cant get good brake pedal

looking for input here fellas
im running a 4 drum setup, 40 fords up front 51 studebaker rear. new manual master cylinder under the floor and 10lb residual pressure valves front and rear. i bleed the brakes, no leaks, and i still have to pump up the pedal to get brakes. once i pump 5 or 6 times its a real good pedal, but a minute later and the pressures gone.
im looking for any inputs please.
thanks

 

might try adjusting the brakes themselves, that will usually cause this symptom if they are out of adjustment.

 

How much flex line did you use ?

 

Suggest having the system power bled---------you can hand bleed 'em 'till your face falls off and still not get all the air out, especially with an new system. It has worked for me several times.Also, choose your master cylinder wisely---- I have '40 Ford brakes on the front of my Model A with early Olds in the rear---- a '67 Mustang dual cylinder (for drum brakes w/o power) worked well.

 

did you bleed the master cylinder?

 

run the shoes out some. you are not making contact on the first pump. Happened on an old army truck I did.

 

what cheddar said....if you didn't bench bleed the master that'll most likely be the problem

Bill

 

Like they said try the shoe adjustment first and rebleed 'till you're sure there can't be any air. But I have had mastercylinders bleed preasure internally (even one brand new one) and spent a lot of time chasing other things only to replace the MC and have all the problems go away. So once you've tried everything else try replacing the MC. Good luck

 

40 front brakes can be tough to get adjusted right. It's more involved than cranking a star wheel that we are used to. This article explains the steps in their order. Starting with the lower adjusters in the right place goes a long way in getting them right. I print it out and take it to the garage everytime I adjust mine.

I'd check to see if there are any special steps needed to adjust the Stude rear brakes. I think my 53 Stude used the standard star wheel.

 

Sounds like they are not adjusted right to me too. I never had a problem getting the air out, unless there is a leak. When you pump the pedal it takes up the slack in the shoes and you get a good pedal. Then you stop and the spring pull the shoes back to where they are adjusted.

 

i did bench bleed the master cylinder, what is power bleeding?

 

power or pressure bleeding uses a special machine (which you can build without much money if you're clever or do a hamb search) which applies air pressure to the master cylinder, forcing the brake fluid thru the m/c, lines, and wheel cylinders.

triple-check the brake adjustment at each wheel, using apropriate instructions from an old shop manual or link as posted above, before resorting to pressure bleeding, though.

 

my buddy who works on planes showed me how they do planes, they reverse power bleed them from the cylinders to the master cylinder. works great. proper shoe adjustment as mentioned is also critical.

 

thanks for all the help. the problem was in adjusting the brakes. i got it figured out.
thanks again,
billy

 

Another thing to check that hasnt been mentioned here.
Make sure your brake rod going into the master cylinder isnt short.
What i mean here is that the pedal pushes freely before it starts to push the master cyl plunger. Usually there is an adjustment where you can lengthen the rod and take up this space.

 

Do you have alot of bends (or even just a few, but more than say 45 degrees)? Thats where I've always had a helluva time getting air bubbles away from. I had a 97 Explorer with a juice clutch and it was an unholy nightmare to get the air out of due to sharp bends. I've never tried forcing pressure thru the lines as a means of bleeding, but it sounds like a pretty good idea. I've had pretty good success with a Mity-Vac, not to mention from the point you buy one brake bleeding becomes a 1 man job. Fill the MC up, hook up the pump, and pull a good vacuum. Also really handy for putting fresh fluid in, I was AMAZED the first time I used it as to how much junk it sucked out, that alone was probably a great benefit. IIRC, you could probably use the pump to push fluid thru the lines similar to what the power bleeding sounds like, I'm pretty sure you can reverse it with no ill effects. It's a handy tool to have, any time you need to check vacuum anything it'll pay for itself (especially if you get an old car with alot of bells and whistles, all that shit is vacuum operated and a bitch to troubleshoot, I had a Cougar that was vacuum everything).