bluestreak63

Working on overhauling the drum brakes, new drums, wheel cylinders, shoes, springs, etc. In looking at the MC, it looks like it could use a refresh. Was just going to buy a non-GM numbered replacement from a Corvette vendor and shelf the original. Then realized a simple Raybestos MC36242 would work as well and is cheaper. Anyone use one of these before? Any issues with them?

In looking at the shop manual, looks like it's as simple as removing the clevis pin and removing the nuts to the MC under the dash?? And then the MC should just come right out.

Does the rubber boot (under dash) need to be replaced if it looks fine?

This Raybestos MC looks like it comes with the foam gasket, but I think I still need the firewall gasket. Any other misc parts that I'm missing that I might need? Probably will replace the mounting bolts and nuts too.

tbarb

If you have the original 1963 master cylinder on the car I suggest keeping it on the car, they are pretty pricey these days. Does the cylinder leak, if not just paint it flat black and reuse it.

That being said there is no need to go under the dash for anything except adjust the pedal free play per the assembly manual. If you remove the bolts at the firewall the M/C should come right off and the clevis and rod will stay in the car.

The rubber boot is fine to reuse.

MikeM

See Centric and Dorman MC's at the bottom of the list. Only look for 7/8" bore size cylinders.

You can just put a seal kit in your old cylinder if it's not worn or pitted.

Rich Yanulis

I just put a rebuild kit in mine, it works 100%.

Should be good for another 50 years

MikeM

I forgot to post the link. Go to Rock Auto web site and search for a MC for your car.

bluestreak63

It is the original, so I will be keeping it. I'll take some pics later today and post them up. When you see the pics, you'll understand why I want to just replace with an aftermarket.

But I guess if the bore is not pitted, I could rebuild it. The issue is that it's kind of rusty. Could I just take the MC apart and put the main unit in some evaporust? Didn't know if that was the correct approach. I don't have a blast cabinet.

MikeM

Here is what I do with a rusty cylinder.

Mix up a 10-1 solution of water and 30% muratic acid. Strip the cylinder of the guts and drop it in the acid solution. After 10 minutes or so pull the cylinder out and rinse it. If the rust isn't gone it's back in the acid for a few more minutes.

Rinse it off and scrub with Castrol Super Clean and blow dry.

Get a small wad of Scotch Brite pad and wrap it around a drill bit. Shove the SB in the bore and start the drill, moving the pad back and forth. After a few passes, you'll have a nice clean bore. You can then inspect for wear and pitting. If the bore needs honing you can do it now.

Before it comes up, yes I know about the effect acid can have on metal. So far, using my method I have had no problems and don't expect any. I have cleaned all sorts of engine and chassis parts using this method. I not advising anyone to do it, just what I do.

jim lockwood

Mike, have you ever used phosphoric acid for rust/corrosion removal? I have no experience with muriatic acid and am wondering how the two compare.

Jim

MikeM

I tried a trial with Phosphoric acid. I think it was on carburetors. Don't remember though. I know I have a almost full bottle left so whatever I was trying to do must not have gotten me to the moon.

Muriatic acid WILL eat cast iron up so you have to be careful when soaking. Muriatic acid solutions will clean many metal parts on a Corvette. I think it's aggressive enough that a person shouldn't douse any valuable metal parts in it until he gets a handle on how his solution works.

Muriatic 30% acid is used to clean swimming pools. You can buy it at WalMart or any pool supply place..

bluestreak63

So here is what I am dealing with. Never used muriatic acid before and I would hate to screw something up. I've used evaporust with good success before, so I'm wondering if I should try that first.

I guess a rebuild kit would be cheaper and then I don't have to shelf the unit. Looks like the shop manual has a write-up on the rebuild.

So besides the rebuild kit, I should probably get the firewall gasket and probably some new bolts and washers. Anything I might need while I'm putting in the order?

jim lockwood

Thanks, Mike. I'll give the muriatic acid a try on something I don't care about.

I've used phosphoric acid with great success on aluminum and pot metal FI parts. So I'm comfortable with it and know what to expect.

On rusty steel and iron, phosphoric acid affects the rust but it seems to need help. Being a lazy sort, I don't want to offer the help if I don't have to.

Jim

bluestreak63

So the MC cleaned up pretty nice with the Evaporust product. Safe, non-toxic, biodegradable, etc. I have a rebuild kit on order UP393 from Napa.

The bore looked nice and smooth, no pitting.

The date code is A-5 3, that means January 5 1963 right?

Next step is to paint it. After rinsing the Evaporust off the MC, it flash rusted, any ideas on how to prevent that? Can I just rattlecan the MC with the light orange tint? Or should I re-rinse, dry and immediately paint?

From the research, it looks like the correct paint color is a semi-gloss black? I read Krylon had a product 1613, but it's been discontinued at the retail level. Any suggestions on a similar rattle can product?

Does the inside of the reservoir where the brake fluid goes get painted? I would think not, since the paint could get into the holes where the fluid has to travel and induce some blockage. Or do I just tape off the holes at the bottom of the reservoir, the nipple/flare outlet, and the bore and go nuts with the rattlecan?

tbarb

I think the correct black is like a stove black (flat), don't paint anything but the exterior. Keeping the original is a good thing..

tbarb

I also want to add that with fluid that looks the old/dirty, flush that system very good and inspect all the brake lines and hoses you can see. Keep it running until it's clear, we are talking brakes here and a important safety issue.

MikeM

I rinse in a bath of Castrol Super Clean followed by a bath in a baking soda/water rinse followed by plain water. Sometimes I follow with heating the part with a propane/butane torch to dry it quickly.

bluestreak63

Yeah, I'll be sure to bleed the system thoroughly. I also plan to bench bleed the MC before putting it back in.

The CSC won't hurt the cast iron? Just straight solution or mix? What does the baking soda/water rinse do?

MikeM

No, mix it with some water.

It "might" neutralize the acid if there is any in your rust remover. I use it with the Muriatic acid.

bluestreak63

Well a month later, still working on the brakes...

Took another look at the original MC and decided to just shelf it and have it rebuilt when I do the frame off restoration sometime in the early 22nd century...

That being said, I ordered a new Raybestos MC and will use that instead. Need to bench bleed and install.

My question is around the rubber boot that goes over the cylinder rod, is there supposed to be some sort of lubrication you are supposed to put on the cylinder rod? The boot seems like a tight fit over the rod and would seem that everytime you apply the brake pedal, the boot would get folded up...if that makes sense.

Frankie the Fink

The boot is sort of a bellows arrangement and should move in and out with the M/C push rod and therefore doesn't need any lube. BTW - '64 M/Cs are relatively common and work well on the '63s (that's what I have as see in the picture). You didn't mention brake hoses in your original post - damn sure change those too !!

There is also a foam seal at the firewall in addition to the boot (see picture)...

bluestreak63

Cool, thanks for the pic FTF!!

Yeah, the Raybestos unit looks like a nice unit and came with the foam seal as well. Funny, it's stamped Made in the USA on the unit, but indicates it's Made in Mexico on the box...

The shop manual makes reference to installing the pipe plug and tighten securely in one of the last steps in the MC assembly. I see no picture reference to this pipe plug. What is this pipe plug they speak of?