Master Cylinder Internals (power coating?)

[phaetn]

As I'm going about getting my engine rebuilt, I'm thinking of powder coating a few items that I had previously just spray-painted (cam covers, coolant elbow from head, rad fan bracket). I'm also thinking having the master cylinder power coated. Are there any internals that could be damaged by the baking process?

I'll take off the top nipples and seals, obviously, but are there any internal rubber seals? I'd assume so, but I cannot tell from this:
https://www.middlebartongarage.com/Prod ... linder/257
as parts #20, #21, and #22 are not identified in text.

This names them as seals:
https://www.spiderroadster.com/124brakemaster1.htm

Would they get too damaged by the baking/curing of the powder coating process? Also, what is the master cylinder made out of? I think it's likely a type of aluminum alloy but I'm not sure -- it is originally a light brown/tan colour (brass? copper?) but I know it rusts where it attaches to the firewall and discolours when brake fluid leaks onto it, so there must be some iron in there. I've cleaned them with a wire brush before but it keeps rusting.

Thanks and cheers,
phaetn

[18Fiatsandcounting]

I would definitely remove the "innards" from a master cylinder before powder coating the outside. The internals include 4 rubber seals, plungers, springs, and a few collars/washers. In addition to any seals for the two fluid supply lines.

I suppose it would work, although I would be careful to not get any of the coating in the threaded brake line ports or in the inner bore of the MC itself.

As for what it's made of? I've seen them in cast iron (perhaps original) but also aluminum in more recent versions. I know mine are cast iron as you can polish them up with a wire brush on a bench grinder and they are the color of a new (unseasoned) cast iron skillet, but then they develop a brownish patina as they age (i.e., rust). The weight is also different between iron and aluminum.

If you are seeing rusting from brake fluid, it's probably because brake fluid is pretty good at picking up water which then leads to rust. It shouldn't rusting in the inner bore of course. If it does, your brake fluid is bad.

-Bryan

[phaetn]

Thanks -- that's pretty much what I was thinking...

So remove the internals and yes -- as you point out -- protect any surfaces that mate to something else. They should be able to just mask it.

The leaks over the years have made a right mess of the paint in the engine bay. It's quite scary to just lift off paint with a plastic scraper that you can then pull off by hand. Ugh. My plan is to pull everything and paint the whole engine bay and hopefully address why it leaks. I think it's the seals on the top of the M/C since my garage is unheated and we get very cold winter temperatures. Emptying the brake fluid reservoir seems to help as it helps prevent the gravity fed fluid seeping out the seals.

Thanks and cheers,
phaetn

[18Fiatsandcounting]

The leaks over the years have made a right mess of the paint in the engine bay. It's quite scary to just lift off paint with a plastic scraper that you can then pull off by hand.

The good news is that you have several minutes to clean up spilled brake fluid before it begins to affect your paint, but I realize this doesn't help in your situation with an unnoticed slow leak. I have heard that DOT 4 brake fluid is a little less aggressive towards paint than is DOT 3, so switching to DOT 4 could buy you some time.

DOT 5 (silicone based) does not affect paint, but it's also not suitable for the brake seals in your Fiat, so that wouldn't work.

It's funny, I don't mind minor spills of gas, acetone, oil, coolant, etc on my paint (or epoxy-coated garage floor), but if I spill any brake fluid, I'm all over that stuff to get it cleaned up quickly...

-Bryan

[phaetn]

Yes, I'm the same way: A dribble of gas on the paint after a fill up doesn't bother me and just show's the car's aging masculinity. It coughs during check-ups, too. Brake fluid, though, I'm very quick to rinse off without wiping lest it mar the paint.

Any trick to getting the seals and nipples off? I don't want to force anything. I would assume it's just pry under the seal with a screw driver, or should I pull upright on the nipple (like a faucet's cartridge).

And then I assume, once I've drained it and disconnected it from the brake booster, to undo the big bolt at the front to pull out the internals...

I thought I had replaced the master cylinder when I replaced the brake booster in August 2017, but I went looking for the original and just cannot find it. I rarely, if ever, throw any old parts away so I guess maybe I just reused the old one. Funny though, as I thought I recalled hoping the fluid weeping would be cured with new seals on a new master cylinder and then was disappointed when it still leaked. Maybe it's the cold, or maybe I have too large a diameter threaded brake hose from the reservoir (I've got some German blue stuff, can't remember the brand) and it's not fluid leaking up, but fluid down the hose.

Thanks and cheers,
phaetn

[18Fiatsandcounting]

Any trick to getting the seals and nipples off? I don't want to force anything. I would assume it's just pry under the seal with a screw driver, or should I pull upright on the nipple (like a faucet's cartridge).

It sounds like you have the MC style where the plastic feed tube nipples are pressed into a round rubber "grommet" that goes into the feed holes of the MC. If that's the case, I carefully (evenly) pull the nipple straight up (perhaps with some very slight side-to-side movement), and then remove the rubber grommet.

As for that large nut on the end: They do come off, but it's almost always super tight and thus a real pain. Sometimes I just leave it alone and remove the innards from the brake booster end.

If your feeder hoses have too large an internal diameter, that could cause leakage. I just measured the internal diameter of some new hose that I bought from AutoRicambi for the early cars, and it measures 5.5 mm.

Finally, you probably know this, but regular fuel hose is not compatible with brake fluid, and it will start leaking over time. Brake fluid hose is a different rubber formulation.

-Bryan

[phaetn]

Thanks for that.

I think I may have discovered the problem, at least from looking at A/R's descriptions. I have the older style '66-77 vertical spouts that are designed for 4mm i.d. tubing but I have been using a German blue braided brake line hose that has a 6mm i.d. (originally for VWs) and clamping it. It previously had black tubes with appropriate bends, but also at 7mm i.d. -- those were there from the previous owner. I'm going from memory; I'll have to go out with a micrometer later and confirm.

If so, I'll order newer-style '77-85 elbowed spouts designed for 7mm i.d. and see if that cures the problem.

My '74 has dual bottles (I think earlier Spiders had only one non-separated reservoir so there was no dual circuit protection in case of leak) but I'm going with a new billeted aluminum reservoir with a 1/4" (6.3mm) barb. I'll clamp it down and it should be fine.

Cheers,
phaetn

[18Fiatsandcounting]

Sounds like you found the problem. And yes, my early cars use the AR brake fluid hose that says it's 4mm ID, although earlier I said mine measured as 5.5mm. Not sure why, other than perhaps the end is a little bit flared out from the cutting process.

I always view the angled inlets as better, as the sideways stress on the inlets that go straight up could cause them to, errr, break over time (pun intended).

-Bryan
PS: I think the only cars that had the single reservoir were 1968 and earlier. My '69 is dual reservoir.

[phaetn]

I think I got my measurements wrong. Went out yesterday and it looks like the nipple measures 3mm and that's pretty much what the i.d. of the hose was, too. I might order the angled ones anyway and see if they work. They might leak in a different way, I dunno.

I only mentioned the single reservoir as a friend (SpiderDan on these boards) has a '68 and believe they switched it over to two bottle for safety.

Cheers,
phaetn

[18Fiatsandcounting]

I only mentioned the single reservoir as a friend (SpiderDan on these boards) has a '68 and believe they switched it over to two bottle for safety.

That's my understanding. '68 was the first model year sold in the US, and there were a number of differences between that year and '69. Dual reservoir, torque tube vs. conventional driveshaft, etc.

Let us know how your brake feed line issue works out.

-Bryan