Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Clutch master cylinder problem

Hi, I've just changed my clutch on my '72 MGB (full kit), and I'm facing problem with my hydraulic master cylinder. The problem is that the piston is fully engaged in the master cylinder and I cannot remove it anymore. I've tried to clean the piston but even with a hammer, I cannot remove the piston from the master cylinder. Does anyone has had the same problem ? How can I extract the piston from the clutch master cylinder ? Should I resign in changing the whole master cylinder ?
LM max

I just recently rebuilt my master cylinder and had a similar problem. I used compressed air to "pop" the piston out of the bore. If you don't have an air compressor and a blower tool with a rubber tip on it - find someone who does. Its about the only way to get it apart without causing damage.
Jeff Schlemmer

If you use compressed air, please be certain that the open bore of the M/C is aimed at something that will absorb the impact of the piston and keep it from bouncing all over the shop. Jeff is correct, the compressed air method is the easiset (and perhaps the only) method to get the piston out, but it is also a rather dangerous method if the bore is not aimed in the right place.
Good luck - Dave
David DuBois

Yep, Dave - I did forget to mention that. Wrap the MC in a shop towel before you use the air method. This will prevent a short range missile fire. Actually, it wouldn't go very far anyway, but it'll stop the piston from getting beat up.

Jeff Schlemmer

If the cylinder is in the car & air is used be careful where all the fluid goes - all over the paint!! Firts silly question - have you removed the cicclip - I have had a car in with both ears broken off so it was near impossible to remove. Sometimes pushing the piston in & cleaning the outer area of the bore will allow it to come out after pushing it in & out several times.
Garth Bagnall

I had a similar problem on frozen brake calipers, but compressed air wouldn't move them. So, I took a pipe fitting from an old pipe that would screw down into the hole and threaded it inside for a grease zerk fitting. I pumped them apart by applying grease into the fitting. The hydraulics are hard to beat. It is slow and messy, but works.
M. Whitt

This thread was discussed between 27/11/2004 and 02/12/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.