Tandem master disassembly?

[The Veg]

What's the trick to getting the piston assembly out of a Girling tandem mater cylinder?

[lotocone]

Working from memory, I think that once the reservoir is out there is a large Allen fitting that needs to be removed.
It is so big that I had to buy the Allen wrench. It might be about 1/2 in. I wish I had a manual to refer to, but it's not available right now. Hope this helps.

[The Veg]

Thanks Bob; I did see that fitting but didn't put 2+2 together that it would be in the way. Will have a go at it.

[tedtaylor]

do NOT fully remove the reservoir, only swing it off to the side !!!!

[lotocone]

Thanks Bob; I did see that fitting but didn't put 2+2 together that it would be in the way. Will have a go at it.

You're welcome sir. I hope the rebuild goes well.

In my case, I got the master cylinder sleeved with brass, but I guess it's not necessary unless there is bad scoring. The place I used closed due to retirement of the owner, or I'd recommend them.

Bob

[1owner69Elan]

I went through my tandem MC rebuild a few months back and got help on the forum.

See this thread:

lotus-suspension-f42/elan-federal-brake-master-cylinder-t36306.html?hilit=Master#p248875

[Lotusdavid]

If all else fails, I have a NOS tandem for sale!

[The Veg]

Update: got the big hexy thing out and with some doing, the piston nearest the pushrod came out along with a lot of sludgy black stuff that I presume was once the seal. The other piston is stuck way back in the bore at the moment, and the bore is well-coated with hard brown brake fluid residue crust, and I presume that this stuff is what's holding the other piston in place. Anybody have a favourite method for dissolving the crust?

[nmauduit]

Update: got the big hexy thing out and with some doing, the piston nearest the pushrod came out along with a lot of sludgy black stuff that I presume was once the seal. The other piston is stuck way back in the bore at the moment, and the bore is well-coated with hard brown brake fluid residue crust, and I presume that this stuff is what's holding the other piston in place. Anybody have a favourite method for dissolving the crust?

unless it has cooked solid, compressed air at the return valve port (where the MC tends to leak...) should push the slave piston out. You may want a piece of cloth to gather small parts before they get airborne...

[The Veg]

Yes, the air did get the piston out, but the question remains: what's the best stuff for dissolving the brown crust of fluid residue? So far I've had poor results with penetrating oil and with mineral spirits.

[nmauduit]

Yes, the air did get the piston out, but the question remains: what's the best stuff for dissolving the brown crust of fluid residue? So far I've had poor results with penetrating oil and with mineral spirits.

I don't recall how bad it was on mine when I cleaned it up, but I spent some time fine wet sanding with the mineral oil to smooth out the color changes. The way I did it was rolling a new sheet of fine (1000) paper all the way inside the bore and unrolling it inside to do the smoothing, so that remaining lines would not be long the axis (direction of leaks) - that repeated a number of time with cleaning in between. I did not clean it up 100%, just to the point it looked smooth under close scrutiny with a led (a bit like gun bore inspection) and the discoloration (oxidation spots) seemed small enough and not located where the pressure would occur (e.g. in front of the master piston, rod side). I have then switched the system to silicone (DOT 5.0) to avoid internal oxidation from absorbed moisture.

So far this has worked for me... but I don't know if the smoothness level achieved will lead to more frequent rebuilding.