|
AUSTIN
HEALEY POWER BRAKE SERVO REPAIR NTAHC
WINDMILLS AND BRAKE SERVO UNITS No, this Texan has not been eating Loco weed. There is a connection between windmills and brake servo units. The trail of events leading to the sources of key components missing in a brake servo repair kit is quite unique. After suffering
a servo unit failure, I assessed the damage. All that is needed is a
repair kit. Wrong ! Because Kay and
I planned to attend the Southeast Classic in Ashville, NC, I was reading
a story in Healey Trails (North Texas AHC newsletter) about a past Classic.
On the very next page was an article, "Restoring The Brake Servo Unit
Vacuum Cylinder" By Richard Strunk. Richard provided the solution to
the statement in the shop manual "No lubrication is needed for the piston
seal as the seal and cylinder are specially treated during manufacture."
The dry film coating that Sandstrom Products Company sells is 26A. This product works well for recoating the inside of the servo vacuum tank. A phone call and $15 brought a spray can to my door. Now for the WINDMILLS.
On a trip to Red River, New Mexico (in my BJ 8 of coarse), I recalled
discussing with a friend, his unusual business. He sells windmills to
many of the Indian tribes on the reservations in New Mexico to pump
water. One of the major replacement parts is the leather cup used in
the pumps. After many unsuccessful attempts to purchase a new leather
seal from Healey parts sources, I called Beck Aitkinson and asked where
they bought their's. He said "one of the few sources is A-1 Gasket Company
in Fort Worth, Texas." This company will make an exact duplicate of
the leather seal. This relates the unique trail in search of some missing
components in repairing my servo unit. The following are some special operations and repairs that will supplement the workshop manual repair procedures. After performing the special operations, I suggest you assemble the servo according to section MMM.15 of the workshop manual. The two plastic air valves showed some wear on their seating surface. I am told you can swap one for the other and reassemble them in opposite holes to compensate for wear if they aren't worn to greatly. You can also use very fine emery paper and a flat surface to help true the sealing surface. I did not use any
of these methods. Instead,
I used a lathe to chuck the valves in and turn a true seat on the face.
I think that truing the valves on a lathe is the most precision method
to ensure a good seat for proper operation of the servo. Your
goal in retruing the valve seats is to obtain a non leaking air valve
seat. The two seats in the valve body where the plastic air valves make
contact should be true and free of pits. My unit had some pits caused
by corrosion. If the surface
is not badly worn or corroded you can use a piloted counterbore to resurface
them. To spot face the seats you need a piloted counterbore of the proper
dimension. The operation in its simplest form is accomplished by holding
the body square with the counterbore in a vertical mill or good drill
press. Using a low RPM, to eliminate chatter marks on the seat, start
the pilot on the counterbore into one of the holes. Lower counterbore
until you cut a good true clean seating surface on the valve body seat.
Remove as little material as possible. If this sounds like to much for
you to do, or you don't have the tools, take it to most any machine
shop to have it done. If by chance your valve body seats can not be
salvaged by this method, have a machine shop bore and rebush the seating
area. As mentioned, Richard
Strunk has done the detective work on the dry film lubricant for coating
the inside of the large vacuum cylinder bore. The Sandstrom 26 A product
works very well. The cylinder bore should be super clean before spraying
light coats of dry film lubricant on the bore diameter. A word of caution, if your leather seal has been exposed to leaking brake fluid it must be replaced. Tom Taff was rebuilding
his servo unit and I let him use some 26A to coat his cylinder. Because
the leather seal had absorbed some brake fluid, when he assembled the
unit, the remaining fluid in the leather attacked the coating. The most
important part is the leather seal in the vacuum cylinder. Most importantly,
because I know of no Austin Healey parts supplier that sells them. The A-1 Leather Gasket Company of Fort Worth, Texas can supply them for about $30. They are made of leather to the same dimensions and thickness as the original. I have talked to them about this application and they will know what you want when you contact them. The leather seal
on your piston can be removed by prying the retaining ring off toward
the aside that has the valve stem rod attached. The new leather is assembled
by pressing this ring on until it holds and seals the leather cup. The
foam rubber material included in a servo repair kit is, and probably
will remain in future kits, much too large. When this material is placed
under the leather cup it will cause to much pressure on the lip of the
cup. This increased pressure will not let the piston move freely for
proper operation. Therefore a smaller diameter foam backing ring must
be used. Tom Taff found some ¼" round material that works very well.
This material was purchased at Home Depot. I hope the information and sources will help in repairing your servo and keep your Healey healthy. Drive it ! Sources: |