Rebuilding Your Brake
By: Arky Foulk
THE SYMPTOMS OF
LEAKING BRAKE MASTER CYLINDERS ON BONANZAS
1. Parking brake
will not hold.
2. Brake fluid on
belly of the airplane or puddles fluid under floorboards.
3. Fluid puddles
on top of Master Cylinders.
I have been able
to rebuild almost all master cylinders without removing the master
cylinder from the
airplane using the following procedure:
the airplane has the late-style parking brake valve mounted beneath the
floorboards, it will be necessary to drain the brake fluid tank. Unsnap and
remove the front carpet and carpet pad. (Do not remove the
a rag or shop towel and pack around the rudder pedal to prevent dropping
tools or parts under the floorboards. This also will catch any excess brake
rudder pedal, remove the bolt, nut and washer where the brake
cylinder clevis is secured to the rudder pedal.
Wipe off top of master cylinder. Using snap ring pliers, remove the snap
the top of the master cylinder.
moving parts Pull up on the shaft and remove it and all internal parts of
the master cylinder as
assembly. Wrap the assembly in a clean cloth to prevent dripping fluid and
take it to the
experienced Beech Lister, John F., who also happens to be an A&P, offers
the following additional thoughts:
I can't recall one ever going bad. If you must, you can
also carefully unfold the brass around the
"o" ring, and replace just the "O" ring, and
fold the brass back, and not replace the whole mechanism.
I have had good
luck just using regular "O" rings from the local Nat'l
Air Parts Association Store (aka NAPA....LOL)."
not replacing that molded "O" ring at the bottom.
The valve piston as Arky calls it.
Here are some thoughts from Beech Lister and A33 owner John
P., who had a pretty surprising experience with the "valve piston":
I did have one of these valves go bad about a year ago! The
O-ring had popped out of the crimp when I set the parking brake during an engine
run-up prior to take off. The result was it trapped all the pressure in the line
and locked the brake up. Had to shut down, open the bleed valve at the brake to
relieve the pressure to taxi back to the hanger.
When I got a rebuild kit from Johnston's Aircraft in Tulare,
CA ($68ea, don't have the part number here at work) it came with a different
style valve. There was "NO" O-ring...just a flat piece of gasket material glued
to the valve. Sorry I didn't get a picture of it!! Anyway, to me it seems like a
much better design that would prevent a failure like I experienced.
During my T-34 days with the Navy part of our landing checks
were "Brakes Pumped Firm". If this o-ring fails airborne from pumping the brakes
like this, or even after take-off to stop the mains prior to retracting the
gear, one would sure be in for a surprise at touchdown!!!
Beech Lister, Stan S. offers
the following comments from his experience:
"We are in the process
of re doing three master cylinders. Thought we could do them in place but
can't push the piston rod assembly down far enough to install the snap rings
in place because there is not enough room to do it in place, so we removed the
master cylinders. Avstat has overhaul kits for various master cylinders that
cost us about $56 each, and consist of 100% RAPID documented parts, even the
o-rings. The kit includes the o-rings as well as a wipe and another part that
I can't remember the nomenclature.
Avstat's kits did not
include new snap rings. Also recommend you get covers for the brake line
coming down from the reservoir, the upper line going into the master cylinder,
so the fluid doesn't all leak out while the master cylinder is removed. If you
use new snap rings be certain to use genuine Truarc,
we got new snap rings (not Truarc) that are plated and .37 thousands in
thickness and the Truarc are .32 thousands. Truarc snap rings are steel, and
not plated. After we finished up and started bleeding, a snap ring came off.
Now we have to remove the three master cylinders and install the thinner
Truarc snap rings. If you don't hear the snap rings snap into the grove nicely
when installing it, the snap ring you are using may be too thick and can come
off. This would not be a good thing when operating your airplane.
I recommend replacing
everything in the master cylinder, which you get with Avstat's kit. Why go to
the trouble of opening it up and not doing 100% of it?"
7625 Hayvenhurst Avenue Suite 18
Van Nuys, CA 91406
is a creative CSOB master cylinder plunger cover solution
contributed by Beech Lister, Kevin O., host of the B2OSH
Margarita & Pizza Party and Debonair owner and Beech parts
maven extraordinaire. Thanks Kevin!
40+ Year Old Cover
A nice new cover for your master cylinder!
also reminds us that if you have a Bonanza with a VV-15-625
master cylinder, you're SOL, because it's no longer made or
supplied by Beechcraft. BUT, you can buy the VV-15-625-1 and
shorten the shaft and presto you are in business again.
Reportedly, the master cylinder with the longer shaft is only
the secret scoop:
straight 35 till the N model (maybe M model)
the top one is a VV-15-625-1
which is available from beech for $133.00. They started using it on the P
model and after----until the very latest airplanes (went to the Cleveland
the one at the bottom of the
picture is a VV-15-625 it was used on
the VV-15 -625 is no
longer available----but a Cleveland retrofit is available for around 8 or 9
hundred! (CSOB1 says: NO %$*$^$* WAY!!!)
NOW--the CSOB way to do this is
to cut off about a inch--so its the same length--thread it to the same
distance as the old one---and its a perfect match !!!---barrel and hook ups
are the same --shaft is not hardened so it threads easy.
Note: If you use this master cylinder info find, you must come to OSH and
personally thank Kevin O. for this info. You can find him every year at the B2OSH
gathering in the North 40.
a Baron Master
Cylinder Extract #1 and
Extract #2 to help you identify the O-rings required
on some of the master cylinders. Remember,
check YOUR illustrated parts catalog for the exact part numbers
for your serial number airplane.
Thinking about adding Co-Pilot
Brakes to Your Beechcraft?
This is what you'd be looking for
from the Salvage Sources.
it Beech made a kit back in the day to accomplish this with every piece
required. The PN is rumored to be: 36-58000-3