Brakes dragging question

[AussieinNC]

MoFormula...

Your issue sounds like the new booster pushrod thats goes into the master cylinder is set too deep...

To test this out...remove the two nuts that mount the master to the booster and add two metal washers over each stud, then replace the master cylinder and retest...

If the symptoms have gone away, remove the two nuts again and adjust the push rod in the booster to reduce the length that goes into the master...two washers is usually about an 1/8th of an inch....

It only takes a small amount of excess length in that rod to not allow the master cylinder piston to not open the return ports fully, keeping slight pressure in the circuits, essentially riding the brakes...

Also, if you also changed your master cylinder, make sure the front circuit outlet port does not have a residual line valve in that port...remove the front metal line and use a paper clip to probe into the port seat...if you feel a rubber valve in there it needs to come out of that front port...

4 wheel drum brake masters need those residual line valves in place in both ports,,,disk brake systems should not have residual line valves in any circuit feeding a disk system,,,either front or rear...

[rockyrivermark]

Originally Posted by AussieinNC

MoFormula...

Your issue sounds like the new booster pushrod thats goes into the master cylinder is set too deep...

To test this out...remove the two nuts that mount the master to the booster and add two metal washers over each stud, then replace the master cylinder and retest...

If the symptoms have gone away, remove the two nuts again and adjust the push rod in the booster to reduce the length that goes into the master...two washers is usually about an 1/8th of an inch....

It only takes a small amount of excess length in that rod to not allow the master cylinder piston to not open the return ports fully, keeping slight pressure in the circuits, essentially riding the brakes...

Also, if you also changed your master cylinder, make sure the front circuit outlet port does not have a residual line valve in that port...remove the front metal line and use a paper clip to probe into the port seat...if you feel a rubber valve in there it needs to come out of that front port...

4 wheel drum brake masters need those residual line valves in place in both ports,,,disk brake systems should not have residual line valves in any circuit feeding a disk system,,,either front or rear...

I appreciate that but mentioned early in my post that the pushrod has been adjusted and definatly not out too far. I also tried the washers behind the master.
The master cylinder is definitely a disc/drum master.
Smaller back res.
The only thing left is proportional valve. Currently it's the original combination valve from the drum/drum system
I'm gonna replace that along with all new lines this fall.
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[RichardJ]

>>The only thing left is proportional valve. Currently it's the original combination valve from the drum/drum system<<

YOU DON'T HAVE A COMBINATION VALVE !!!

You have a Pressure Differential Switch. Fluid from the MC for the Front brakes goes in the side and out the bottom. Fluid for the Rear brakes goes in the other side and out the bottom. A sealed piston sits between the two and doesn't move if both pressures are the same. Any failure in the front or rear system causes the piston to move, closing the switch, turning on the Brake Failure Warning Light.

You don't have a wire connection on your switch. You don't have an way of knowing it you have correctly bled the rear brakes. I told you in an earlier post that with only a Switch Block and NO COMBINATION VALVE AND NO PROPORTIONG VALVE, your rear brakes should easily lock up and skid the rear tires.

Do you even have Rear brakes?
Are the Front brakes doing 100% of the braking?
Are the Front brakes actually dragging or are they just getting Hot?
Are you ever going to jack up one of the front wheels to see if it is dragging?

[AussieinNC]

Hey rockyriver,

My comments were intended for MoFormula...sorry for the confusion...

and

RichardJ...crikey mate...maybe its time for a Snickers bar....haha

I enjoy helping folk out, I find it relaxing really...and it keeps this old mind active...

We all need to remember that a percentage of our forum members are "yungins" that are on here to ask questions and figure out how we all used to actually repair our equipment, rather than just replace components or the actual item...

Now...everyone go play nicely !

[rockyrivermark]

Originally Posted by RichardJ

>>The only thing left is proportional valve. Currently it's the original combination valve from the drum/drum system<<

YOU DON'T HAVE A COMBINATION VALVE !!!

You have a Pressure Differential Switch. Fluid from the MC for the Front brakes goes in the side and out the bottom. Fluid for the Rear brakes goes in the other side and out the bottom. A sealed piston sits between the two and doesn't move if both pressures are the same. Any failure in the front or rear system causes the piston to move, closing the switch, turning on the Brake Failure Warning Light.

You don't have a wire connection on your switch. You don't have an way of knowing it you have correctly bled the rear brakes. I told you in an earlier post that with only a Switch Block and NO COMBINATION VALVE AND NO PROPORTIONG VALVE, your rear brakes should easily lock up and skid the rear tires.

Do you even have Rear brakes?
Are the Front brakes doing 100% of the braking?
Are the Front brakes actually dragging or are they just getting Hot?
Are you ever going to jack up one of the front wheels to see if it is dragging?

I haven't been able to drive the truck as I've had some recent issues following a back surgery.
Lighten up Francis

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