Excessive Front Brake Drag

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Cudakid2967

Cudakid2967

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So went to go take a look at front brakes on our 67 cuda and realized could barely spin the rotors they were dragging so much. KH small bolt disks. Just replaced the master cylinder with the doctor dif plastic top. Did notice that cracked the bleeders it squirted out and then if I pull back on the brake pedal it lets them spin again. Does this mean the push rod is too long or is there something else need to be looking for? Also if it is the push rod is there any work arounds or do just need to get a adjustable push rod
 
Well, the pedal should be parking up as far as it goes. If you can lift it and the lifting causes the pressure to release, that right there tells you something is not right. Find outwhat is causing this, and fix it, and all should be well.
 
Make sure the master cylinder is connected correctly AND that there is NOT a residual pressure valve in the "disc" end of the master. Normally the rear section. Many times an incorrect rod or adjustment, holding the piston "down some" will cause them to lock up
 
AJ/FormS said:
Well, the pedal should be parking up as far as it goes. If you can lift it and the lifting causes the pressure to release, that right there tells you something is not right. Find outwhat is causing this, and fix it, and all should be well.
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What I am asking the question for. I am trying to figure out why it is doing that and trying to get ideas on what to be looking for
 
Can you pull the brake pedal towards the rear of the car an inch or so?


The reason I'm asking the questions I am is to rull out things.


KH front brake calipers have 4 pistons, each piston returns back to a released position due to the seals deforming when pressure is applied and returning to their origional shape.


Things that would hold the front brake caliper are...

1. Wrong seal, they should have a rectangular cross section.
2. The bore of the calipers being rough
3. The master cyl having a residual pressure valve in the rear most port(for the front brakes)
4. A flexible brake hose with internal defect or old age
5. The mc piston not returning to its full relaxed position
6. Front wheel bearings too tight
7. Front wheel bearings lack of liberation
8. You could have issues in the distro block etc as well.

My assumption is that before the mc change everything worked as expected, is that correct?


Are you sure you have a problem?
 
Dana67Dart said:
Can you pull the brake pedal towards the rear of the car an inch or so?


The reason I'm asking the questions I am is to rull out things.


KH front brake calipers have 4 pistons, each piston returns back to a released position due to the seals deforming when pressure is applied and returning to their origional shape.


Things that would hold the front brake caliper are...

1. Wrong seal, they should have a rectangular cross section.
2. The bore of the calipers being rough
3. The master cyl having a residual pressure valve in the rear most port(for the front brakes)
4. A flexible brake hose with internal defect or old age
5. The mc piston not returning to its full relaxed position
6. Front wheel bearings too tight
7. Front wheel bearings lack of liberation
8. You could have issues in the distro block etc as well.

My assumption is that before the mc change everything worked as expected, is that correct?


Are you sure you have a problem?
Click to expand...
It doesn't come back that far, maybe 1/3 to 1/2 inch.
As far as we know, everything was working correctly before changed mc. Have had everything apart, do know wheel bearings are good, spun nice and free and smooth.
Potentially hose, but did replace one know recently and both sides were dragging hard and then released and spun correctly again with the slight pull back of the pedal.
Would not correct distribution be causing master to not return correctly? After some slight test do know rears are locking up first(9 inch drums) and have a proportioning valve we need to put into it.
 
Oh my GAWD. Everybody tries to make this harder than it is. Here's what you do. Duplicate the condition where the front brakes are locked or dragging. Now. UNBOLT the master cylinder from the firewall leaving EVERYTHING still connected. Brake pushrod, brake lines....EVERYTHING. Then try to turn the front wheels. If they turn, the pushrod is too long for that master cylinder. This is a REAL common issue changing from one master cylinder to another, OR when replacing a master cylinder with someone's reman as they all have a little different tolerances. REAL simple to figure out in less than five minutes. I don't know why these guys try to complicate it all to hell and back.
 
RustyRatRod said:
Oh my GAWD. Everybody tries to make this harder than it is. Here's what you do. Duplicate the condition where the front brakes are locked or dragging. Now. UNBOLT the master cylinder from the firewall leaving EVERYTHING still connected. Brake pushrod, brake lines....EVERYTHING. Then try to turn the front wheels. If they turn, the pushrod is too long for that master cylinder. This is a REAL common issue changing from one master cylinder to another, OR when replacing a master cylinder with someone's reman as they all have a little different tolerances. REAL simple to figure out in less than five minutes. I don't know why these guys try to complicate it all to hell and back.
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Happened to me once. I just made an aluminum shim to put between the firewall and MC. As RRR said I loosened the MC a little and the brakes stopped dragging.
 
RustyRatRod said:
Now. UNBOLT the master cylinder from the firewall leaving EVERYTHING still connected. Brake pushrod, brake lines....EVERYTHING. Then try to turn the front wheels. If they turn, the pushrod is too long for that master cylinder. This is a REAL common issue changing from one master cylinder to another, OR when replacing a master cylinder with someone's reman as they all have a little different tolerances. REAL simple to figure out in less than five minutes. I don't know why these guys try to complicate it all to hell and back
Click to expand...
If the brake pedal can move toward the rear of the car. The pedal is not stopping the mc from returning all the way.


There is no return spring on the pedal so the internal springs in the MC are the only thing returning the pedal. If the weight of the pedal is causing the MC to be pressurizing the system there is a much bigger issue with the MC.
 
Dana67Dart said:
If the brake pedal can move toward the rear of the car. The pedal is not stopping the mc from returning all the way.


There is no return spring on the pedal so the internal springs in the MC are the only thing returning the pedal. If the weight of the pedal is causing the MC to be pressurizing the system there is a much bigger issue with the MC.
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Unless he's checked the wheels for free movement when he pulls the pedal back, he doesn't know that. It makes ZERO sense for him to not try it. It's either two or four nuts is all he has to loosen. Five minutes.
 
Cody Scollay said:
Would not correct distribution be causing master to not return correctly? After some slight test do know rears are locking up first(9 inch drums) and have a proportioning valve we need to put into it
Click to expand...
More details please.


There is a possibility when replacing parts brake lines got switched to the wrong ports?
 
RustyRatRod said:
Unless he's checked the wheels for free movement when he pulls the pedal back, he doesn't know that
Click to expand...
My assumption is that nothing is stopping the pedal from moving back (1/3 to 1/2" of rearword free travel) so the mc should be in it's full off position.

On a manual brake car the length of the push rod basically sets the height of the pedal, UNLESS there is a up travel stop, friction, or an obstruction.


Maybe the brake light switch bracket needs to be adjusted and that is keeping the pedal from returning to full off position.
 
Dana67Dart said:
My assumption is that nothing is stopping the pedal from moving back (1/3 to 1/2" of rearword free travel) so the mc should be in it's full off position.

On a manual brake car the length of the push rod basically sets the height of the pedal, UNLESS there is a up travel stop, friction, or an obstruction.


Maybe the brake light switch bracket needs to be adjusted and that is keeping the pedal from returning to full off position.
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I try not to assume anything. That's usually where the trouble is. lol
 
If either of us were on site I bet we could find the root cause in no time.

If we were both there at the same time it would take a week!

:poke:

:rofl:
 
Dana67Dart said:
If either of us were on site I bet we could find the root cause in no time.

If we were both there at the same time it would take a week!

:poke:

:rofl:
Click to expand...
I suspect you're right. It sucks over the internet.
 
Yeah, I could probably fix it in five minutes because it's not my car! lol If it was mine it would take a week !:BangHead:
 
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