View Full Version : Brake Master Cylinder

12-21-2007, 11:27 AM
I managed to get the Brake and Clutch master cylinders from the PO yesterday.

The clutch master seems to be in good condition. I can manually actuate the cylinder, and the piston returns (I assume from the spring inside).

The brake master cylinder doesn't seem to be in such good condition. I'm unable to get the piston to move inside the cylinder. It seems stuck near (if not at) the bottom (or back) of the cylinder. I've tried compressed air to see if that would make it move but no luck.

Any suggestions on how I might get the piston out of the cylinder? I thought about running a short line from the clutch cylinder outlet to the brake cylinder outlet to see if I could make it move, but I think the fluid would just flow out the inlet on the BMC.

12-21-2007, 11:46 AM
Apple Hydraulics. Looks like $95 for your car. Money well spent, in my opinion.



12-21-2007, 12:32 PM
Out of stock, but TRF had one, for a few dollars more.

I figured with the piston seized it was probably not worth trying to save, but wanted to make sure I wasn't missing something obvious.

12-21-2007, 12:45 PM
Depends on how tightly the piston is seized and how much damage you do getting it out. I've saved several where the piston was too tight to blow out with compressed air.

Lots of valid techniques, but my favorite is to fill the inside with as much carb cleaner (or any volatile solvent) as I can get in, then block both ports with bolts & nuts. Clamp one ear in a vice or similar, then commence heating the body evenly with a propane torch. The aluminum body will expand, increasing the clearance to the steel piston (and reducing the damage the piston will do as it comes out). Plus the solvent boils and generates pressure inside, which will eventually force the piston out.

It does tend to be rather er, exciting when the piston does let go, so make sure it's pointed somewhere harmless and you are wearing eye protection. There may even be a small flash of flame as the solvent vapor burns (but it goes out instantly). One of the pistons from my 56 is still in the rafters somewhere ... I'll have to climb up there and look for it some day /bcforum/images/%%GRAEMLIN_URL%%/grin.gif But both MCs were well and truly stuck when I started, and both of them appear to be reusable.

BTW, the replacement MCs are visually different than the originals. They work OK, though.

12-21-2007, 01:31 PM
Hmm... I will try that tonight. Am I to assume then that the threading on the master cylinders are 3/8th fine thread (i.e. -3 AN)?


12-21-2007, 01:37 PM
Definitely NOT an AN fitting, but the thread is a standard SAE fine thread and might be 3/8".

12-21-2007, 01:57 PM

I tried Randall's method once, but my ear really hurt when I clamped it in my vice!

12-21-2007, 02:06 PM
Ah-ha... SAE is a 45 degree fitting and AN/JIC is 37.

I'll be sure to use the correct fittings.

12-23-2007, 12:36 AM
Wow... Randall that worked like a champ. I even used the technique to disassemble the clutch master, which now that both are apart, is much the worse for ware.

I've got a rebuild kit and a new master on the way, so I should be able to make two good working masters from the lot.

12-23-2007, 01:03 AM
I tried Randall's method once, but my ear really hurt when I clamped it in my vice! That's nothing, wait til you try heating your body with a propane torch until your piston pops out !

12-23-2007, 01:24 AM
As you get older you will have more appreciation for that technic.

12-24-2007, 11:40 AM
I tried Randall's method once, but my ear really hurt when I clamped it in my vice! That's nothing, wait til you try heating your body with a propane torch until your piston pops out !

Don't you have to apply the brake cleaner first? /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif

12-24-2007, 11:45 AM
Just don't get it inside the ear. Outside is OK.

12-24-2007, 05:22 PM
You guys are going to get this thread shut down by Mickey or Basil if yer not careful!

12-25-2007, 11:29 PM
Allright then... I'll keep it on track...

I'm having a hard time finding the fittings for the ends of the master cylinder to resevoir line. I managed to find a brass fitting that threaded on perfectly to the nipple on the resevoir in the pipe section of Home Depot after coming up bust at Autozone.

At the other end, I haven't had such good luck. It seems it difficult to find (locally) a 1/4 pipe fitting that threads into a 7/16th hole.

Anyone recommend a online vendor that might sell just the pieces I need? I ordered a complete hand bent pipe (for the clutch master) on TRF, but it didn't come anywhere near fitting properly, and the pipe I bent up (with my new tool) looks and fits better.

12-26-2007, 11:04 AM
I got all my tubing (brake and clutch) from Classic Tube.


The fittings and lengths were all correct, but I did have to do some minor bending to make everything work.

They should have the fittings you need if you're going to make your own lines.