I have been chasing a brake issue. All new brake line, hard and soft lines, new wilwoood master cylinder along with 10LB valves since I am running 37 wide five on front and back. I have bled the brakes no air in them coming out pure fluid the pedal will get hard then I come back a few minutes later and pedal goes right to the floor. If I pump the pedal a few times it will get hard again. Anyone have any suggestion on what would resolve this? Thanks
Sounds like to me you need to adjust shoes out closer to drums. What's probably happening is your shoes are far away from drums and as you pump your pedal your expanding the wheel cylinders until you make complete contact with the drums and a good full solid pedal. When you let off the wheel cylinders slowly collapse due to brake shoe springs pulling the shoes back in then you have a low soft pedal again. ...
Probably what he said, if that doesn't fix it, block off fronts and retry, then block off rears and retry. IF nothing helps, it could be the M/C, but try the other stuff before you condemn.
You could also have an issue with the residual pressure valves. I used a pair of Wilwood RPV's and always fought with a low and soft pedal. Finally tore it apart and the RPV for the front brakes was bad from the factory. Installed new ones (not Wilwood) and the problem went away...
Maybe a bypassing master? Some are easy to ferret out and will repeat their behavior. Others are as sly as a fox.
Someone has to say it: 37 brakes were cable operated. No fluid to be spongy. Do you know what you really have?
Would you like me to refer to them as 39 brakes? 37-39 hubs are the same and I have 1937 wide 5 hubs with 39 backing plate since 39-48 are all the same. So to answer your question yes I do know what I have
As has been said try adjusting your brakes tighter. Also, I assume since they are 37 wide 5’s you’re using 39 and up Lockheed brakes? They can be finicky to adjust to make sure the whole shoe is making contact.
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