Hot Rods Did I ruin my new Master Cylinder? Or, can I still run it?

A buddy of mine is running a GM style master under the floor of his 32 with no residual valves with no problems. I tried it and now my new master cylinder is leaking at the diaphragm where the plunger goes in.

Can I clean it up and run it or is it shot?

Thanks in advance.

-Ron

 

The rear cup or seal is defective. Rebuild or replace your master cylinder.

 

Sounds like time for a rebuild kit. Leaking seals will not repair themselves.
KK

 

Forgot to mention I will be running the residual valves this time around.

You can rebuild a Master? Where do you get the kit? Local auto parts stores have them?

 

The residual valves have nothing to do with your master cylinder failing. Most any auto parts store will have a rebuild kit, you need to give them the bore size of your master cylinder. If it is new as you say, I am thinking it's defective or a sub standard part that may not be worth rebuilding

 

You'll also need to check the pushrod that goes in the end,you need just a little bit of free play before the rod touches the piston,nothing more than a few thousands.

 

What brand master cylinder is it? I agree with badshifter on this one, it may be defective or a low quality part to begin with. I would check that out before I spent more time trying to make it work in my braking system.

 

It's a cheapo unit I'm sure. I think I'll switch it out for a better quality one. Any suggestions?

 

you can get a kit @ any autoparts to rebuild it or you can usually by a rebuilt one cheaper.

 

So I'm looking into just buying a new more reliable master and swapping it out when the residual valves show up in a few days.

Thought about buying one directly from the Chevy dealership but am not sure what to ask for. Then again, theirs will probably be the same overseas made crap I just bolted on.

What master do I want to buy and what should I tell the guy at the parts counter I'm looking for? Mid 70's Corvette?

 

Best bet is to remove your current Master Cylinder, measure the bore size and note the line fitting sizes. Take it to a reputable parts store, preferably one that has some one that will actually look through a catalog, and see just what master cylinder you currently have. Most have casting numbers on them that can also be cross referenced. Joe

 

If you buy a "new" unit, you can bet your butt it will be made off shore. Lots of bad in the box units.

With buying a rebuilt unit, there's a good chance you get a USA made unit that's been rebuilt by a stateside rebuilder. Better than a 50/50 shot at it being right.

The lack of residual valves aren't the cause of your leak.

 

I'd bet the cause of the leak was your initial bleeding of the master, pushing the rod too far on the first stroke can cut the seal in the front, no fluid there on the first stroke. I push the rod partially the first couple strokes when bleeding the master to get some fluid down the bore to lubricate it, then go crazy.

 

Thanks for the heads up guys. Plan to tear into it this week.