I am building a 1930 Ford Roadster from the ground up and have a brake question. I have a speedway pedal and master cylinder kit (p/n 91631926) that is mounted in my frame, steel brake lines towards the rear with a wilwood proportioning valve and a 2 PSI residual valve then wilwood rear disc brakes. All steel lines and stainless steel braided hoses connecting to the calipers. Towards the front of the car all steel lines, 2PSI residual valve then disc drakes with stainless steel braided hoses connecting to the front disc brake calipers. There are no leaks and I have bled my brakes a few times with a mighty vac starting from the furthest away working towards the master cylinder. My issue is the first time I press the pedal down it is soft (like medium soft), every time after that I have amazing firm brake pedal. If I leave it sit for 15-20 minutes the first time I press it the pedal is medium soft but every time after it that is rock solid. Not having driven a car without power brakes in forever I am curious if this is normal behavior or thoughts on what else it could be?
Isnt it 10 pound valves for discs? 2 pounds for drums? Brake problems are such a big deal they need their own sub-forum. An index would be a big help
2 lb for disk, 10 lbs for drums.... Residual Valve Residual valves are used to maintain constant pressure on the brake system. For drum brakes, a 10 lb. residual valve is used to hold pressure against the springs in the drum. This allows the drum brake to engage more quickly and reduces pedal travel. For an under-the-floor master cylinder brake system, a 2 lb. residual valve is used for disc brakes to keep brake fluid from flowing back down into the master cylinder.
Air in the system is the problem, first: a mighty vac is ok if you don't have a leak, but even the slightest leak that will not even show up on the ground will always be taking in air every time you bleed the system. So the way to find the leak is with pressure. Clean all the lines good, have someone hold the pedal down and with a bright light, search for a wet spot, it may take awhile, you're looking for a very slight leak. good luck
Agreed, air is getting in somewhere , did you bench bleed master as it's possible it still has a tiny bit of air still in it, they can be a bastard to get out . An old tip is to wedge a piece of wood between pedal and steering wheel overnight so brakes are under pressure, this can cure it Sent from my iPhone using The H.A.M.B. mobile app
I have not been satisfied only using a mighty vac. Get it close with one, then get wife/girlfriend/mother/grandpa/neighbor kid to pump the pedal and you can finish the job.
The master cylinder really has to be fully stroked during bleeding to ensure purging all air from the bore, so make sure it can be full stroked before the pedal bottoms out on the floor or chassis. Once you have a decent pedal, stand on it for a short time to leak check. Cleaning all fittings and connections with isopropyl/denatured alcohol will help checking for leaks, and is very good for cleaning up brake fluid from parts, and hands.
I took everyones advice, cleaned all the fittings, engaged the brake pedal overnight to find a small puddle under the bad fitting near my residual valve. Have a new fitting on order then back at it. I do have another question, my master cylinder is lower than my calipers in the front and the back. Is there a better way to bleed when this is the case? Thanks for the help!
Glad to hear you found the leak I would get it fixed and then just go round and bleed longest line first and then the next shortest and so on. It's worth mentioning the residuals should be mounted as close to the master as you can get them ideally Sent from my iPhone using The H.A.M.B. mobile app
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