How to remove stuck rear brake master cylinder piston?

[OrangeUtopian]

This 79 Jota (original LHS brake - rearsets) has been standing for a decade or more.  Rear brake master cyl. piston is stuck tight.

I can buy a new piston & seals but here's the thing, how do I get this one out ? 

Paul.

 

[sfcpiet]

You need a long, thin drift that fits through the hole where the banjo is fitted.  Tap the piston out from there.

piet

 

[Dellortoman]

Shouldn't need more than a push by hand. I use a pin punch. About 4 or 5mm dia I think.

 

[Grant]

If it is seized then soak liberally in penetrating fluid beforehand.

 

[Ventodue]

You need a long, thin drift that fits through the hole where the banjo is fitted. 

AKA, 3" nail with the pointy bit cut off ...

 

[Simonr501]

As Piet says - long series pin punch from behind the piston.
The piston is secured by a crush washer and seal at the other end, you need a reasonable knock to get it out.
When you fit the new piston and seal you might need a bit of clean and smooth pipe or tube to hit and expand the new crush washer within seal to stop the piston spitting out on its own - don't hit the drift/pipe/tube too hard and expand the crush washer too much or the piston will be too tight.

 

[CLEMTOG]

put it in a pot of water and boil it for ten minutes, then (with gloves) place it in your pinch vice and knock it out with a pin punch that is the biggest you can get through the hydraulic port.
CLEM

if you haven't got pin punches then but a set, more work is ruined by not having the proper tools than almost anything else

 

[piranha-bro2]

I like the heat idea too, Clem. If there's any seizure inside it could damage the alloy cylinder just whacking out out. Or a good soaking, as Grant suggests.

 

[Dellortoman]

put it in a pot of water and boil it for ten minutes

Then throw in some vegetables, a stock cube, season to taste, and enjoy a bowl of Brembo soup.

 

[DaveB]

AKA, 3" nail with the pointy bit cut off ...

+1, but put a cloth or bag over the lever end of the piston, lest you have to go searching for the piston and the spring.  I speak from experience.....

 

[OrangeUtopian]

Many thanks for all that helpful advice!

Couple of nights soaking it in WD40 and a 4mm punch did the trick quite easily with the unit held (gently) in a vice.

 

[Legs]

I used an old aluminium tent pole to seat the new piston, worked a treat. Be sure that the washer is fully seated otherwise you could have leaks.

 

[hooksey]

I used an old aluminium tent pole to seat the new piston, worked a treat. Be sure that the washer is fully seated otherwise you could have leaks.

Bit of half inch copper tube with a flare  perfecto !

 

[Laverdalothar]

In the "Hints and Tips/Wiki" area, you can find:

https://www.laverdaforum.com/forum/index.php/topic,82062.0.html

though it is for a front master cylinder rebuild, most of the steps are the same on the rear one.

cheers

 

[CLEMTOG]

don't knock it in too far, use the alloy quadrant as a guide to getting it in just right, knock in a bit, remove punch and trial fit the quadrant, until just right, usually a deep socket of the right OD will work, but a turned steel drift is very much better, don't forget to aneal the copper washers when you refit the hydrauilics, OH and lube the pivot prior to assembly.
CLEM

ps wait, for it, wait for it, wait for it...next question is ..... how do I get the air out of the (bleeding) calliper