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Soft Brake Pedal to Floor on 4 Wheel Drum Manual Brake System - 69 Charger

robl72

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I have a 69 Charger 440 Auto Trans R/T Restored in a stock configuration. It has the original 4 wheel 11" HD drums with stock Manual master cylinder setup. This winter I was swapping out shoes front and back. Once complete I found that my previously hard pedal was now very soft and extends almost to the floor before getting hard. At no time was the fluid system opened and I adjusted brake shoes to the proper drag when completed. The Master Cylinder is fairly new and was working fine prior. One difference from the start was that I changed the rear drums from smooth to finned. The new finned drums are NOS Chrysler 11 x 2 1/2. Old drums were original Chrysler non finned 11 x 2 !/2 with springs.

The only other thing I can think of that could have had an affect was the Brake pedal being depressed when the rear shoes were not on yet causing the wheel cylinders in the rear to extend out. They did not over extend to the point where fluid was lost or any air introduced to the system that I know of. In an attempt to fix the soft pedal I bleed the front and rear with no significant difference. M/C Fluid level was checked and was full

My questions are;

1. Could depressing the pedal with no rear shoes on have done something to the distribution block to now cause a soft pedal?

2. Could Depressing the pedal with no rear shoes on have cause air to get into the M/C? I personally don't think so but who knows.

Any thoughts on this issue please let me know. Thank you!
 
One guy on a forum gave me a suggestion that helps narrow down where a problem lies....He suggested to disconnect the lines at the master cylinder and put some sort of plug in each port to block them off....then press the pedal. If it is suddenly firm like it should be, your problem is not the master cylinder, it is somewhere downstream from it. If the pedal is still soft, the master cylinder is likely the problem.
 
One guy on a forum gave me a suggestion that helps narrow down where a problem lies....He suggested to disconnect the lines at the master cylinder and put some sort of plug in each port to block them off....then press the pedal. If it is suddenly firm like it should be, your problem is not the master cylinder, it is somewhere downstream from it. If the pedal is still soft, the master cylinder is likely the problem.

One guy on a forum gave me a suggestion that helps narrow down where a problem lies....He suggested to disconnect the lines at the master cylinder and put some sort of plug in each port to block them off....then press the pedal. If it is suddenly firm like it should be, your problem is not the master cylinder, it is somewhere downstream from it. If the pedal is still soft, the master cylinder is likely the problem.
That makes a lot of sense.. Just cant figure how my MC could have a problem now. It was fine before.
 
Are the shoes adjusted so the drum drags a bit when you rotate them by hand?
 
Here is what I would do.
1-Back off emergency brake.
2-Re-adjust all 4 wheels.
3-Adjust emergency brake.
4-Bleed all 4 wheels.
 
Are the shoes adjusted so the drum drags a bit when you rotate them by hand?
Well I read your write up again and apparently they were. Maybe try driving it a bit to bed them and then see if you can get more adjustment?
 
Here is what I would do.
1-Back off emergency brake.
2-Re-adjust all 4 wheels.
3-Adjust emergency brake.
4-Bleed all 4 wheels.
Hi thanks, I like your plan … that was my intisl thought…

Why do you say back off the E Brack though? Also could it hurt cracking the MC lines to blead it off some there as well? I assume the distribution block has nothing to do with this problem?
 
Hi thanks, I like your plan … that was my intisl thought…

Why do you say back off the E Brack though? Also could it hurt cracking the MC lines to blead it off some there as well? I assume the distribution block has nothing to do with this problem?
The correct way to properly adjust the rear brakes in to make sure the emergency brake is fully backed off. Then the service brake is adjusted. Then the emergency brake is adjusted. Not having it adjusted in the correct sequence will have improper pedal feel and operation. You can bleed it off in other areas. I doubt you will have any benefits. I would just do all 4 wheels and bleed them well.
 
Ok I
The correct way to properly adjust the rear brakes in to make sure the emergency brake is fully backed off. Then the service brake is adjusted. Then the emergency brake is adjusted. Not having it adjusted in the correct sequence will have improper pedal feel and operation. You can bleed it off in other areas. I doubt you will have any benefits. I would just do all 4 wheels and bleed them well.


Ok what you said makes a lot of sense..I will do exactly as you mentioned… in your experience though would The distribution block have any affect on my problem? I’m really curious as to the symptoms of a bad one.. I can’t find any information on the symptoms once one goes bad.
Thank you!
 
I’m not saying this is the problem, but when you depress the brake pedal all the way to the floor you move the piston past the point that it has been operating in.
If there’s rust or pitting there it may damage the seal.
This is just a theory I have and why I try to avoid pressing the pedal all the way down during bleeding.

I have had a couple of incidents over the years that I’ve had to replace the mc after doing other brake work.
 
Ok I



Ok what you said makes a lot of sense..I will do exactly as you mentioned… in your experience though would The distribution block have any affect on my problem? I’m really curious as to the symptoms of a bad one.. I can’t find any information on the symptoms once one goes bad.
Thank you!
I have never seen a valve affect the height of the pedal or lack of pedal. Soft low spongy pedal is mostly due to travel or air. Master can play games. Most commonly is you have pedal and then the pedal slowly drops down because the master is bypassing internally. Just try the 4 steps I described.
 
