1940 plymouth p10 master brake and wheel cylinders

[ushp12]

I just replaced a leaking wheel cylinder.  When I went to bleed the brakes ( all new bleeder valves) I was able to get all, or most, of the air out.  I could not get the Brake Pedal to hold, it just keeps going to the floor.  I know that it is critical to keep the Master Cylinder full of fluid during the process and to close the Bleeder Valve before the hose is detached.  Anything else I should possibly repair or replace?

Thanks!

[Don Coatney]

What is your brake bleeding procedure? What wheel did you start with? Did you use a pressure bleeder or a helper? Etc?

[ushp12]

I followed the procedure stated in the Plymouth Shop Manual, dated 1940.  I put some clean brake fluid in a glass and ran a hose from the Bleeder Valve and submerged the other end in the jar with the clean fluid.  I started from the Rear Right Brake and opened the bleeder just enough to push out the Air, and stopped when there were no more bubbles.  I had a friend pump the brake pedal.  I tried to keep the Master Cylinder full during the whole process.  I then went to the Left side rear, and then the Right side front, and then the left side front.  I am using DOT 3 fluid.  If it was bleeding back into the master cylinder wouldn't there be a leak?  I do have 1 leaking bleeder valve on the Left Back , is there anything to use on the threads that would keep it from leaking?  Thanks for your help!  I hope you have more idea's on what the problem may be.

[Don Coatney]

Your procedure is correct. The threads should need no attention as the threads do not make the seal. The taper at the tip of the bleeder screw makes the seal.  If you have any leak in the system such as the leaky bleeder you mentioned that must be repaired before proceeding.

 

Did you bench bleed the master cylinder prior to installing it?

 

You might consider making an inexpensive power bleeder as it makes the job much easier. Instructions on how to make one using a hand pumped garden sprayer can be found all over the internet.

 

[ushp12]

Don,  I will change out the Bleeder Valve that leaks with another one.  I have not taken the Master Cylinder out of the car, so it hasn't been Bench Bled.  Could you help me with the correct procedure to bench bleed the MC.   Thanks again.    Dan

[jeffsunzeri]

To bench-bleed your single outlet master cylinder:

 

1. Remove the master cylinder from the vehicle, and place it in a vise to hold it securely. Make sure to protect the MC from damage from the vise.

2. At the outlet, install a short brake line and fitting as fitted on the vehicle, about 1-2 inches in length.

3. Attach a flexible hose to the short line from the cylinder outlet, using an optional hose clamp.

4. Fit the open end of the flexible hose into the reservoir of the master cylinder, filled with brake fluid, and keep it submerged. You may use a clothes pin or other soft clamp to keep the tube submerged.

5. Slowly but firmly operate the master cylinder using a suitable tool such as a ground-down screwdriver, or drift.

6. Observe the fluid returning to the reservoir from the tube looking for air bubbles.

7. The master cylinder is bled when no air bubbles can be seen returning to the reservoir while operating the cylinder.

 

The master cylinder is defective if it cannot be bled to a no-air-bubble condition on the bench.

Edited February 25, 2015 by jeffsunzeri

[Don Coatney]

This is a dual chamber MC but shows how to do it.

 

 

 

[ushp12]

Thanks Don!! The Photo's are helping a lot. It looks like it would be easier to take out the Front Floor Pan, and get the MC from the top? Maybe also to adjust the Pedal. My Clutch Pedal will not "spring" back to it's upright position. Spring maybe? Thanks

again, Dan

[ushp12]

Don, and others: I ended up putting kit's in all of the wheel cylinders, got them from NAPA. They did not have one for the LR cylinder. know where I can get one? Seems its a different bore size than the front.

This is probably a silly question, but in order to get the flexible brake line off I took off the cylinder and turned it to get it off. There must be an easier way. I have put the brakes bake together and forgot to twist the cylinder on to the flexible brake line, am I doomed to take it all apart again? Ohhh boy!

[David Strieb]

Try Hagens Auto Parts, Puyallup Wa.  hagensautoparts.com

 

  phone #1 253 854 7020

[Young Ed]

Don, and others: I ended up putting kit's in all of the wheel cylinders, got them from NAPA. They did not have one for the LR cylinder. know where I can get one? Seems its a different bore size than the front.

This is probably a silly question, but in order to get the flexible brake line off I took off the cylinder and turned it to get it off. There must be an easier way. I have put the brakes bake together and forgot to twist the cylinder on to the flexible brake line, am I doomed to take it all apart again? Ohhh boy!

The other end should spin with the fitting on the steel line. You need to loosen or remove that connection and then do the wheel cylinder end.

[Frank Elder]

Thank you Jeff, good description on a bench bleed.

[Daddyscar]

Found a way to move a bunch of Fluid through the system which is really what you need to do to get the air out of the lines. We tried bleeding the brake system the conventional way but the master cylinder does not move enough volume to get the air out. So, we hooked up a CLEAR 5' x 1 inch hose to a threaded barb that matched the fill port of the MC. Filled the hose with Dot 3 brake fluid. Cobbled together a way to attach air nozzle to the end of the hose with fluid in it. Turned air compressor down to about 5 psi. I applied pressure and my husband opened up the bleed port on right front wheel.Remember to keep an eye on the fluid level in the hose. You certainly don't want to go empty and start pushing air though again.  It took about 5 seconds of clear fluid running before bubbles started showing up. We had much difficulty because the wheel cylinder is below the line to the splitter on the left side of the car. If there is anyone out there scratching their heads and has a significant other complaining that their leg is cramping from pumping the darn brake pedal all day, I hope this helps.

 

Cheers!