Thread: Brake Help on 37 Chevy

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My 37 pickup has the master cylinder under the floor. I recently put in a completely new FatMan Fab Mustang II front end, new crossmember, all new disk brakes,everything front and rear. Replaced all the brake lines. We would have a pedal and then when turn the key on the pedal would go to the floor. So they checked all the lines for leaks, same with the calipers and such. Installed new residual valve. Installed new booster and new master cyclinder, I have brakes now but they are not very good. They will stop the vehicle but not in a hurry. The pedal also had about 2 inches cut from it before I purchased the vehicle and we relocated it for more throw but the brakes still arent that great. Any advice on how to get good brakes? I also wonder if i install a firewall mounted system if it would even fit with the steering and such being so tight now. Any help or suggestions is appreciated. Thanks.

Here's a troubleshooting page:

http://www.classicperform.com/TechBo...oubleshoot.htm

One concern is the alteration of the pedal length....the pedal ratio is
important to the system operation. However, it will not cause the pedal to go soft when the engine is started.....

One common problem is the length of the push rod between the booster and the master cylinder.....any old rod will not do it.....do a search on this site for previous posts about such a problem.

mike in tucson

Thanks for all the information and help. I have tried everything possible. I still think there is air in the lines. Last night if I push the pedal down it goes down almost to the floor before it will stop the car. If you pump the pedal 3 times quick the pedal only goes half way down and it will stop or slow it down. I talked to my buddy who installed it and he said we can should be able to return the booster and the mastercylinder. I was hoping to purchase a whole new setup that mounts to the firewall. Is there any brand that is good for this and is there any downside to having the setup at the firewall vs hidden under the floor? Lastly what do most trucks for these years use? Thanks a lot.

With the cylinder under the floor, you need a higher pressure residual pressure valve. The system will allow air back in with a normal valve.

you said you installed "a" new residual valve. you need 2 of them if you are using a duel master cylinder. with a booster, when you start the motor the paddle is suppose to go down some. if it don't you have a booster problem. how many valves do you have installed?

On my 37 chevy truck I have a dual master cylinder mounted under my floor like yours but I'm also running two residual valves and a booster. My pedal goes down about 3/4 to the floor but I have excellent brakes which stop my truck on a dime. I have disk brakes on the front and drums on the back.

I have a #2 in the front for disc brakes and drums in the rear with a #10. The only thing that is not new on the whole system is the proportioning valve, I'm wondering if the plunger is sticking or something. If I press the brakes I have to step on it all the way to the floor to hold the truck while at a light. If I pump them a few times quick the pedal goes about 3/4 down which makes me think there is still air in the lines. Supposedly he used a vacuum and said they did everything. I think it might be the proportioning valve. What do you think?

I have to agree with Denny. If your pedal is going down all the way and you have to pump them to get any brakes, it sure sounds like air in your system. I would bleed them again.

Yes I bet you have air in the system. I'd bleed them starting with the farthest one first and working back from there. It may and probably will take more than one time around. If you can locate a power bleeder that would help you a lot.

thanks a ton for that diagram. I'm going to try it like you show there. ill let u know if it works. Many thanks.