Rear brake rebuild: Part 1

Like clock-work, Moby normally is on the road, after hiding from the winter’s salty roads, by April each spring.  March is always a time for wrapping up the winter to-do list, going through some regular maintenance items, and verifying all is well.  However this year, the sliding door project and some some work on the CHT sensor (future post) pushed emerging from hibernation back into mid-April.  After an oil change, valve and carb check, and some attention to a loose fan belt, she was ready to see the sun once again, albeit a few weeks later than normal.  Still, with our first camping trip a few weeks out yet, we had time to spare.

The first drive of bus season is always wonderful. To have the road out in front, the engine purring behind, and no urgency remotely close, one can just sit back, relax and enjoy – it is almost like going on a mini-vacation.  Though gratifying as this drive may be, it is always a short one, a shakedown if you will, to see what parts might fall off.  I cannot say they all were problem free over the years, but that is kind of the point and with spring weather in full swing, fixing any issues is not really a chore.

Upon arriving home after this year’s test drive, one I thought was a complete success, I pulled into the garage to give the lights and engine one last visual check.  When I checked the lights before the trip, I focused on the big ones: brake, turn-signal, rear-side markers, and headlights which all checked out fine.  Once back in the dim garage however, I noticed the license plate light was out – a ticketable offense!  I bent down, wiggled wires, and gently tapped on the engine lid to no avail.  As I turned to shutdown the engine and grab a screwdriver for removing the lens and bulb, I noticed a white shadowy movement from the corner of my eye.  Bending down and looking under the muffler I did not see much, but then I caught movement again near the garage door.  Looking into the sunlight, I could see a faint tendril of white smoke drifting out of the garage. My first thought was that the valve cover was leaking again, but I found no oil drips.  Nor did the smoke have a bluish tinge or smell like burning oil.  With a flashlight I followed the white wisps to the source – the right, rear wheel.  While the smoke did not smell like burned brake shoes, there was obviously a problem as the drum was hotter than the left-side drum.  The semi-sweet odor made me think of brake fluid, although I never have had the honor of experiencing burning brake fluid.  The backing plate and outside of the drum appeared dry, though dirty, but a wheel cylinder leaking all winter way not have released enough fluid to coat the outside, just the inside of the drum which in turn contaminated the shoes.  If the shoes were sticking, as indicated by the high temperature of the drum, the fluid would start to smoke.  An investigation was launched, and herein lies this, first of three posts.

Close to twenty years have passed since I last worked on brakes and I forgot all the little tricks that help make the job goes faster.  Dealing with the first wheel took me at least double the time that it should.  Hopefully, this post will save others (and my future self) time.  There can also be a lot of rust-related headaches involved with this job, especially if the leaks occurred over an extended period of time, and those headaches eat up time and patience.  Luckily, Moby’s PO was a fan of anti-seize when he assembled the brakes years ago.  He made the job a lot easier for me, so I send out many thanks to Kevin for his attention to such things.  Oh, and the license plate light, yes I fixed that too.  A new bulb took care of that.

For Part 2 click here

For Part 3 click here

First step: inspection of the offending passenger side rear brakes. I jacked up the rear of the bus, put it on jack stands for stability, and removed the wheel. After taking out these two bolts, the drum should slide off the hub, however, the drum often rusts to the hub and needs a little help. I used a lead hammer to gently persuade the drum but it still held fast. Sometimes the parking brake and brake adjusters need to be loosened to let the drum slide past the brake shoes which I only had to do for the passenger side (this was also the smoking side), probably because the wheel cylinder was sticking.

With the drum off, it was easy to see that the wheel cylinder was leaking.  If one leaks, the other either already is or will soon.  Change them both, along with the shoes, at the same time.

It’s hard to see in the picture, but the brake dust covering the cylinder had a wet, shiny appearance due to the leak, which apparently started some time ago.

The brake shoes were also contaminated with fluid. Any shoe/pad in this condition needs to be replaced, which was a shame in this case because there were lots of stopping miles left on these.

Disassembly begins with removing the shoe retaining pins, shoe retaining springs, and spring cups. The pins pass through the backing plate and shoes, holding the latter in place by locking into the cup sitting on the top of the spring (red arrows). To remove, push and rotate the spring/cup until the slotted hole in the cup aligns with the flared end of the pin and unlocks the pin (better pictures will follow later in this project – it’s hard to work and photograph at the same time).  Note the front shoe was soaked in brake fluid as well (green arrow), but it was already destined for the trash heap as both shoes should be replaced at the same time.

