Master Cylinder Refurbishment

[ExMODtraveller]

Hi I have just removed and replaced the insides of the master cylinder, before putting the rubbers back inside I greased them with brake fluid so they would slide in easy but when I press the brake pedal down to bleed the system, it doesn't want to spring back itself? Is this normal until it is bled? Thanks

[bmcecosse]

Have you attached the return spring?

[ExMODtraveller]

yes I have attatched the pedal return spring haha

[bmcecosse]

Well - it should come back -unless the pedal is simply too tight on the shaft. If you move the clutch pedal - does the brake pedal move with it?

[simmitc]

Is it the pedal sticking, or the piston? Did you check operation of the cylinder before refitting it? The piston should move freely, springing back into position after pressing home with a suitable rod. I hate to say this, but if it was working before you serviced it, then the chances are that something is not quite right with the reassembly. Did you check that the bore was clean - rust will stop it working properly.

[kennatt]

another reason for fitting a new cylinder,from expirience,every time over the last 30 years,that I have been forced to just re rubber a master or slave cylinder,after a short time they go again. For me just not worth the risk,steering and brakes = new units and where you can afford it ,not copies.
If you look inside the master ,If its the original ,and many are because they used to last for many years,there will be a rough pitted area on the bottom where water,in the fluid, has cause an area of corrosion,its just outside of the swept area of the piston,which has kept the bore clean,its very difficult to clean up this area,and as soon as the rubber get pushed over it,as in bleeding,then the lip of the seal gets damaged and well you know the rest
Some suggest honing the bore,but for me this increases the size and the rubber dosen't seal as well .

But each to their own.

[Declan_Burns]

I would also advise fitting a new master cylinder and not refurbishing an old one for the same reasons mentioned by Kennatt. The new master cylinders are ever so slightly wider and may need dressing with a file or be ground to fit inside the chassis.

Regards
Declan

[les]

Yes, it must be very difficult to produce something the right width.

[Declan_Burns]

Correct Les,
but that's the repro world. I think there's an element of "yellow fever" involved!

Regards
Declan

[SGTBILKO]

Can't they get anything right? Oh for the good old days of reliable parts manufactured in Blighty!

[kennatt]

yes but at least parts can still be found, if you had to have an item made as a single unit,would cost more than the car was worth.

[SGTBILKO]

I agree with the above but one has to admit that there are problems with repro parts and when it comes to brakes, I for one would prefer that they were perfect.