1976/7 924 master cylinder

[vitesse]

Started refurb on my friend Mike's car's master cylinder after it drained all it' s fluid over the lockdown.
It's the ATE dual piston version with circlip at the piston rod end retaining the innards & has the clamp bolt centrally fitted which once removed along with the internal circlip should allow the piston assembly removal.

Only it won't-the circlip comes out followed by the steel washer & the end rubber seal behind which is a nylon washer ( not mentioned in the Haynes manual covering this earlier model & not even discussed in the official workshop manual,it only says replace the master cylinder )-it feels as if there is another bolt somewhere but there isn't .
I can't believe that this is caused by say one of the internal seals/ backing steel washers catching on some groove or other that isn't visible.

Does anyone have any ideas please - don't want to use more force & cause unnecessary internal damage.

 

[vincematthews]

Started refurb on my friend Mike's car's master cylinder after it drained all it' s fluid over the lockdown.
It's the ATE dual piston version with circlip at the piston rod end retaining the innards & has the clamp bolt centrally fitted which once removed along with the internal circlip should allow the piston assembly removal.

Only it won't-the circlip comes out followed by the steel washer & the end rubber seal behind which is a nylon washer ( not mentioned in the Haynes manual covering this earlier model & not even discussed in the official workshop manual,it only says replace the master cylinder )-it feels as if there is another bolt somewhere but there isn't .
I can't believe that this is caused by say one of the internal seals/ backing steel washers catching on some groove or other that isn't visible. Does anyone have any ideas please - don't want to use more force & cause unnecessary internal damage.

You don't say so but I assume you have removed the central bolt? Does the piston assy move freely in the bore? I'm not sure if it would be possible to rotate the piston assy in case it's sticking in one orientation.

Otherwise block off the other ports and connect an airline (safety precautions) to the furthest in port and see if gentle air pressure gets it out. The forces involved in the hydraulic system can be considerable so I wouldn't have thought you'd do any damage to it.

Was it drained down for long enough for corrosion in the bores to be an issue.

I hope he's going to let you drive it after this labour of love!!

 

[vitesse]

Yes,Vince,the centre bolt has been removed -the operating rod can be pressed in & one can see the piston moving through all the fluid tank,centre bolt holes but the innards will just not come out when pulled -it just feels like its held by some physical stop but I can't work out what it can be unless the stiff nylon washer is swollen by fluid contact & is hitting the groove or holes.
Will try more force by gripping the pushrod in a soft jawed vice methinks.