Brake line size

Maintenance/Repairs
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1

I have a 1936 Dodge D2 sedan. Does anyone know what size brake lines I should use.

2

You don’t have any existing lines on the car to measure?

3

No

4

If you have the hydraulic parts this should be easy to figure out. The flare and the nut have to fit properly. I would guess 3/32 (common), but don’t take that as gospel. Take a wheel cylinder or master cylinder to an auto parts store and figure it out.

5

That’s what I used but for some reason I can’t get these brakes to work. I rebuilt all wheel cylinders and master cylinder. I used a pressure bleeder and also tried a vacuum bleeder. There are no leaks in the system. I even tried extending the plunger on the brake pedal that pushes in the master cylinder. Nothing makes these brakes move. The brake pedal will not get hard. Could the return springs be to tight. I was told they are correct for the year.
One thing I did notice was that when I took the wheel cylinders out to rebuild, for the 2nd time, it seem like there really wasnt much brake fluid in them. But when I bleed them I get a good flow thru them. I also have the shoes adjusted to specs.

6

One thing I did notice was that when I took the wheel cylinders out to rebuild, for the 2nd time, it seem like there really wasnt much brake fluid in them.

This seems key. I’m not familiar with the exact set up on this car but I’ve worked on a lot of older cars. One thing about older cars is they weren’t designed to be fool-proof (modern poke-yoke) and sometimes it’s possible to get orientation mixed up (BTDTBTTS). Is there any chance that the wheel cylinders can be mounted incorrectly such that the bleeders are mistakenly below centerline? The bleeders should be up high such that air must escape until the cylinder is full of fluid. If the mounting scheme allows for the cylinder to be mounted either way, and the bleeders are below centerline, that could explain why you get good fluid out but there’s still a boat load of air in them. Not meaning to impugn your skills here, just the only way I could think this would happen.

7

Have you plugged the outlet on the master cylinder and pumped the brake until the pedal was high and hard? You must do that first.

8

I agree with TT, more likely an installation or wrong part problem than a tubing size problem.

You say you rebuilt the wheel and master cylinders - are they in perfect shape? Usually they need to be replaced. Any rust/corrosion will negate the rebuild.

9

I agree with Rod Knox and TT:

  1. Check wheel cylinders orientation. And check operation with a hand pump like a “Mighty Vac.”

  2. YOU MUST FIRST BENCH BLEED THE MASTER CYLINDER as “Rod Knox” says

  3. Bleed brakes from rear to front. First with the wheel that is “most distant” by way of brake line length.

  4. Have lots of brake fluid on hand to remove any entrained air. In fact, you can put the thing on jack stands and put tubing on each bleeder and “gravity bleed” if you have the time. Just let the fluid “drip out” slowly to purge the air out.

  5. Make sure the M/C bore is not pitted and that the o-rings have not “slipped” or flipped-- causing fluid to “pump” within the bore but no other place.

Good luck,

Matt S.