Where's my brake fluid going?

[farrier]

Now I think it's the rubber plug not sealing with the master cylinder. This is a rebuilt from auto parts store.
I had a spare master cylinder still connected to a parts truck. 1980 with electric connections. Reservoir and rubber plugs not leaking and holding fluid.
Put the old plugs and reservoir on the rebuilt mc (1981 pickup) and it leaks the same way.
I do see that the rubber plug when installed in the mc has a little slop when moved from side to side before I install reservoir.
Any way to seal this or expand somehow? I guess I can buy a new mc instead of rebuilt but that would take a couple days to get.
Thanks.
Can I just swap out the mc from my '80 and put it in the '81? Even though the '80 has the electric plugs?

[TylerDurden]

I read somewhere on the webz that the MCs got changed:

...personally id find find german pedals, booster and master since replacement westy masters suck arss on how the bottle mounts.. they changed the grommet design so seem to leak brake fluid between bottle and master... and me not found a cure...

If there were a cure, I imagine the writer would have found it.

further:

81-84 westy caddy = westy caddy.. different then non westy cars. aka german aka jetta, cabby, rocco of 81-84 is different..

6 port... means NOTHING.. originally they were 4.. since brake light switch on pedal vs german on master... but replacements came in 4 or 6 versions... 84ish german versions moved the switch to pedals around same time they went donut/trunk floor change..

pic of master by booster to determine which you have.. how 2 mount are different...

booster, pedals, master are all different... german vs 81-84 westy... if someone swapped any of it.. as matched parts = my not knowing what you have... aka 5 speed to auto swap.. brooken booster so on...

google on any of that for more...

[farrier]

Well I went ahead and swapped the rebuilt for the spare I had.
No more leaks. Stops great. Life is good.