Thread: Brakes

Tweet

I'm going to try this website one more time for help. I have a 38 Chevy 2 dr sedan. I have replaced the master cylinder, 7"booster, combination valve,all the lines with 5/16 steel. I still have really bad brakes. When you push the pedal down it will move about 2 inches then it's like standing on a brick. The brakes have been bled a couple of times at first there was no pedal at all . Now the pedal is up but brakes just don't want to stop. Someone said it might be the rear wheel cylinders? Then someone said maybe not enough vaccum. I'm afraid in a panic stop situation it will not stop. Can anyone help please? Thanks!

Sounds like you need someone who knows brakes to diagnose your system. The reason you may not be getting responses is that it's all guess work when you have the hardware in front of you and we don't.

Here's some basics to review to help you do a better job of diagnosis; http://www.ecihotrodbrakes.com/brake_facts.html

If you lines really are 5/16 then it's possible you don't have a large enough master cylinder since normal brake lines are 3/16.
Could be your pedal ratio is bad. Could be you're not getting full flow in the system. Could be lots of things.

Originally posted by Steel Warrior
I'm going to try this website one more time for help. I have a 38 Chevy 2 dr sedan. I have replaced the master cylinder, 7"booster, combination valve,all the lines with 5/16 steel. I still have really bad brakes. When you push the pedal down it will move about 2 inches then it's like standing on a brick. The brakes have been bled a couple of times at first there was no pedal at all . Now the pedal is up but brakes just don't want to stop. Someone said it might be the rear wheel cylinders? Then someone said maybe not enough vaccum. I'm afraid in a panic stop situation it will not stop. Can anyone help please? Thanks!

i dont know what you have or haven't done to your car, but on a reg. car with power brakes and you had this problem it would be either no vac. or not enough vac. to work the booster or a bad booster. you need to check the vac. at the booster and you'll need about 13-14"+. its sounds like you have no vac. at all there. pull the line off of the booster, if you have vac. put it back on with someone else pushing on the pedal and see if the pedal moves, if it dont the the booster is no good.

Sorry, 5/16 was a slip of the finger error. I will check the vaccum then try to measure the pedal to see if the ratio is off. The only problem is there is no more adj there. The pedal is moved as far as it can go. Unless I more the whole set-up forward somehow. This has been driving me crazy. I have never had so many problems with brakes before on anything. Thanks very much for getting back!

Originally posted by Steel Warrior
Sorry, 5/16 was a slip of the finger error. I will check the vaccum then try to measure the pedal to see if the ratio is off. The only problem is there is no more adj there. The pedal is moved as far as it can go. Unless I more the whole set-up forward somehow. This has been driving me crazy. I have never had so many problems with brakes before on anything. Thanks very much for getting back!

You don't need to move the pedal, anytime you plug or unplug vac. to a booster it should pull the pedal down some. It will move (or suck in) the diaphragm in the booster. you should feel a dif. in the pedal.

Sounds like bad booster! The push-rod for the booster is oftentimes prone to damage during installation, breaking the diaphragm. Also might try pulling vacuum hose off motor and then pulling check-valve out of booster to see if it's holding stored vacuum in the booster. Also need to check adjustable push rod from booster diaphragm to master for correct adjustment.
Most folks don't want to be guessing about somebody else's brake problem. You're probably only going to be given advice for not-in-motion testing.....Good luck!

I meant, if I had to move the pedal for the proper ratio. I would have to move the whole assembly forward since it has the pedal arm against the floor now. The rod can not be adjusted at all. now. I tried two different boosters both new and with the same results also two master cylinders. I will just have to keep checking things. I understand about the non motion checks. Every little thing helps when trying to figure this type of problem out. I know it's probably something simple and right in front of me. THANKS!

What is your pedal ratio, and how much vacuum is your engine making???

We are looking into the pedal ratio now. Trying to mearuse it on the car. Then we will check vaccum and pedal throw. We are looking at trying to extend the pedal travel and see if that does anything. Thanks for the help!!

Are the wheel cylinders running out of stroke before the shoes contact the drums? Some brake setups have positive stops so the wheel cylinders can't pop apart. If the brakes aren't set tight enough, you can get a hard pedal with no braking.

The wheel cylinders seem to be working OK. The travel seems to be fine. But, I plan to replace them anyway. Since they are only a couple of dollars and they seem to have been in there a long time. I'm willing to try anything at this point. Thanks for the help!