I recently finished replacing the worn rear disk brake pads on our 2003 E450 chassis and thought that other DIY folks would be interested in the problems I encountered and the tricks I learned.
I have been doing brake jobs on my cars since the 60's and the change from drum brakes to disk brakes has made replacing the friction material, aka brake pads, so much easier than replacing brake shoes on the old drum style brakes. I figured that the brakes on the E450 were just larger, heavier versions of what I had seen on cars. While this is true, there are differences that made the job more difficult.
The first problem occurred after I had jacked up one side of the rear axle and removed the lug nuts. I discovered that the wheels wouldn't come off. The inside diameter of the wheel rim is a snug fit over the axle hub and rust that had formed in the tiny gap prevented the rim from moving. Application of Liquid Wrench, prying, hammering, etc. did nothing to break the rusty bond. After a half hour of struggle, I recalled reading about a trick to break rusted rims loose. I put the lug nuts back on finger tight, dropped the MH off the jack and drove a short way down the driveway. A sharp application of the brakes resulted in the wonderful clunk sound of the rim breaking loose from the axle hub. This trick works because the holes in the wheel rims are over sized for the lug bolts, so loose lug nuts combined with sharp braking causes the rims to move slightly against the hub.
Picture of oversize lug bolt holes and tight fit of rim on hub
After jacking the wheels back off the ground, I was able to wiggle the outer rim and after about 10 minutes of effort finally got it off.
Picture showing rust on hub before removing inner dual. The inner dual also required lots of wiggling to get it off the hub.
I had chocked both front tires as well as the duals on the other side before jacking, but I don't trust jacks. So I used the wood ramps that level the MH when it's parked in the driveway to catch the axle hub if the jack should fail or the MH fall off the jack.
The next problem was getting the caliper off. All of the cars I had worked on had caliper bolts to hold the caliper in place. The E450 rear brakes have caliper pins, which must be driven out of slots in order to remove the caliper.
Outer end of upper caliper pin circled in red.
There are raised bumps on the ends of the caliper pins to prevent the pins from working themselves out when going down the road. The service info I had downloaded from Ford said that there is a special tool to squeeze the end of the pin so that it can be driven out. The local Ford dealer didn't carry special tools, so I came up with another way to squeeze the end of the pin. In the picture below, the two flat blade screw drivers tapped in with the hammer act as wedges to squeeze the end of the pin, allowing the raised bumps to clear the edge of the slot.
A 3/8" ratchet extension was the perfect size to drive the pin out with some hammer taps.
Close view of end of pin with raised bump circled. The bump is shaped with a slope on the outer end so the pin can be driven into the groove easily when assembling the caliper. The sharp edge on the inside prevents the pin from sliding out. The pins are constructed as `a sandwich consisting of shallow V's of stainless steel with rubber bonded between.
The outer brake pad is attached to the caliper. This made it necessary to do some hammering and prying to get the caliper with pad off past the slightly thicker outer rim of the brake disk.
On the driver's side, the brake hose was long enough and had enough flex to allow the caliper to be removed from the disk. On the passenger side the hose was shorter and it was necessary to remove a support bracket where the hose was attached to the metal brake line.
Once the caliper was free, it was hung with wire to keep strain off the brake hose.
After removing the outer brake pad, a C clamp and a block of scrap wood pressed the two caliper pistons into the caliper.
A comparison of the old and new brake pads. The old pads had almost 81,000 miles of use and still had about 1/4" of friction material remaining. Might have been able to go another 20,000 miles.
Before installing the new brake pads, I cleaned the caliper pins and lightly sanded the caliper pin grooves and caliper surfaces that come in contact with the pads to remove rust. These surfaces were then given a thin coating of caliper grease, with care taken to keep the grease off the pad and disk friction surfaces.
Picture of the reassembled caliper.
Before installing the wheels onto the axle, I lightly sanded the rim/hub mating surface and applied a thin coat of caliper grease, in the hope that the wheels won't be rusted to the hubs the next time.
Inner wheel on greased axle hub.
Since I hadn't disconnected any brake lines in doing the job, there was no need to bleed the brakes. A few pumps of the brake pedal extended the caliper pistons against the new brake pads. A syringe removed the excess brake fluid that had been sent to the master cylinder earlier when the caliper pistons were compressed.
After finishing the other side I took the MH for a short drive. Brakes work fine, good for another 80,000 miles.
We generally coat the slider surfaces of calipers or caliper support with never-seize to reduce sliding friction inherent in application and self-adjustment.
Ditto the surface if the wheels to wheel hub to reduce the tendency for rust in that area. Rust is a problem in removal of the wheel, also if drum brakes are used, drum has the same problem in removal as do the wheels.
Another issue regarding rusting of the wheel or drum to the wheel hub is that loss of material can allow the wheel or drum to move out of concentricity with the wheel hub causing problems with balance and brake application. The wheels do not have to be many thousandths or an inch out of "true" to create a significant vibration.
It is to be expected that you bled the brake fluid to replace the fluid in the rear portion of the system? Old fluid has absorbed water and other contaminants from the air which increases internal corrosion and gumming up moving parts.
In order to bleed the system, the caliper bleeder nipples must be opened so this is the first thing a technicial does in servicing that area. It is much easier to free a tight bleeder nipple when the caliper is in place as opposed to loose and able to move around. If the bleeder nipple cannot reasonably be removed, it is more economic to replace the caliper and it is best to know this before remounting the caliper and pads only to have to remove it all again. The caliper lock "wedges" have a finite life so having to remove again may require replacement.
