BRAKE MASTER CYLINDER OVERHAUL

I own a 1983 Austin Mini Mayfair and noticed that the brakes are getting soggy. I’ve replaced the brake shoes and wheel cylinders in the last couple of years and after bleeding out the brakes I normally get a good pedal.

Last month I replaced one of the front flexible brake hoses and since then I have had difficulty getting the brakes to bleed out properly. However much care I take, there still seems to be a small number of air bubbles from the bleed screw.

This coupled with the fact that the brake fluid in the reservoir is tinged with black has led me to believe that perhaps the master cylinder seals are failing. Although I can get a new brake master cylinder, I was hoping to save a bit of cash by just replacing the seals. Is this a viable option or would it be false economy? Alan Taylor The brake master cylinder on your Mini is quite a simple unit and providing the bore is not showing signs of wear or any score marks it should be quite feasible to re-seal the unit. The brake seal kits are readily available and providing you are methodical about the process, then the job should go smoothly.

Ensure you have a clean area to carry out the job and be warned that the brake fluid is harmful to painted surfaces and so any contact with the vehicle should be avoided. Once the piston has been removed from the cylinder, the bore of the master cylinder should be thoroughly checked and if any scoring is present then I would consider fitting a new cylinder.

Ensure the components are cleaned to remove any of the debris from the old seals and when fitting the new seals, lubricate them with fresh brake fluid before assembly. Once all fitted back into position the brakes should be bled out slowly and methodically.