Ok - now I am stumped

[Guest MelJan]

I have finally tried everything I know and am still stumped. I am trying to rebuild a master cylinder on a 38 Dodge Business Coupe. The original had no real pressure at all, with the pedal going right to the floor without any effect. I already rebuilt the wheel cylinders and therefore assumed the master was the problem.

I picked up a rebuild kit, but the only one available was for a '36 and not a '38. All the parts looked identical with the exception of the length of the piston. So all the new parts went in, and the old piston was put back as well. I bench bled the master, reinstalled it, then pressure bled the lines, but I still dont get any pressure. I looked at the '38 repair manual and followed the diagram - in the even I screwed up and put things back in a wrong order - and still nothing.

So, now I am stumped. Does anybody have any suggestions to help the mechanically challanged? I might have to brake down (no puns intended), and take it into the local shop, but what fun is that? I thought I would ask here first.

Thanks for any advice.

[Guest John1918]

The brake fluid must be going somewhere and returning when you release the brake unless it's all over the floor! Has something gone wrong with the brake shoe adjustment in one wheel or with a wheel cylinder perhaps. Presumably the master cylinder pumped ok on the bench? Also check the little bypass hole in the bottom of the master cylinder just in front of where the piston sits is not blocked. A longer piston might cover this hole and prevent it operating correctly. I'm not familiar with the "38 car but I guess they have the same bypass as others. John

Edited July 3, 2009 by John1918
additional info (see edit history)

[keiser31]

All I can add is to be certain to ALWAYS adjust shoes correctly prior to bleeding. I agree with John1918.

[Guest MelJan]

Thanks for the tips. I took the master into a local shop in Vancouer (DV Aldous), who have been specializing in brakes since Moses was just a young boy. They took apart my master and changed the piston etc and gave it a clean bill of health (at no cost). They also talked to me about adjusting the brakes and were most helpful in walking me through this. Has anyone adjusted both the top and bottom of the shoe (where the pin is that the shoe anchors into)? I did not see the lower in the manual, but it was described to me how to do a lower adjustment along with the upper. Does this make sense???:confused:

[keiser31]

You really don't want to mess with the lower anchor bolts. You really should try to get a shop manual for the car. It explains everything about how to adjust the brakes.

[Guest simplyconnected]

Start at the M/C. I know you bench bled, but that doesn't mean it will push fluid into your lines. Remove the flare fitting and have someone push the brake pedal while you put your finger over the output hole. Do that until you feel a good amount of brake fluid spritz out, then replace the line.

Go to your NEAREST bleeder valve and do the same finger routine until fluid comes out. Follow with the subsequent bleeder valves.

I had the same thing happen to me and couldn't understand why no pressure at the cylinders. It's there now! All my parts are brand new including hoses, so I knew none of the components were faulty. You are used to dealing with a system that's been working. New (empty) components act differently at first.

[JACK M]

All my parts are brand new including hoses, so I knew none of the components were faulty.

I NEVER would presume that new parts could not be at fault.

[keiser31]

Big DITTO on that one.

[Guest MelJan]

Thanks for all the advice. I do have a shop manual and it does not say anything about adjusting the lower pins when adjusting the brakes - hence my question. It did not seem to make sense to me to do that - not to say that everything has to make sense to me, but that one didn't. I will try the tip from Simplyconnected because it does make intuitive sense to me.

[Guest simplyconnected]

All my parts are brand new including hoses, so I knew none of the components were faulty.

I NEVER would presume that new parts could not be at fault.

Big DITTO on that one.

Hey guys, I check my new parts. That's how I KNEW my parts weren't faulty. I've been around long enough to never assume anything.

I know how it feels after bench-bleeding a brand new dual M/C; you connect to brand new brake lines and hoses, and the damn thing won't bleed because there is NO pressure. That's when you fall back and punt. After doing the M/C spritz, I was never so happy to see DOT-3 come out of the first bleeder screw. After the first, all the rest fell in line.

After a week, I'm going to bleed the lines the way I always have, just to make sure no filings are in there from doing all those double flares, and to be absolutely sure I have fresh DOT-3 from a new container.

I hope you find the same thing I did. When the lines are totally empty, and you are using new components, they don't like to bleed. That's why the factory evacuates before filling. If the system doesn't sustain a vaccuum, they don't fill.

Dave Dare

[hwellens]

Page 28 of the 1938 Dodge shop manual shows the lower adjusting cams. These are the pins that were referred to. There are 4 adjustments to these brakes. The lower ones have to be correct or the brake shoes will not be concentric.

[keiser31]

Oh....the brakes that I was mentioning earlier are different. I was talking 1931 brakes. They are different. I guess that you do actually adjust the lower pins on the '38s. Sorry for the wrong information.

[Rusty_OToole]

There is a major adjustment that centers the brake shoes in the drums and a minor adjustment to take up wear.

If you have not replaced the brake shoes the minor adjustment is all you should need.

[hwellens]

If you removed the cams and not just the C-clips to get the shoes off, you need a major adjustment.

[Guest MelJan]

I did replace the shoes, but only removed the clips to get them off. Therefore no adjustment / alteration to the pins was made.

[Reg Evans]

If you have replaced the shoes you will need to adjust both the major and minor adjusters. It is important to get the shoes centered in the drum for even wear and the best breaking. An ammco model 1750 brake adjusting tool is the ticket for adjusting the shoes correctly the first time.

[Guest alex_houston]

When I had that problem it was the push rod length from the pedal to the master cylender was wrong. New parts made adjustments all wrong. Adjusted rod/pedal and finally pushing brake pedal was actaully pushing on the master cyl.