With our Grob G109B motorglider the wheel brake master cylinders are an item
supplied by Tost at www.tost.de . We have been able to buy replacement seal
kits and replacement master cylinders from Tost easily. No hassle. The
Tost people may have their catalogue on-line for perusal.

Possibly the master cylinder for the Grob G103 is also available from Tost.
There are a few variants. My faint recollection is that the G103 has a side
lever actuation rather than a top lever actuation, but my memory could be
imperfect.

The master cylinder in the G109B is the same as used in the hydraulic disc
braked mainwheel installations in our Janus B (which we converted to
hydraulic disc brake from drum brakes using a kit from Tost), Janus C (which
came so equipped from manufacture), etc.

Tost also can supply a five page document headed "Disc brake systems -
Maintenance" and subtitled "Service and maintenance of disc brake systems
with master brake cylinder of type 3,4 6 and 7". This document assists with
info on bleeding. I think they would be happy to email it to you if you ask
nicely. They sent me a copy when we were installing the Tost kit for
hydrauilic braked main wheel system into our Puchacz. (Best thing we've
done with our Puchacz maintenance and operations wise was getting rid of the
Polish mainwheeel and wheel brake.)

I agree with JJ Sinclair that bleeding these systems can be a bugger.
Whereas by contrast with our Piper Pawnee it is easy as pie, so to speak.
With a Tost master cylinder in the system, you have to have the brake lever
as far towards brakes off as it can be.

Hope this helps.
Roger Druce
(Australia)


"JJ Sinclair" wrote in message
...
Ray,
I have found it very difficult to bleed the G-103 master cylinder. The old
*hold pressure with the dive brake lever and open the bleeder valve* has
NEVER
worked for me. The only thing I have found that works is to *pressure
bleed*,
form the wheel bleeder valve, up through the master cylinder.
Hope this helps,
JJ Sinclair