No matter how much or how many times I compressed, would still get a ton of air at the very end of the piston compression.

Thought I might have a bad MC so went and got another one from O'Reillys and same thing - tons of air getting in the line at very end of compressing the piston. Tried installing and hooking up to the firewall and connecting the hard line and bleeding from the slave cylinder and same thing - no pressure in the pedal and tons of air coming off the slave bleed valve. Took the O'Reilly's MC apart and rubber looked good, walls of cylinder were smooth, etc. so no noticeable damage or tears.

I genuinely try and stay away from anything O'Reilly's especially when it comes to my older cars but considering the same thing happened to both MC's wondering if I did something wrong? was a I pushing the piston too far in and getting air that way? Oddly enough, I took apart the old one, cleaned it put it back on and no longer getting leaks at firewall.

I don't want to rely on the old MC that has already been leaking and I'm not finding rebuilt kits anywhere for the MC. Could use some help on 1.). Am I doing something wrong during the bench bleed process and 2.) does anyone have recommendations on where I can buy a solid brand clutch MC.

Any and all help greatly appreciated.

 

Sounds like they were both bad to me. I just replaced both the master and the slave this last Fall. I ordered them from NAPA. Their stuff has been good for me. However, once I bought an alternator for something a while back and the store owner said as I left " keep your receipt"! My part was fine, but he had had a history of bad alternators and starters.

 

Thanks @spurredon . I ordered one from Napa this morning. I usually will pay the extra money and go the Napa route - O’Reillys was the only option on a Sunday.

luckily they are easy to swap out. Let’s hope I get one built on a Wednesday.

B

 

White Post Restorations in Vermont rebuilds them by boring out the cylinders and sleeving them with stainless steel. They could also be able to help with the bleeding technique.

 

When replacing both, the method of attaching clear tubing to the bleeder on the slave and running it into a partially filled container of brake fluid while pumping the pedal until the air is all forced out of both the master and slave, worked great for me.