Parts for 65 PB MC

[William Holder]

Hello All,
I am rebuilding the Master Cylinder from My 65 coupe. Disk Brakes, Power brake. The cylinder is good and will clean up well but the pistons have a little corrosion on them and I would like to replace them. The rebuild kits that I can find only have the seals. Does anyone know where I can find either a rebuild kit that contains the pistons or the pistons themselves? I have look in all the catalogs I can think of and no luck. It appears that this is 65 and 66 only part. Does anyone know it the pistons from another year (or Vehicle) 1" MC would work?
Thanks
Bill

[Joe L.]

Re: Parts for 65 PB MC

Bill-----

I don't know of a source for these parts. They have not been abailable from GM in many years. As far as I know, they are not available from Raybestos, Wagner, or Bendix which are the major manufacturers of brake repair parts. In addition, I don't know of any other application which used the same internal parts as these 65-66 PB master cylinders. Actually, I don't understand why since the 67-76 1" master cylinder is basically the same except for the "cover" system. However, there must be some other difference with respect to the hydraulic components and configuration.

The only thing that I could suggest would be to contact a brake master cylinder rebuilder like Stainless Steel Brake Corporation, Vette Brakes, Apple Hydraulics or White Post Restorations. If they don't have them or know where you can get them, then I'd say they aren't out there.

[William Holder]

Re: Parts for 65 PB MC

Thanks Joe,
I may by the later kit with the cylinder for a 1 " bore and measure the parts the pictures that I have seen look Very simular.
Thanks again you are a great asset to this hobby. I really appreciate you and your seemingly endless knowledge.
Bill

[Joe L.]

Re: Parts for 65 PB MC

Bill-----

Keep in mind that the kits for the later master cylinders are supplied with only the primary piston and not the secondary piston. The secondary pistons for even the later master cylinders were discontinued by GM a long time ago. However, I believe that they have come back on the market as a reproduction or replacement item. I don't recall the source, though. As I vaguely recall, it's not one of the traditional, major brake parts suppliers, though.

[William Holder]

Re: Parts for 65 PB MC

Thanks Joe,
Do you possibly know which one is primary and which is secondary ? Only one of them is really corroded where the spring from the other piston has been against it. IS the secondary one the one you have to remove the bolt (from inside the resivoir)to get it to come out ?
Thanks again
Bill

[Joe L.]

Re: Parts for 65 PB MC

Bill-----

Yes, the secondary piston is the one you describe. It is the forwardmost piston. The primary piston is removed from the master cylinder first, followed by the secondary piston.

[William Holder]

Re: Parts for 65 PB MC

Joe,
OK I got it thanks. Wouldn't you know the secondary one is the one that is corroded the worst ! Im going to go look now but I am pretty sure that is the one that I need. Thanks again for all your help.
Bill

[Joe L.]

Re: Parts for 65 PB MC

Bill-----

Actually, corrosion can be a problem with either piston, particularly when glycol-based brake fluid is used. This fluid is very hygroscopic (absorbs atmosperic water). Coupled with the fact that the pistons are aluminum and the master cylinder body is cast iron, there are all the right "ingredients" for corrosion. Chances are, if the piston is corroded, the master cylinder bore will be, too. You might not be able to see it too well, but I'll bet damage is present. ANY master cylinder bore damage requires sleeving. I DO NOT RECOMMEND trying to hone a master cylinder bore.

[Frank C.]

Re: Parts for 65 PB MC

Hi Joe..what's your opinion of DOT 5 Silicone Fluid? I've been using for about 15yrs and only seen positive results and always looks like the day I put it in.

[Joe L.]

Re: Parts for 65 PB MC

Frank-----

That's what I use in the 69.

[William Holder]

Re: Parts for 65 PB MC

I agree Joe . However the coroosion is not on the sides of the piston where it meets the bore but on the end of the piston where the spring from the other piston was riding against it. The sides and seal areas look good In fact I think it would work ok right now I am just worried that the corrosion on the end will someday spread to the sides/bore area. Amother interesting thing I noticed there was a salt of some kind had formed crystals in the middle of the piston between the two seals? Again no corrosion there just these funny dark grey crystals filled up almost all the space between the seals on the bottom edge. It would be interesting to have that analyzed to se what it is and where it came from?
Bill

[Joe L.]

Re: Parts for 65 PB MC

Bill------

I would suspect that the crystals you are referring to are a deterioration product of the glycol fluid. Either that, or they are the reaction product between the fluid and some contaminant that got in there.

As far as the piston goes, if the corrosion is limited to the end of the piston at the contact point between the spring and the piston, I think that you should be able to carefully clean that up and have no further problem with it. Where the problems occur is at the PERIPHERY of the pistons, where it contacts the bore. If there is corrosion damage in this area, there will be bore corrrosion problems and damage. If not, the bore may well be just fine.

One other problem, though, involves wear on the pistons, themselves. You will note that the pistons are hard-anodized and will have a "yellowish green" appearance. Carefully examine the PERIPHERY of the piston and note if there are areas in which the anodize is worn through. You will be able to tell because instead of the "yellowish green" coloration, worn areas will show a "silvery" color (i.e. bare aluminum). If any of the hard anodize is worn through, the piston should be replaced. However, if you can't get the pistons, you will have to reuse what you have and hope for the best. There's no way I know of to "rebuild" the pistons.

[William Holder]

Re: Parts for 65 PB MC

OK Joe,
I will look at them more closely. I thought about having them made from the ones I have as a pattern but I am sure that would be very expensive and hard to do to the tolerances necessary. I will still try some of the people that offer rebuilds and maybee even just send it to them.
Thanks again for all your advice.
Bill