40 brake dilemma

W

warren va

Senior Member
Wheel cyl. leaked[ DOT 3] and had to repaint backing plate. Decided to go with silicone fluid this time around. Installed new shoes, wheel cyls. and MC .
After bench bleeding and installing MC adj. brake pedal1/4 free play and push rod just almost touching.With help bled each wheel until no air or bubbles. Also NO PEDAL and after bleeding several more times and making sure to keep the MC topped off I still got no pedal. Blocked off the rear line and still no improvement. Clamped the front lines and pedal up and like a rock. Unclamped left front and pedal hardly moved . Reclamped L and removed R clamp.Pedal went to the floor. Pulled wheel and no sign of any leaks at wheel cyl. or anywhere on R side. Wished I had remembered to hold pressure on MC while wheel cyls were blocked.

Any suggestions. Warren
 
Also, you must flush the lines with alcohol, if I remember correctly. Too much pumping will create bubbles in the fluid and you will have to wait for them to disappear. Silicone fluid gives you a different pedal feel. That's what I experienced. On my latest project I used the synthetic and it hasn't bothered the paint.
 
If its a single master cylinder you shouldn't bench bled them. When installed put a brick or a piece of wood behind the pedal so it does not go to full travel, bleed as normal. Installing speed bleeders is well worth it too. Maybe just try holding the pedal halfway , see if you can block it there for half hour and gently try again?
 
I guess you have adjusted your brakes.
Quick check remove drum measure shoes 3-9 oclock.
They should be 1/8 less then drum .
Some times shose are to long should chamfer back both ends depth 1/8 back 1/2". You now can bring shoes out to 1/8 less then drum.
You should never clamp off rubber lines.
 
Thanks all for your suggestions.

Tried all this and still no pedal. Anyone else care to comment.


Thanks again
Warren
:(
 
crack each bleeder and pump till you see brake fluid on floor.
Then let gravity take on, make sure the MC is higher, use those jack stands.
 
If you did what I think you did, put a C clamp an the rubber hose to clamp off the line, I would suggest replacing the hose.

Charlie Stephens
 
The problem seems to be on the right front. Remove right drum and (since you have already clamped on the hoses) clamp all but right and have someone gradually press brake pedal. Watch the shoe movement (do not over do it). See if it's immediate or after some pedal travel. Sounds like too much shoe clearance or something to do with the wheel cyl.
 
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Help!! I have tried all the suggestions here on barn so far and still unable to get any pedal. Since the problem seemed to be in the right front replaced the new R & L front wheel cylinders and flex lines yesterday and no change. Removed the lines on M C and plugged outlets . Held pressure on pedal for 3 mins. and pedal like a rock, did not move. M. C. apparently is O K. Have bled the lines several times and no sign of air. What else can I do ? I am stumped.

Warren
 
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Did you pull the drums and check what I told you in post #4
If you are not all the way you get low pedal.
chamfer the ends of shoes if you cant put the shoes on, 1/8 less then ID of drum.
 
Thanks all.

Pulled the drum and checked the radius with brake shoe caliper . Adjusted brake shoes to 1/8 inch radius at 9and 3 o clock. That that leaves 1/16 shoe travel for back and front shoes. Also took the drum off R front and had my helper slowly apply brake . The shoes started moving immediately after barely pressing the pedal. I am using the Chinese mfg. M. C., shoes and wheel cylinders front and back. I noticed the tension springs in the front wheel cyls. are very weak compared to the old American made ones that I replaced.The pistons seem to bind and don't return as they should. Could this be a problem?

Thanks
Warren
 
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When you have the brakes adjusted pull the drum then measure.
See how close you are to drum size.
Center shoes even to 1/8 less then drum.
Now if you can't put drum back on the ends of shoes need chamfer.
Measure with piston back as far as they will return.
 
1/8" clearance is too much, brake shoes are still too far away from the drum at rest. I am also concerned about the rock hard pedal with the other brakes connected, sounds like they are adjusted too close. Suggest you start with wheel adjustment and get the shoes to slightly drag especially if you have replaced shoes or re-cut drums. The adjustment procedure below should get you close:
To adjust your brakes correctly, rotate the upper stops outward so the shoes contact the drum, and place a small amount of pressure on the brake pedal, now move to the lower adjustment bolts, loosen the lock nuts and rotate the adjuster tangs outward to feel the lower portion of the shoes just drag on the drum face. Upon a slight drag lock down the adjusted nuts and the hub should barely spin. Go back to the top anchor and rotate them one flat to center and the brakes should release and the drum spin free. Check the pedal stroke by pumping twice and relaxing, them push down with one even stroke, you should have a solid pedal within 1" of travel.
 
If you have it down to one side problem.
You could remove the shoes and get a c clamp hold piston in with clamp then try brakes. Pinched rubber lines will cause problems due the damage.
 
There have been other posts with similar problems ---the bleeder passage wasn't drilled to the top of the wheel cylinder creating an air pocket

You have narrowed the problem to 1 wheel, it's either trapped air or mechanical movement / binding ---take apart the wheel cylinder and look to see if the bleeder passage is at the top

I have bled wheel cylinders with broke bleeders by using a feeler gauge pushed past the cup
 
Most old Ford brakes are difficult to fully bleed without using a pressure bleeder, as mentioned above. Without one, it requires lots of fluid, even with DOT3. With DOT5, it gets expensive in a hurry. Never reuse fluid that is collected during bleeding, or you will contaminate the whole system.
 
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