With the spring cup and shoe retaining spring out of the way, the shoe retaining pin slides out the rear of the backing plate (if it isn’t rusted to the plate).

The entire brake job can be completed without removing the castellated hub nut and wheel hub. However, the hub is constantly in the way and I find it much easier to work with it removed. This of course, assumes the castellated nut plays nicely. Torqued to 253 ft-lbs they can be tough to remove and are even worse if rusted. But I like a challenge, so, late in the game, I decided to remove the hub. If you’re reading this thread before you start the job, I HIGHLY recommend this as your first step should you choose to remove the hub.  Removal also provides a chance to inspect the axle seal, wheel bearing, and repack with grease. In order to undo the castellated nut, the cotter pin must be removed by folding its legs straight and tapping the pin through the nut with a hammer.

With the pin legs tapped down even with the nut, I inserted a pair of needle-nose pliers into the  cotter pin eye and then tapped the pliers to remove the pin.

Now comes the fun part. IMPORTANT NOTE! The bus must be on the ground – do not do this with the bus jacked up or on stands as the force needed to remove the nut is considerable. Following this rule, I had to backtrack a bit by reinstalling the wheel, removing the stands, and lowering the bus to the ground.  I then chocked the other three wheels to keep the bus from rolling (applying the parking brake will help too). A 3/4-inch breaker bar with a 46mm socket is best, smaller breaker bars have the tendency to bend/break. In this picture, I have a 3-foot cheater pipe, to help with leverage, that I slowly leaned on, applying all my weight to break the nut loose.  Not getting very good results, I then stood on the pipe while gently bouncing. If using this technique, be careful of the paint along the wheel-well (red arrows) and the corner of the rear bumper (green arrow).   Later in the project, I found a sheet of refrigerator magnet material to stick to the bus and protect  the paint.  Also, be careful to not fall off the cheater bar!

Unfortunately my castellated nut was uncooperative, most likely due to rust (it’s worth mentioning here that there is debate about putting anti-seize on very important nuts, like this one and lug nuts, because it might interfere with torque readings. Moby’s PO did not use anti-seize on this nut, which is fine by me). After coating the nut with penetrating oil and letting it sit, I tried unsuccessfully to remove it once more. With more penetrating oil and a half-hour of whacking the breaker bar with a hand-held sledge hammer, I finally got the nut moving. Oddly enough, the other side came right off with just the cheater pipe.

And now… back to the brakes!  Brakes changed a lot over the years so they may look very different from the ’71 version seen here. With the hub removed, I wrapped the axle with a paper towel and rubber band to keep the dirt out. The parking brake cable (running below the axle) must be unhooked from the brake lever attached to the rear shoe, a task much easier with the hub out of the way.  Push the parking brake lever (just in front of rear shoe) forward (front of bus), while grabbing the cable and pulling down and then slightly towards the back to unhook the eye from the lever.  Next, the lower return spring (red arrow) can be removed by grabbing the end towards the front of the bus (you want the end with the shorter hook) with needle-nose pliers and pulling forward (blue arrow) while gently rotating the hook out of the hole (back end of blue arrow).  With the spring out of the way, spread the bottom of the shoes apart (yellow arrow) and extract the lower tabs from the star adjusters.  Finally, spread the top of the shoes (green arrows) to get them out of the wheel cylinder and remove the whole shoe assembly from the backing plate.

Undoing the brake line from the wheel cylinder with a 10mm box wrench.  Once disconnected, I wrapped the brake line in plastic bag and rubber band to help contain the dripping brake fluid.

Now the wheel cylinder can be removed by taking out this 13mm bolt.

These too can rust in place, but with a little twisting and penetrating oil they pop right out.

Brake fluid attracts moisture and will cause rust. Since I took the time to remove the wheel hub, I decided to remove all the parts and do a thorough cleaning. In this photo, I’m removing one of the star adjusters. They simply slip out of their holes. I feel like I keep repeating myself, but rust is the major hang up with these. While mine were coated in anti-seize (thank you PO Kevin!), one of my previous bus’s adjusters were not. To get them out, I substituted a bolt in place of the adjuster screw (in my hand in photo), clamped vice-grips around the bolt, and hammered the star adjuster out. This destroys the threads on the replacement bolt, so don’t vice-grip the adjuster screw!

