LAST EDITED ON Jul-10-19 AT 01:55 PM (EDT)
 
Session 10: July 9, 2019
The Joy of Plumbing

Not a super-exciting session today; in fact, there aren't even any photos, because most of what we were doing happened under the car. After completing the installation of the new brake booster/master cylinder assembly, and mounting the combination valve on the side of the latter, we got out the vehicle assembly manual to double-check how the original brake lines were installed.

What we found confirmed the investigation from earlier in the project, namely, the stock brake plumbing is a bit odd. The rear axle has two pipes for brake fluid, one running from the centerline to each wheel, with a T-fitting in the middle. That T is connected by a flex hose to the longest single brake pipe on the car, which runs from there up to the right front wheel. At that point there's another T, this one branching off a short pipe that connects to a flex hose and goes to that wheel, and a longer one that goes across the front subframe, under the engine bay, and to the left front wheel. At that point there is a third tee, which splits off another short pipe to the flex hose for that wheel, and one last longer pipe that goes up to the master cylinder on the firewall.

The new setup needs to be, oddly, both less and more complicated. More in that there are now going to be two separate hydraulic "circuits" (they're not really circuits, but it's a good enough metaphor), one for the front and one for the rear; less in that there won't need to be nearly as much junctioning to get it all going where we need it to go.

The new brake system includes a combination valve, which I mistakenly called a proportioning valve in earlier entries. It turns out that it contains a proportioning valve (that is, the valve that balances front and rear pressures so that the rear drums don't lock up when the front discs are getting enough pressure to work), but it's also a metering valve (which delays the activation of the front brakes for the tiny moment longer it takes the rears to start working, so that the car doesn't nosedive on braking).

Ours also has a pressure differential switch in it, which detects an imbalance in pressure between the two sides of the system and can illuminate a warning light on the dash if the car is so equipped. Ours isn't (they didn't have that light in 1962), so we don't have anything to connect that to unless we want to install one someplace in there.

The combination valve that came with our kit has three outputs on it: one for both rear brakes, and one for each front wheel. Given what we know about the way the car was plumbed from the factory, we figure this means the most efficient way to convert its brake plumbing into a two-zone system would be to:

- Either replace the two Ts at the front wheels with straight couplings, or plug the ports that used to lead to the front wheels, so that the original line goes directly from the rear axle to the rear-wheels port on the combination valve.

- Run new pipes from the front wheel flex hoses to the two front-wheel ports on the master cylinder. The pipe from the right front wheel can be routed alongside the original one that now goes to the back; the left front one just has to go up around the steering column and in.

While taking the existing system apart, we determined that the two long sections, the one across the front and the one from the right front to the rear, can probably be re-used, as can the T-fitting at the rear. The brake kit came with new hoses for the front wheels. We'll need to replace the two pipes connecting the rear T to the back wheels, the rear hose section, and possibly the two front Ts, unless we just cap the unused wheel ports on them.

While we're at it, we'll probably take the opportunity to switch the system from the old DOT 3 brake fluid, which is super-nasty and does bad things to paint finishes (modeling hobbyists sometimes use it as a paint stripper), to the newer DOT 5 standard, which is silicone-based, doesn't absorb water, and has a higher boiling point. DOT 5's only major drawback is that it can be aerated by the pump action in an anti-lock braking system, but that's not an issue in our application.

Our slowly growing to-be-acquired parts list also includes tie rods, an engine thermostat, a couple of bits and pieces for the interior, and—small but helpful details department—a new set of the little rubber bumpers that stop the spring-loaded fuel door from banging shut with a metal-on-metal clang when closed, the originals of which are long gone. Oh, and new wheel cylinders for the rear brakes, because they're 8 bucks apiece so why not, and probably rear axle bearings. Those wheel shafts sound a bit grindy when they turn.

I'm afraid it's gonna be a bit of a slog, this part of the project, and possibly not the most exciting part to write up or read about, but these are the deserts one must cross when restoring one of these cars...

--G.
-><-
Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Mod
Eyrie Productions, Unlimited http://www.eyrie-productions.com/
zgryphon at that email service Google has
Ceterum censeo Carthaginem esse delendam.

>DOT 5's only real drawback is that it doesn't like to be agitated,
>which makes it unhelpful in anti-lock brake systems, but that's not an
>issue in our application.
>

This still makes me sit up and go WAIT!!!! WHAT????
As in a fear that really low quality roads (of which there are more than a few in the greater los angeles area no matter WHAT the city and county want to claim) means someone like my mom might not be able to stop after crossing a really rough patch of road, even though she regularly throws me into the shoulder belt of standard 3 point restraints....

LAST EDITED ON Jul-10-19 AT 01:45 PM (EDT)
 
>>DOT 5's only real drawback is that it doesn't like to be agitated,
>>which makes it unhelpful in anti-lock brake systems, but that's not an
>>issue in our application.
>>
>
>This still makes me sit up and go WAIT!!!! WHAT????
>As in a fear that really low quality roads (of which there are more
>than a few in the greater los angeles area no matter WHAT the city and
>county want to claim) means someone like my mom might not be able to
>stop after crossing a really rough patch of road, even though she
>regularly throws me into the shoulder belt of standard 3 point
>restraints....

I don't think it's that kind of agitation. The problem, as I've seen it described, is that the rapid oscillation of the ABS pump can aerate DOT 5, and, well, there's a reason you've never heard of hydraulic foam. It would take a really rough road to duplicate that effect, I should think.

My original wording wasn't very clear, though, I should fix that.

--G.
-><-
Benjamin D. Hutchins, Co-Founder, Editor-in-Chief, & Forum Mod
Eyrie Productions, Unlimited http://www.eyrie-productions.com/
zgryphon at that email service Google has
Ceterum censeo Carthaginem esse delendam.