C3 Master Cylinder Rebuild

[James W.]

I'm in process of rebuilding my "509" DC standard brakes master cylinder for my 1972 coupe. I'm in need of a secondary piston. The primary piston comes in the rebuild kit, which I've already purchased. I've looked around a little, but haven't found anything. Does anyone know where I could get one of these short of purchasing a used master cylinder? Does any of the aftermarket master cylinders have an equivalent secondary piston?

Any help is appreciated.

Thanks,

Jim

[Joe L.]

Re: C3 Master Cylinder Rebuild

Jim-----

The secondary piston that you're looking for was GM #5460413. Unfortunately, it was discontinued without supercession in May, 1987.

I don't think that these secondary pistons are commonly available in the aftermarket. I think that commercial rebuilders must have a source for them, but they only use them when necessary to rebuild master cylinders and they aren't otherwise sold.

The good news is that the parts from non-GM master cylinders for the same application will usually interchange. Of course, purchasing a new aftermarket master cylinder is going to be an expensive way to get this piston. However, you can purchase a rebuilt master cylinder for your application for, usually, a rather modest price. Then, you can "scavenge" the part from it. If you're lucky, you might even get another '509', "DC"-coded casting in the process which you can keep for a spare.