The star adjuster consists of two parts, the adjuster (left) which slides into the backing plate and the adjuster screw (right, in my fingers) which holds/spreads the brake shoe. Brakes are adjusted by turning the star from behind the backing plate, which extends or retracts the shoes via the adjuster screw.

The backing plate is bolted on with two 17mm bolts just above the star adjusters (seen here) and the wheel cylinder bolt. Since the plate was covered in brake fluid, I thought it’d be easier to clean if I took it off the bus.

Before the backing plate comes off, the parking brake cable must be removed. To do this, I grabbed the spring with my left hand and pulled the spring back, releasing the tension on the clip that keeps the spring from slipping through the hole in the backing plate. With the tension gone, the clip was removed with needle-nose pliers by pulling the clip out and letting the cable slip through the slot in the clip. Be careful! If the cable is not aligned with the slot, the clip can break when you pull and these are NLA parts! I broke the driver side clip, so you’ll see a fix in part 3.

I couldn’t pull on the spring, remove the clip, and take a picture at the same time, so here is a shot of the spring, backing plate hole and the space needed to remove the clip.

The parking brake cable has a fixture at the end of the rubber housing that slides snugly into the backing plate. A coating of the silver stuff, aka anti-seize, will keep them from rusting to the plate, but if they are rusted, vice-grips and a hammer are your friends.

Once free, the cable slides out through the hole, spring and all.

Despite some time spent on the endeavor, the backing plate would not come off regardless of penetrating oil or gentle hammering. The plate held fast to the metal mounting peg (red arrow). It was also rusted to the wheel shaft and bearing housing, although I eventually got that part loose. After reading a bit on the subject, I found more hammering, heat, and even driving the peg out from behind the backing plate were all sound options, but I wanted to move along with the project and I didn’t want to damage the plate (new ones aren’t cheap).   Since I only needed to clean the plate, I just left them on the bus.  For cleaning, I used FLAPS brand brake cleaner and a brush while being very careful not to get any solvent on the axle or wheel bearing seal.  The back of the plate was a bit more time consuming, but a little perseverance paid off.

Time to tackle the brake shoe assembly – a pretty easy job. The two shoes are held together by the upper return spring just visible under the connecting link near the top of the shoes. The parking brake lever is on the left, parallel to the rear brake shoe. The spring below the whole assembly is the lower return spring I removed a few photos above.  I left it in its proper installed orientation, note the shorter hook on the right.  This is the side that is removed first.

There is a clip (yellow arrow; can be seen in place in the above photo) that attaches to both the connecting link and upper return spring (green arrow). With both hands on the top part of the shoes, the clip is removed by using each thumb to press the spring towards the connecting link and, at the same time, pull the spring towards the viewer of this picture. This releases the spring from the curled end of the clip, which then falls off the connecting link.

The parking brake lever must come off before the connecting link and upper return spring.  To accomplish this, I drove the horseshoe clip backwards with a screwdriver and hammer to open the clip’s arms and created a little space on the opposite side of the retaining pin.

With a screwdriver inserted between the pin and clip, I rotated the blade and removed the clip from the pin.

Horseshoe clip removed. The pin needed a little help from a drift and hammer to drive it out of the brake shoe and brake lever.

With the pin out, the brake lever slides out towards the top of the shoes.

Brake lever removed.  At the bottom, the notch for the cable is visible.

The shoes are then separated from the connecting link by spreading the shoes and rotating one shoe towards the viewer of this photo. The link drops out, leaving just the return spring holding the shoes together.

Remove the upper return spring by rotating the shoe away from the viewer of this shot and off the spring’s hook. Repeat for the other shoe.

The shoes got tossed into the trash as the brake fluid contamination made them useless. The remaining brake parts received the same cleaning as the backing plate. Keep in mind, brake cleaner is pretty rough stuff on skin, making nitrile gloves useful for this task.  I then removed, disassembled, and cleaned the driver side brakes.  That side’s wheel cylinder was also leaking but not a badly as the passenger side.  Even if thosed brake shoes were not contaminated with fluid, I still planned on their replacement so I could have new brakes on both side.

Stay tuned for Part 2 of this project thread due out soon!



2 thoughts on “Rear brake rebuild: Part 1

  1. Pingback: Rear brake rebuild: Part 2 | Zero to Sixty . . .Eventually

  2. Pingback: Rear brake rebuild: Part 3 (final) | Zero to Sixty . . .Eventually

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