1940 brake issue....
 

My 1940 Tudor is a blast to drive, but the brakes are driving me crazy. The brakes are great....as long as you pump the pedal 1 time. The first press of the pedal is soft, but the second and every consecutive pump after that is rock solid. Everything is new including master cylinder, wheel cylinders, and lines....all stock. I've done quite a bit of reading on here about brake issues and found several people swearing by residual valves, so I installed them in the front and rear lines but not change. There are no leaks visable and no damp locations that I can see anywhere. The fluid level in the MC has not dropped. Last night I removed the sections that have the residual valves and retightened everything....just to make sure. I bled all the brakes again (went through another bottle of fluid just to make sure I got ALL the air out) and still have the same result.


I press on the pedal and its soft, but on the second press its firm. This happens every single time. I even counted to 5 and tried it again....same result....first pump is soft second and all subsequent are firm. If I wait 5 seconds the first pump is soft again.


Anyone have any suggestion on what to try next? Is this a sign of a bad MC or maybe I just didn't get it bench bled correctly? Any input is greatly appreciated......

Re: 1940 brake issue....
 

You might check brake adjustment. If the shoes have too much travel on first pump ,it will take another one to apply brakes.

John

Re: 1940 brake issue....
 

That is an excellent point. I'll check them tonight. Is there a recommendation for brake adjustment or do you just set them so they just don't drag? Thanks for the suggestion.

Re: 1940 brake issue....
 

Tighten so they drag and then back off just enough so there is minimal drag.

Mart.

Re: 1940 brake issue....
 

Sounds like you still may have air in the master cylinder or in one of the wheel cylinders to me!!! I would double check and make sure ALL the air is out of the system!!!! You didn't specify when you bled your brakes the first time after repairs IF the peddle got hard and stayed hard THEN got to where you have to pump them to get a firm peddle??? Sometimes the master cylinder can be a pain to get the all the air out.

Re: 1940 brake issue....
 

It could be the MC is mismatched to the wheel cylinders ,like to small .Ted

Re: 1940 brake issue....
 

Leaning towards improper adjustment of shoes and possible master cyl rod if changed to a new master cyl

Re: 1940 brake issue....
 

Those redial valves are good for dual MVP
One thing people do to bleed is to pinch the rubber hoses
That could be your problem

Re: 1940 brake issue....
 

Below I listed a link to an older thread by Paul Garrigan on adjusting '39-'42 Ford brakes.




Deleted the Link for adjusting brakes, as it was not needed.





.

Re: 1940 brake issue....
 

I just got done adjusting the brakes and although the rears seemed pretty close, the fronts were quite a bit off. I had to turn each adjuster almost 1/3 rotation before the drug slightly. I will take the car for a drive tomorrow or Thursday and see what it feels like, but with it on the lift it feels like the pedal is quite a bit more firm on the first push. Fingers crossed.....

I'm fairly certain I've got all the air out of the lines. I installed speed bleeders and pumped nearly a full bottle through the system....slow strokes and watching the hose closely. I know the MC can be tricky so that could be the culprit if it's still having issues. The MC is a new stock 40 Ford single pot so I'd think all the geometry is correct. Let's hope it was just br as ke adjustment.

Thanks everyone for the input. I appreciate the suggestions and advice.

Sent from my SM-G960U using Tapatalk

Re: 1940 brake issue....
 

Let us know how it turns out.

John

Re: 1940 brake issue....
 

Dont let the pedal go all the way to the floor when you bleed a single M/C . Speedbleeders are a great help.

Re: 1940 brake issue....
 

Sorry for the late response. I've driven the car a couple days and although the brakes are better, they still aren't great until I pump them 1 time.
I put the car on the lift last night and went over every connection on the brake system. Everything is BONE dry from the MC to the backing plates. I checked the brakes again and was able to adjust the passenger front a hair tighter. I'm going to drive it a few more times and I'll update again.
The brakes work and I can stop without pumping them, but it is a noticeable difference in pedal feel and brake pressure if I simply pump the pedal once whenever I need to use the brakes. Any suggestions on stuff to try? I can bleed them more but I've already gone through a full bottle of brake fluid the last time. Maybe I'm expecting too much from the old original system?
Thanks again for all the suggestions and info. I'll post again in a week or so......

Re: 1940 brake issue....
 

Well it's an improvement at least.

can you give us a clue as to the state of the linings, the diameter of the drums, the fit of the shoes to the drum, (have the shoes been "arced" to the drums), the adjustment procedure, did it include the eccentrics?. I have exactly the same setup on my 41 pickup, completely stock from one end to the other and that stops pretty well, so there must be something on your car that is not as good as on my pickup. I do not have any extra valving, just a new replacement master cylinder.

I arced the shoes to the drums using wet and dry inside the drum and rubbed the shoe back and forth. I adjusted them following a procedure that included the eccentrics. I swapped out an oversize drum and replaced it with one in better shape.

There are lots of things that could cause loss of pedal efficiency.

Mart.

Re: 1940 brake issue....
 

If everything is new you will need to adjust the brakes in 4 places for each wheel. Be sure to read and follow the instructions.

Charlie Stephens

Re: 1940 brake issue....
 

When bleeding the brakes best get the MC higher then WC jack up front or back as needed.
When I do mine I just crack the bleeder just enough to leak out and pump 10 times and when you see puddle on ground quick close bleeder. Keep MC full and do rest same way. Gravity does work that way. Make sure piston MC is all the way back. 1/8 play

Re: 1940 brake issue....
 

We have the opposite problem here with a 30 Chrysler it has a 3" master cylinder matched with a 1,1/4 wheel cylinders .its a very hard unresponsive pedal ,its about fluid displacement ,give us the cylinder sizes your new cylinder maybe to small ,did it have that problem with old M/C, Ted

Re: 1940 brake issue....
 

Thats what I was thinking .. Your linings might be undersize for the drum. If you lean on the pedal will it stop properly or ......aghh not! I chased this problem in my 56 Fairlane for ages , normal braking ok but stopping hard just didnt happen.. Someone previous had just put 'standard' linings in without checking the diameter of the drum. Here in Australia we go by 1st,2nd, 3rd oversize. When measured correctly these will fit the drum correctly and no need for arcing. Boy does it stop now!

Re: 1940 brake issue....
 

Get a new Master Cylinder.
Thank me later
Jim

Re: 1940 brake issue....
 

Adavis
Would you be using DOT 5 silicone fluid?
Bruce