brake question

69mach351 · 07-10-2002, 07:56 PM

I have not figured out what is wrong with my brakes. I have it narrowed down pretty good. My question is; why does my brake pedal only get stiff if I pump it five times or more (car off). If I stop pumping it for two seconds the pedal will go to the ground again. Brakes and Master cylinder are bled (no leaks). Master Cylinder, booster and rear cylinders are new. The only possible thing that I can think of is that the star adjusters don't work, or that the front brake pistons are worn down and don't work effectively. Are these the only possible problems? I would be extremely grateful if anyone can give me any more information.

Clark Rodgers · 07-11-2002, 11:21 AM

I don't know if I have a magic cure but I will throw in my two cents. The (star) self adjuster on your rear brakes should be turned out so that the drums fit snug over the shoes. From your discription I am assuming you have disc on the front, but if not just use the small slot on the brake backing plate to adjust the self adjusters on the front drums so that you just hear the shoes rubbing. This will take the self adjuster issue out of the picture.

If this is good than you sound like you have air in the system. I know you said that you bleed the brakes but did you bleed the master cylinder first before installing it? Alot of people say they will just bleed it on the car but this will take over a 1/2 dozen times before you can get this air out. And have you got the right master cylinder? The disc one will have a large and small reservoir and the all-drum will have the same size reservoirs.

PKRWUD · 07-11-2002, 11:36 AM

My first reaction is also to sak if you bench bled the master (if it was replaced). If it wasn't replaced, it may need to be. The easiest way to find out is to remove the brake lines, and insert plugs into the openings on the master. Then press and hold the brake pedal. If it fades, the master cylinder is bad, and must be replaced.

If the master is new, was bench bled, and the rest of the system was bled correctly, the last possibility is a damaged hose. Check the hoses from the frame to the front brakes. Inspect them while an assistant pumps the brakes. What you're looking for is a balooning effect somewhere in the hose. If you find this at any point on either hose, replace the hose.

Take care,
-Chris

69mach351 · 07-14-2002, 05:09 PM

Thank you for the information. The master cylinder was bled, no air in the lines, no leaks, and no pedal. I will check for balooning brake hoses (why can't I find this kind of information in books?) and see what happens. Thanks, David

Jeff65 · 07-17-2002, 04:19 PM

Just about everything's covered but I think its most likely have a bad master cylinder. Just because its new doesn't mean its good or right. Rebuilt master cylinders are not always rebuilt well or tossed out when over specifications (over honed or over bored).

Try buying a new Wagner MC from O'Reillys or other auto parts stores that carry them.

Make sure you have the right MC with no substitutions. Drum brake MC's often have residual valves built in that disc brakes don't need. Getting the wrong model or connecting the wrong section of dual MC's to the lines can result in wierd operation.

Rev · 07-19-2002, 06:19 PM

My opinion is it's almost certainly a bad MC, unless there are obvious leaks at the wheels or lines.

Rev

69mach351 · 08-12-2002, 10:10 PM

I finnaly fixed my brakes. The problem was that when I put the new master cylinder in the rod from the booster to master cylinder was too short. I kept loosening the skrew until finnaly a had a firm pedal. The directions said to measure a 1/16th in. of putty and put it in there and see that it barely touches the master cylinder ( barely presses down on the puddy). I ended up just making the rod longer and longer until I got a pedal. Not the best approach but I won't have to mess with it again.
The brake problem first started with a leak in the line. I fixed the leak, and ended up creating new ones. I replaced the master cylinder on an assumption and that is where the above new brake problem began. It seems that fixing a problem sometimes creates new problems. The big lesson; don't try to flare the lines yourself. Thanks all for your help. My car is on the road finally ( for now). David B.

