Duallie rear brake issue

[94f450sd]

Ive a customers duallie that keeps adjusting the shoes tighter.never had this problem, always been the backing off problem.I have replaced everything but the drums.gonna replace them tomorrow.

I even went as far as looking up how the shoes and hardware goes together to make sure the guy before me did it right.worse case ill pull everything out of my duallie and put it in his as I know my brakes work perfectly.gotta keep my customer on the road and happy.

Any help or ideas are appreciated.

 

[franklin2]

Just make sure the parking brake cables are not sticky. They all do it eventually, and it will look like a brake adjustment problem, but it really ends up being the parking brake cable not releasing completely.

 

[linkman440]

And make sure you have the self adjusters on the right sides

 

[94f450sd]

Just make sure the parking brake cables are not sticky. They all do it eventually, and it will look like a brake adjustment problem, but it really ends up being the parking brake cable not releasing completely.

Id say its possible but the ebrake isnt used and itll tighten itself up to the point of smoking within half mile after putting it together or backing the brakes off.

 

[franklin2]

Id say its possible but the ebrake isnt used and itll tighten itself up to the point of smoking within half mile after putting it together or backing the brakes off.

That could be the compensation port block in the master cylinder. Those are the ports in the bottom of the reservoir that push a geyser of fluid up when you step on the pedal without the cap on it.

When you are not pushing on the brake pedal, the master cylinder plunger retracts, and opens those compensation ports to the front and rear brake lines. As you drive down the road, the brake fluid warms up and expands. These open ports in the master give the fluid somewhere to go. If they are blocked, the expanding fluid starts applying the brakes.

A rod that is mis-adjusted between the booster and the master is a common problem, and anywhere there is something out of wack that would not let the master plunger retract all the way to open the ports up would cause this. I guess the ports could be clogged with junk also.

A quick dirty way to see if the master is being pushed all the time would be to loosen the mounting bolts to the booster a little bit and see if the problem when away.

 

[94f450sd]

Its not the hydraulic system.its something mechanical.it started off with the adjusting down problem.now it adjusts itself tighter.

 

[franklin2]

Its not the hydraulic system.its something mechanical.it started off with the adjusting down problem.now it adjusts itself tighter.

I believe you, but just to be positive, when they lock up I would go back to the shop, jack the back of the truck up, and crack one of the bleeders on one of the rear cylinders. If they are still locked up, then you can be positive it is mechanical.

After you verify it is mechanical, I would take the drums off, and take the cables off the self adjusters, one on each side. Adjust the brakes and then try it. If the problem goes away, then you will know it is the auto adjust system causing the problem. I will tell you when I bought my truck, someone had already taken these cables off for some reason, and now and then I have heard rumors of some of these auto adjusters not working right, but can't confirm there is a known problem with them.

 

[94f450sd]

Without the adjuster cables the adjuster will back off.this is the normal issue with fords.never had one do what this one is doing.I started off by replacing one of those cables to fix that problem.I know its not anything to do with the hydraulic system.I back the adjuster off all the way, go for a run and itll be tightened up before I get back to the shop.and its only one wheel thats doing it.if it was a system issue both wheels would be doing it.

 

[franklin2]

If you took the cable off, how can the adjuster back off? The cable is what pulls on the little wiper thing that wipes across the adjuster. When you back up and hit the brakes, the complete assembly shifts in the drum, and that's what pulls on the cable and it wipes across the adjuster teeth. I am here to learn new stuff though, so if you have a scenario of how this happens I would like to learn about it.

The only other thing I have had happen like this was when one or both of the wheel cylinders were old and corroded, and the springs on the shoes didn't have enough power to pull the wheel cylinders back in. But you said you replaced everything, so I guess those are new.

 

[79jasper]

Might've been covered somewhere, but what about the "wear spots" for the shoes? How do they look?

 

[94f450sd]

Might've been covered somewhere, but what about the "wear spots" for the shoes? How do they look?

They're perfect.only thing I can come up with Is the ID of the drums is too large.when adjusting you spread the bottom of the shoes to touch the drum.stepping on the brakes spreads the top of the shoes wich in turn pulls on the adjuster cable adjusting the brakes tighter.

 

[94f450sd]

If you took the cable off, how can the adjuster back off? The cable is what pulls on the little wiper thing that wipes across the adjuster. When you back up and hit the brakes, the complete assembly shifts in the drum, and that's what pulls on the cable and it wipes across the adjuster teeth. I am here to learn new stuff though, so if you have a scenario of how this happens I would like to learn about it.

The only other thing I have had happen like this was when one or both of the wheel cylinders were old and corroded, and the springs on the shoes didn't have enough power to pull the wheel cylinders back in. But you said you replaced everything, so I guess those are new.

When the cables break the flipper drops below the star wheel and no longer keeps the star wheel from turning.road vibration and pressure will cause it to turn in backing the brakes off.this is a very common problem with the fords.whoever came up with this design shoulda been fired.

 

[79jasper]

That's strange. Though I've never had any self adjusters work or even completely understood how they work, from reading I was under the assumption that they only self adjusted while backing up.
What about the wear on the top "pin" they ride on? Could that cause problems?

You said you replaced everything but the drums, did that include all new springs?

Last question, would it be possible to get a bad self adjuster cable? Like one that's a little too short.

 

[BigRigTech]

I've been having this issue with one wheel on my 92 for 3yrs...It always adjusts more than the pass side rear wheel. Not to the point of smoking but still a PITA. I replaced the cables and hardware - still does the same thing....I've learned to live with it I guess, one of my trucks "quirks"....Goes back to the whole theory.. or tires -it's going to give you trouble and it will be expensive...

 

[94f450sd]

That's strange. Though I've never had any self adjusters work or even completely understood how they work, from reading I was under the assumption that they only self adjusted while backing up.
What about the wear on the top "pin" they ride on? Could that cause problems?

You said you replaced everything but the drums, did that include all new springs?

Last question, would it be possible to get a bad self adjuster cable? Like one that's a little too short.

The ford design is supposed to adjust if needed everytime you step on the brakes unlike gms that are supposed to adjust by backing up slowly and hitting the brakes.

They usually dont work wich isn't a big deal.when the pedal feels low adjust the brakes a couple clicks.

All springs and hardware are new.everything thats part of the backing plates are perfect.

The cable is possible with the junk autozone is selling lately.but I grabbed a cable from my truck to try in it.