'39 Master Cylinder Rebuild

K

kensesc

Junior Member
I am trying rebuild my original '39 Master Cylinder, but can't get it apart. I've gotten the retaining ring out, but the piston return stop won't budge. In the Service Bulletin it looks like the piston return stop should just pop out with no trouble. Am I missing something? I have tried Kroil penetrating oil and heat, but nothing has worked so for. I don't want to pry to hard and damage anything. Any suggestions?
 
If the piston is that well seated within the bore, there's a very good chance that the cylinder is pitted / damaged beyond the reasonable point of rebuilding properly. NAPA sells a NEW cylinder for around $55 if you have an account with them. I have purchased many of these and found each one to be of very good quality.

Their part number: Part #: NMC M1050
 
I have used this cylinder from Rockauto. It seems better made than some I have had and it is relatively cheap.
Here is the make and part number.
DYNAMIC FRICTION 35555007 (355-55007)
A part number search finds it straight away.
Mart.
 
Mart said:
I have used this cylinder from Rockauto. It seems better made than some I have had and it is relatively cheap.
Here is the make and part number.
DYNAMIC FRICTION 35555007 (355-55007)
A part number search finds it straight away.
Mart.
Click to expand...

For under forty bucks, hard to beat. (plus shipping)
Like Gary, I'd like to buy an extra cap.
Back to op question... also be sure it's not one of those (very) old m/c's that has a stop screw, inserted through the reservoir. Then, with fittings removed from 'front' end, drive piston out (punch, pushing on all internal parts... they will all be discarded.) Don't be surprised if it's really stuck. But the cylinder could likely be serviceable.
 
It's probably rusted/beyond repair. I just read the maximum you can hone an Early Mustang cylinder is .003, a piece of paper is .004. So, I'm going to assume that .003 would be the maximum you could hone "any" master or wheel cylinder. Now, if it was an original Ford script cylinder that you wanted to keep original to the car than you could have it sleeved and save it but otherwise just by a new one. Try and buy one that comes with the metal cap and not plastic caps that can leak. Looks at Rock Autos choices and see if they offer one with that metal cap. With a single brake system, you want everything to be right. Nothing wrong with a single system if it's maintained properly
 
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