I’m not saying this is the problem, but when you depress the brake pedal all the way to the floor you move the piston past the point that it has been operating in.
If there’s rust or pitting there it may damage the seal.
This is just a theory I have and why I try to avoid pressing the pedal all the way down during bleeding.

I have had a couple of incidents over the years that I’ve had to replace the mc after doing other brake work.
Now that I think about it more,You should check the FSM. IIRC there are two pistons and if line pressure is lost they will move together and can get stuck.
I might be full of crap, like I said check the FSM.
 
Here is what I would do.
1-Back off emergency brake.
2-Re-adjust all 4 wheels.
3-Adjust emergency brake.
4-Bleed all 4 wheels.
4a- Start bleeding furthest from the master cylinder first. RR, LR, RF, LF. A spongy pedal is usually air in the system. Does the pedal improve if you pump it a couple times? If so, it's air.
 
It Improves a little when I pump. The thing that gets me is that it was fine prior to the brake shoe swap. And I did not break into the hydraulic system or introduce air into it that I know of. I am going to try to re adjust and bleed as described. Just have to find time this weekend to do it.
 
This is funny…I’m going through the EXACT problem you are. ‘68 Super Bee, manual drums.

Everything was fine when I parked it in the fall, except the front drums were getting warped and the front shoes were showing heat cracks on the friction surface…I bought the same, but must be the newer model of the 11x3” drums (raybestos) and centric shoes. Never opened the system, just replaced the shoes and drums and followed the FSM to the letter, although the ‘68 one doesn’t mention the HD brake adjustment procedure so I tightened the adjuster to just a little drag. All ready to take it for a spin and just like the CW McCall song….stepping on a plum. My formerly rock solid pedal was just mush…I never touched the rears at all. Tried diff shoes and a new pair of drums again.. Same. Flushed the fluid at each corner and bled all 4 starting w the pass rear. SAME. I’m at a loss here too. I just bought a new master cylinder to try that next. No clue what’s going on.

**If anyone has any tips on bleeding and installing a manual master cylinder, I’m all ears**. The new one doesn’t come with a pushrod so I guess they’re re usable?
 
This is funny…I’m going through the EXACT problem you are. ‘68 Super Bee, manual drums.

Everything was fine when I parked it in the fall, except the front drums were getting warped and the front shoes were showing heat cracks on the friction surface…I bought the same, but must be the newer model of the 11x3” drums (raybestos) and centric shoes. Never opened the system, just replaced the shoes and drums and followed the FSM to the letter, although the ‘68 one doesn’t mention the HD brake adjustment procedure so I tightened the adjuster to just a little drag. All ready to take it for a spin and just like the CW McCall song….stepping on a plum. My formerly rock solid pedal was just mush…I never touched the rears at all. Tried diff shoes and a new pair of drums again.. Same. Flushed the fluid at each corner and bled all 4 starting w the pass rear. SAME. I’m at a loss here too. I just bought a new master cylinder to try that next. No clue what’s going on.

**If anyone has any tips on bleeding and installing a manual master cylinder, I’m all ears**. The new one doesn’t come with a pushrod so I guess they’re re usable?
Hey sorry I just read this. I have not solved my problem have you?
 
Hey sorry I just read this. I have not solved my problem have you?
Nope. When I opened the master cylinder, the front res (this would be for the rear brakes) was very low on fluid. I checked every inch of the lines and and all wheel cylinders and can’t find a drop leaking anywhere. I’m replacing the 2 lines on the rear end housing today because they were obviously bent by hand and look pretty funky. Then I’ll try bleeding again and replace the master if that doesn’t work and go from there
 
It Improves a little when I pump. The thing that gets me is that it was fine prior to the brake shoe swap. And I did not break into the hydraulic system or introduce air into it that I know of. I am going to try to re adjust and bleed as described. Just have to find time this weekend to do it.
When you changed the brake
shoes you've effectively
changed the required
volume of fluid in the
master.
Thicker shoes/less fluid.
Did you notice any fluid
leaking from the master
cap during the bleeding
process? On a single pot,
it may be benificial to
leave the master cap off
when bleeding the system.
Place a rag under it to
catch any fluid, and keep
the pedal depressions
slow and steady.
 
When you changed the brake
shoes you've effectively
changed the required
volume of fluid in the
master.
Thicker shoes/less fluid.
Did you notice any fluid
leaking from the master
cap during the bleeding
process? On a single pot,
it may be benificial to
leave the master cap off
when bleeding the system.
Place a rag under it to
catch any fluid, and keep
the pedal depressions
slow and steady.

Hi Thank you for the response. I have a dual pot master with front and back and no I did not see any fluid leak at any point. I was going to try cracking the MC brake lines to get any possible air out. I was also thinking of doing a fluid flush and replacing with new fluid as it has been a number of years. I will say the fluid color is not bad and there is no rust as the vehicle does not get many miles and is always garaged.

When flushing I was going to do the one man procedure using a bottle. Do you think I need to have the MC Cap on or off when pressing the pedal?
 
One guy on a forum gave me a suggestion that helps narrow down where a problem lies....He suggested to disconnect the lines at the master cylinder and put some sort of plug in each port to block them off....then press the pedal. If it is suddenly firm like it should be, your problem is not the master cylinder, it is somewhere downstream from it. If the pedal is still soft, the master cylinder is likely the problem.
Similar issue. Wanting to plug the master cylinder. The problem is trying to find the rear 9/16-20 inv flare plug.
 
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