07-10-2002, 07:56 PM	#1
69mach351 Registered Member Join Date: Jan 2002 Location: California- Hollister Posts: 14	brake question I have not figured out what is wrong with my brakes. I have it narrowed down pretty good. My question is; why does my brake pedal only get stiff if I pump it five times or more (car off). If I stop pumping it for two seconds the pedal will go to the ground again. Brakes and Master cylinder are bled (no leaks). Master Cylinder, booster and rear cylinders are new. The only possible thing that I can think of is that the star adjusters don't work, or that the front brake pistons are worn down and don't work effectively. Are these the only possible problems? I would be extremely grateful if anyone can give me any more information.

07-11-2002, 11:21 AM	#2
Clark Rodgers Registered Member Join Date: May 1999 Location: Rowlett,Texas Posts: 306	I don't know if I have a magic cure but I will throw in my two cents. The (star) self adjuster on your rear brakes should be turned out so that the drums fit snug over the shoes. From your discription I am assuming you have disc on the front, but if not just use the small slot on the brake backing plate to adjust the self adjusters on the front drums so that you just hear the shoes rubbing. This will take the self adjuster issue out of the picture. If this is good than you sound like you have air in the system. I know you said that you bleed the brakes but did you bleed the master cylinder first before installing it? Alot of people say they will just bleed it on the car but this will take over a 1/2 dozen times before you can get this air out. And have you got the right master cylinder? The disc one will have a large and small reservoir and the all-drum will have the same size reservoirs. __________________ 69 393W Sportsroof deluxe

07-11-2002, 11:36 AM	#3
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	My first reaction is also to sak if you bench bled the master (if it was replaced). If it wasn't replaced, it may need to be. The easiest way to find out is to remove the brake lines, and insert plugs into the openings on the master. Then press and hold the brake pedal. If it fades, the master cylinder is bad, and must be replaced. If the master is new, was bench bled, and the rest of the system was bled correctly, the last possibility is a damaged hose. Check the hoses from the frame to the front brakes. Inspect them while an assistant pumps the brakes. What you're looking for is a balooning effect somewhere in the hose. If you find this at any point on either hose, replace the hose. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

07-19-2002, 06:19 PM	#6
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	My opinion is it's almost certainly a bad MC, unless there are obvious leaks at the wheels or lines. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe

08-12-2002, 10:10 PM	#7
69mach351 Registered Member Join Date: Jan 2002 Location: California- Hollister Posts: 14	there is a conclusion! I finnaly fixed my brakes. The problem was that when I put the new master cylinder in the rod from the booster to master cylinder was too short. I kept loosening the skrew until finnaly a had a firm pedal. The directions said to measure a 1/16th in. of putty and put it in there and see that it barely touches the master cylinder ( barely presses down on the puddy). I ended up just making the rod longer and longer until I got a pedal. Not the best approach but I won't have to mess with it again. The brake problem first started with a leak in the line. I fixed the leak, and ended up creating new ones. I replaced the master cylinder on an assumption and that is where the above new brake problem began. It seems that fixing a problem sometimes creates new problems. The big lesson; don't try to flare the lines yourself. Thanks all for your help. My car is on the road finally ( for now). David B.

07-14-2002, 05:09 PM	#4
69mach351 Registered Member Join Date: Jan 2002 Location: California- Hollister Posts: 14	Thank you for the information. The master cylinder was bled, no air in the lines, no leaks, and no pedal. I will check for balooning brake hoses (why can't I find this kind of information in books?) and see what happens. Thanks, David

07-17-2002, 04:19 PM	#5
Jeff65 Registered Member Join Date: Jul 2002 Location: Oklahoma City Posts: 208	Just about everything's covered but I think its most likely have a bad master cylinder. Just because its new doesn't mean its good or right. Rebuilt master cylinders are not always rebuilt well or tossed out when over specifications (over honed or over bored). Try buying a new Wagner MC from O'Reillys or other auto parts stores that carry them. Make sure you have the right MC with no substitutions. Drum brake MC's often have residual valves built in that disc brakes don't need. Getting the wrong model or connecting the wrong section of dual MC's to the lines can result in wierd operation.

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