I noted that you used some "carpenter" C-clamps to push the caliper pistons back which indicated that your caliper pistons were not exceedingly tight. Otherwise those screw clamps would not have been able to effect the movement. It might be worth the mention that a tight caliper piston is an indicator that the caliper needs replacing. I don't know of anyone bothering to service calipers these days as replacements, either now or exchange, are so modestly priced.
The application of brake effort to the caliper pads should be as even as is possible, both within the caliper and on both sides of the axle. If the caliper is no able to slide easily, as noted above, the brake application will be higher to the pad on the piston side which makes for uneven application/release and excessive wear to the most movement resistant side. In addition, having resistance to release will cause the pad to drag after release, particularly after harder application.
This can cause excessive pad wear to the pad which is dragging, over heating, pulling of the vehicle to one side during braking and when brakes are released.
It is important to inspect the calipers for both proper movement in the mounts and also of the caliper pistons. We used to see many home brake jobs with big problems subsequent to the work.
Another caution is that some jurisdictions prohibit the service of brakes, steering or suspensions by other than a certified person. This came about because of public reaction to some horrendous accidents.
Good write-up, CloudDriver. I also like to block the axle hub when working on our rig at home. Seen a few which have come off stands but don't want to even think about that!
Like yourself, I too do a whole lot of brake work, and have to agree with NormK. But...
At the same time, you did nothing wrong. The few things you didn't do only reduced the duration for the next time you'll be playing with the same brakes. Instead of another 80,000 you might get 60,000....big deal. You'll probably won't own the rig long enough for that.
Basically it's all about prevention. You've got a few things going well. The surface of the disk/rotor looked beautiful. No scoring, no rust, appearing to be very flat, not in need of being cut or surfacing. Another point is that it appears the rotor and caliper have not been heavily subjected to winter salt. So any corrosion influenced trouble is greatly reduced. You did a very simple and very low cost brake job done right. Rest easy and enjoy.
The only things extra I would have done even for a "quick" brake job is...
1) Clean off the pistons before re-inserting into the caliper to avoid potential damage to each piston seal. If the dust boots did their job well, this might only be an inspection.
2) Replace the brake fluid. This assuming the bleeder valves are not rusted in place. If you get the bleeder valves loose, I would pump out all fluid out from the master cylinder, wipe out clean, then refill. Then remove the bleeder valves one at a time and let fluid slowly drain out while adding fluid up top to flow all the old fluid through the master cylinder, brake lines, ABS system, and proportioning valves. Then do a normal bleeding procedure after. Old fluid can jell up with moisture. Such contaminated fluid in all those systems can eventually introduce trouble, most often an ABS light coming on. Unfortunately by that time a system bleeding won't help. Time for a new ABS module. New fluid also makes your brakes perform better, much better than 10 year old fluid.
Also, I like to clean the threads on the bleeder valves and wrap them in plumbers teflon tape to prevent seizing and also for better bleeding.
Recapping much of what you did along with NormK, not in any particular priority or order
- clean piston walls before pushing them back into caliper
- clean & apply anti-seize to all points of rest, the ears of pads to caliper
- clean and lube the caliper slides
- cut the rotors
- regrease the bearings
- replace grease seals
- suck out and wipe out the master cylinder reservoir of as much fluid and dirt as is possible
- bleed/flush the brake lines with fresh DOT-3 fluid
- clean bleeder valves and wrap the threads in plumbers trflon tape
- clean mating surfaces, wheel to hub and apply anti-seize
- for the newer rotor design introduced in 2008, now separate from the hub like most cars, clean mating flat surfaces rotor to hub to assure true flatness to eliminate potential for rotor wobble/pulsating brakes, and add a thin layer of anti-seize to both surfaces as a corrosion preventative and for easy disassembly next time.
I wanted to add that I really like your tip of freeing the wheel from hub....driving a few hundred feet with loose lug nuts. That is tops!
Again, great job, great writeup. I didn't know about the caliper mounting pin clip design.
I should also have strongly emphasized that nothing done or recommended by CloudDriver was wrong. I also simply wished to expand on what he might have said excepting that fingers were likely already tired from making the long post.
Those E450 rear disc brakes use the same old Caliper Pins as the front disc brakes had on E-Series of the 1980s. This is odd since the Front disc brakes on the E450 are the more modern threaded pin style with boots to keep dirt off.
Between the two studs in the left side of the picture where OP greased the hub, you can just see an extra hole. On ours, I tapped that hole with 1/2"-20 thread. I can then turn a boat trailer lug bolt through the hole and it'll push on the hub, or the wheel next to it. The outer duals have to be mounted so the valves are one stud off of directly opposite so the bolt doesn't go into the corresponding hole in the inner dual.
God Bless, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100
Good trick, j-d. It was common practice on Japanese car the small truck brake drums back when dinosaurs still walked the earth. If the wheel is thick enough, as with these Fords, it can work well. Never could figure out why the Japanese would thread tiny little brake drums (which was an obvious and good thing) but the North American makers ignored this on much bigger and tougher stuff. Don't even get us started on transport trucks! Whaling away with a big sledge hammer to release some of those wheels is not for the faint of heart.