The Cessna 120-140 Association Forum

Where can I find a rebuild kit break master cylinder for 2946 cessna 140

Hey labo,
I am not sure that there is a rebuild kit. If you still have the original master cylinder, the master cylinder is overall pretty simple. With the help of an A&P, it might be worth disconnecting the master from the pedal and unscrewing the top of the master cylinder (keeping the reservoir in the airplane). That way you can take a look at what needs to be fixed and order parts as needed. By taking off just the top of the master, you don't lose much hydraulic fluid and the parts should come out connected to the top.

Me and my A&P recently did this on my 1946 140 and replaced the O-ring (PN: AN6227B-7 - this seems to have replaced AN6227-7) due to a non-functional left brake. I would think the only "wear items" would be the o-ring and the spring.

Below are images from the parts catalog.

This is the way to go. If you find you can't extract the spring, a paint can opener filed to a little narrower than the spring opening will fish it out. Removing the body is easy, re-installing not-so-much, and generally just need to work from the top. I found that the bends in the right brake trajectory to the caliper trapped air to the point that only vacuum bleeding from below worked - pressure did not for some reason...