How strong should E-350 parking brake be? - Page 2

Ford_6L_E350 · 01-20-2014, 12:27 PM

Since I normally drive a manual transmission, I shift into Park first, then with my right foot still on the service brake I push the parking brake down with my left foot.

Mike

carringb · 01-20-2014, 01:32 PM

Oil on brake pads can cause a "glaze" on the drum. This has to be removed to restore braking performance, otherwise the pad/shoe material cannot deposit onto to iron surface. When I encounter this, I use scothbrite pads to knock down the glaze, preferably on a die-grinder otherwise it takes forever to get it all off. Or you could just have them turned.

Chance · 01-20-2014, 06:17 PM

Quote:

Originally Posted by carringb

Oil on brake pads can cause a "glaze" on the drum. This has to be removed to restore braking performance, otherwise the pad/shoe material cannot deposit onto to iron surface. When I encounter this, I use scothbrite pads to knock down the glaze, preferably on a die-grinder otherwise it takes forever to get it all off. Or you could just have them turned.

Agree. I'm thinking new pads (again) and turned drums might do it. Probably should have insisted on turning drums last time instead of good cleaning to de-oil.

Seems like a bad design if oil leak affects brakes that easily. I owned many old cars with rear drum brakes and minor leaks never caused a brake problem like this.

carringb · 01-20-2014, 08:17 PM

Quote:

Originally Posted by Chance

Seems like a bad design if oil leak affects brakes that easily. I owned many old cars with rear drum brakes and minor leaks never caused a brake problem like this.

This problem is inherent to any live axle with drum brakes. You may have not noticed on your cars because they didn't have as much weight to hold back, or made as much torque to overpower the rear brakes.

One of our fleet trucks had rear drums (Chevy 3500 Cab/Chassis). We could never get axle seals to last more than a few months because the truck was overloaded empty. First sign of failing seals? No rear brakes. Pretty scary on truck that could tip 18,000 combined. With front brakes only (and marginal ones at that), it would take half a block to stop from 25MPH.

Chance · 01-21-2014, 09:17 AM

Quote:

Originally Posted by carringb

Quote:

Originally Posted by Chance

Seems like a bad design if oil leak affects brakes that easily. I owned many old cars with rear drum brakes and minor leaks never caused a brake problem like this.

This problem is inherent to any live axle with drum brakes. You may have not noticed on your cars because they didn't have as much weight to hold back, or made as much torque to overpower the rear brakes.

.......cut.........

Another factor is that normal brakes wear out both the pads and drums on regular basis, so they at least have some means to decrease oil accumulation. By comparison parking brakes shouldn't wear out hardly at all, or heat up. That's why I think the design is a little weak. I agree all rear drum brakes on live drive axles are vulnerable to oil, but parking brakes seem more so.

I wonder if this is a typical design, because I owned a Ford RWD car with rear discs that used the calipers for parking brake.

carringb · 01-21-2014, 10:50 AM

Drum-in-hat is much more common than using the calipers as the parking brake. Seem to be that once you get to midsize cars they move to drum-in-hat. I suspect it's because larger pistons wouldn't leave enough space for the cam and cable, but I really don't know for sure.

Once you move larger than a 450/4500 truck, they all go to drive-line mounted drum brakes (unless it has air brakes), and most of those mount to the transmission, which means they still have the oil-contamination problem when a seal goes.

Do you have a semi-float axle? Often premature seal failure on the semi-float axles is because there's enough wear on the axle shaft to allow some play at the seal. I have the full float, and did the seals at 250k, and they were only seeping just barely.

ANZAC · 01-21-2014, 11:14 AM

Mine is bad but I think I have rusted cables and rusted hardware inside the hat.

I got a kit of springs etc to recondition the hardware. Need to figure out which cable sections need replacing.

Chance · 01-21-2014, 12:59 PM

Quote:

Originally Posted by carringb

Drum-in-hat is much more common than using the calipers as the parking brake. Seem to be that once you get to midsize cars they move to drum-in-hat. I suspect it's because larger pistons wouldn't leave enough space for the cam and cable, but I really don't know for sure.

Once you move larger than a 450/4500 truck, they all go to drive-line mounted drum brakes (unless it has air brakes), and most of those mount to the transmission, which means they still have the oil-contamination problem when a seal goes.

Do you have a semi-float axle? Often premature seal failure on the semi-float axles is because there's enough wear on the axle shaft to allow some play at the seal. I have the full float, and did the seals at 250k, and they were only seeping just barely.

May also be due to drum brakes can be made more powerful with same amount of mechanical force. My old Mustang with drum brakes didn't even have power booster and it stopped well. With disc brakes it's hard to stop without assistance. Leverage isn't as good. Maybe with smaller and lighter cars the disc/caliper parking brake is good enough, but may not work on a van weighing 3 times as much.

I haven't taken my axle apart but it looks like a full-float to me. I'm also under the impression that all 15-passenger Super Duty E-350s use full-float axles. I recall reading that on a spec book a long time ago but can't be certain.

Anyway, the seals were replaced at around 120,000 miles almost two years ago in an attempt to make the parking brake stronger so the van would pass state inspection. Now I'm looking at the same problem again in a few months.

Ford_6L_E350 · 01-21-2014, 01:54 PM

Quote:

Originally Posted by Chance

May also be due to drum brakes can be made more powerful with same amount of mechanical force. My old Mustang with drum brakes didn't even have power booster and it stopped well. With disc brakes it's hard to stop without assistance. Leverage isn't as good. Maybe with smaller and lighter cars the disc/caliper parking brake is good enough, but may not work on a van weighing 3 times as much.

I haven't taken my axle apart but it looks like a full-float to me. I'm also under the impression that all 15-passenger Super Duty E-350s use full-float axles. I recall reading that on a spec book a long time ago but can't be certain.

Drum brakes are usually self energizing. Normally one shoe is self energizing for forward motion and the other for reverse motion. Sometimes they are both self energizing in the forward direction; those don't work as well as discs in the other direction. Disc brakes are not self energizing, but can be made to work without power assist by sizing of the master and slave cylinders, at the expense of pedal travel.

Full floaters came on some versions of E350s, but it varied by the years. Easy to ID a full floater, remove the hub cap, if the surface is almost flat behind the wheel, it is a semi-floater. A full floater has a flange that sticks out ~4" past the wheel.

Mike

Chance · 01-21-2014, 03:04 PM

Mike, like I said, it looks like a full float to me. Maybe not quite 4 inches sticking through wheel but probably over 3 inches anyway. Unless Dana has completely redesigned the axles internally, the wheel end looks just like a smaller version of the ones running on F-650s and the like.

I can honestly say that most if not all Ford E-350s I've noticed without hubcaps have been full float. It's surprising that full float is the exception instead of the standard.