So I've been working on a 1970 car for a long time. I am trying to get it actually back on the street by end of summer (short build season here in Minnesota!).

I've finished the interior, and last Sunday I got the engine to run again for the first time in 8-9 years.

Working on the brakes next. Just to set the stage: I don't know ANYTHING I didn't learn in the process of trying to fix up this car. So knowledge is also skin-deep.

Ok, I checked out the brake fluid reservoirs. The front one is yellow and has some dried sediment on the bottom of the tank. The rear one is completely empty. So where did it go? Wheels off... turns out driver rear wheel doesn't turn. There is some kind of corrosion visible from the outside, on the drum. Is that where the. missing brake fluid went? Brake drum removed, the inside looks remarkably clean, but some corrosion or perhaps corrosion after-effect flakes in there.

What am I looking at? What should next steps be? Can I clean this up (neutralize it with something?) and put the cover on again, put in more dot3, and see what happens? If this is where the fluid went, why did it happen, and how do I prevent that from happening again? The emergency brake was removed from the car for something like that last 6 years, and it was up on wheel dollies that whole time. So wheels didn't turn. But also, I think that probably means the brake wasn't actually "on" during that period. (no tension, should have been off?).

What would people recommend? This is an early 1970 car, but it has so much unoriginal parts, I'm not trying to get it to perfect condition. So if some kind of brake swap would be better, I could look into that instead. Given my choice, I'd just try to get the original setup working. I'm not planning on swapping the engine for something more powerful any time soon.

@Warty I would clean everything off with a degreaser and pressure washer to see what is still useable. The rear brake cylinders can be rebuilt, the seals usually need replacing. Change out all the rubber brake lines. Remove and strip the brake master cylinder and replace the seals. Rebuild the front brake calipers with new seals. I'd then blow out the brake lines with an air hose then flush them with brake cleaner before starting to reassemble. You may want to check the brake proportioning valve in the rear and flush that out as well, same for the brake failure valve in the engine bay. I have just done all this on one of my cars and the brakes work great.

I'd also check the brake booster. Look for signs of leakage/paint peeling at the interface of the MC and booster and beneath. Take the bolts out of the MC and pull it forward to see if there's fluid in the booster. You can do it without removing the hydraulic lines.

Bear in mind, the seals for the early master cylinders can be difficult to source

I’m curious just looking at the pics, Crazy as it sounds it looks like saw dust material is on the inside and outside of the drum.

On 8/20/2026 at 6:18 PM, SpeedRoo said:

@Warty I would clean everything off with a degreaser and pressure washer to see what is still useable. The rear brake cylinders can be rebuilt, the seals usually need replacing. Change out all the rubber brake lines. Remove and strip the brake master cylinder and replace the seals. Rebuild the front brake calipers with new seals. I'd then blow out the brake lines with an air hose then flush them with brake cleaner before starting to reassemble. You may want to check the brake proportioning valve in the rear and flush that out as well, same for the brake failure valve in the engine bay. I have just done all this on one of my cars and the brakes work great.

Thanks for the action list. I'm working my way through it.

This video I found to be really helpful to see the details of how things come apart: https://www.youtube.com/watch?v=_nmI78Vqd1w&t=186s
Really useful.

I ordered what I think I'll need from Z car depot:

• 4 soft hoses

• shoes for rear brakes

• rebuild seals for rear wheel cylinders. Now that I'm in there, the rubber actually looks ok, but has to be at least 10 years old, and in one of them brake fluid leaked and sat there, so...

• 2x drum brake rebuild kit (springs, etc.). Not entirely sure the springs I have are bad, but figured while I'm in there...

• plugs for the hole in the drum (speaking of which... do other people have TWO holes filled with lead? I've only seen one hole with rubber plug, and one with lead plug. Mine has 2 right next to each other with lead, plus the other hole)

• master cylinder rebuild kit for Nabco.

I cleaned up the driver side drum. It turns out some PO painted it in a silver color. Must have been good paint... don't these things get super hot? Those radiator fins aren't there for looks. Anyway, the brake fluid got to it a bit. Did Brakleen and then steel wool and then sanding. Doesn't seem in bad shape really. But anybody see any red flags? (I don't really know).

I don't have the right 10 mm wrench to get the hoses off without damaging the nuts, so waiting on further disassembly of the rear brakes. I checked one of the front calipers, the pads looked almost new, and the pistons seemed fine. The front still has brake fluid, so pushing in one made the other one come out. Rubber I could touch felt ok and looked good. I think I may declare victory on that one anyway (once I replace the hose).

need to borrow an air compressor again to blow out the hard lines.

On 8/20/2026 at 7:14 PM, Zed Head said:

I'd also check the brake booster. Look for signs of leakage/paint peeling at the interface of the MC and booster and beneath. Take the bolts out of the MC and pull it forward to see if there's fluid in the booster. You can do it without removing the hydraulic lines.

I haven't had a chance to pull it forward, but I will later today. Is this the kind of paint peeling you were thinking of?

11 hours ago, Yarb said:

I’m curious just looking at the pics, Crazy as it sounds it looks like saw dust material is on the inside and outside of the drum.

I think that's just a photo resolution thing. I looked again at the photos I posted, and yeah, it does kind of look like sawdust. weird. but up close, it's crystalline. I think it reacted with the paint on the drum to create that effect? Other places it's just separate crystals of whatever is left after evaporation.

outside where it interacted with the silver paint it's weird and hairy and like something from an Alien movie. other places it looks like bread crumbs.

@Warty False economy not to replace all the rubber seals and hoses after sitting for 10 years. Pulling the front calipers and replacing seals only takes an hour, do it now while the system is drained of brake fluid. Also rebuild the master with new seals. Never trust what a PO has done, just assume it needs to be redone.

43 minutes ago, SpeedRoo said:

@Warty False economy not to replace all the rubber seals and hoses after sitting for 10 years. Pulling the front calipers and replacing seals only takes an hour, do it now while the system is drained of brake fluid. Also rebuild the master with new seals. Never trust what a PO has done, just assume it needs to be redone.

That makes sense. I'll order a couple of these:
https://zcardepot.com/products/front-brake-caliper-repair-rebuild-kit-240z-260z-280z?variant=19283631472753&currency=USD&utm_source=google&utm_medium=cpc&utm_campaign=google%2Bshopping&gad_source=1&gad_campaignid=17820837536&gbraid=0AAAAADgHqXsPjziYzQ0Jva87hSCR5eZKg&gclid=CjwKCAjwkaXUBhASEiwAZI3dsyqiQQ7tN8CISA-L3ODgvx3xeRHAcBYav7KajjEtGMhPAsJNnj3DahoCXo0QAvD_BwE

I haven't had a chance to look at either the brake check valve or the brake proportioning valve yet... what does "good" look like there?

@Warty most times they just need a good flush with brake cleaner. The rear proportioning valve is difficult to disassemble so just blow it out with air pressure then flush it with brake cleaner. Then put brake fluid in and seal with some caps until you reinstall it. The check valve comes apart pretty easily, again clean, flush and refill with brake fluid.

If you’re keen on replacing the master cylinder that’s up to you. Take your phone and take a pic of the bottom side of the m/c mounting points.