Rear brake rebuild: Part 3 (final)

The third and final installment of the rear brake rebuild project – putting it all back together.  Once I got everything installed, I bled the system using the old-fashioned method.  Martha manned the brake fluid reservoir and brake pedal, while I operated the bleeder valves, starting with rear-right, left-rear, front-right, and finally front-left.  I did not use my homemade pressure bleeder because I feared cracking the old plastic fluid reservoir. I think I get a better result from the old-fashioned method, and it gives the family a chance to get involved in keeping the bus moving (or in this case stopping).  As always, I used DOT-3 fluid.  With the system bled, I adjusted the brakes.

For Part 1, click here

For Part 2, click here


We last left off with the packing plate treated for rust and parts installed on the plate. I took the rubber boot seals off the wheel cylinder so I could better orient the slots on the pistons. Removing the boots isn’t really necessary, but live and learn.  Some recommend using brake fluid to lube the cylinder.  The Bentley manual suggests brake fluid paste.  I did neither, per advice from some who say the treatment is not really necessary and taking the cylinder apart can cause other issues.

Using a large screwdriver, I rotated the piston slots into approximate position for the brake shoes.

Shoe installation works from top to bottom, the reverse of removal. After putting the wheel cylinder boots on the shoes (again, they can be left on the cylinder), I inserted the shoes into the slots.

I suppose the one advantage to removing the boots is that it makes it easier to see if the shoes are fully seated.

Both boot seals placed back on the cylinder.  Once the shoes are seated in the cylinder, the bottoms are inserted into the slots on the star adjusting screws (adjust the screws in as far as the will go, but do not tighten them into the star adjuster).  It takes both hands to spread the brake shoes and seat them in their slots, hence no picture of this process.

It’s advisable to add a little anti-seize to the lip on the shoe retaining pin. This is where the head rests on the backing plate so this step will prevent the two from rusting together.

The retaining pins are inserted from behind the backing plate and through the hole in the shoes.

Retaining pin at home once again.

Retaining pin sticking through the shoe.

Like the retaining pin and other parts, I rust-treated the spring cup and shoe retaining spring.

The cup simply sits on top of the spring.  Rotate the slot in the cup to match the retaining pin flare orientation (I kept everything vertical for easy alignment).

The cup and spring assembly needs to be compressed to get the pin flare through the cup slot. Once that is accomplished, the spring and cup rotate 90 degrees to lock the pin in place (there is a little indentation in the cup were the pin flare seats). Normally, all of this can be done with just fingers, but my digits got a little tired after a few failed attempts. The socket (11-mm I think) worked as a great substitute. With the socket method, I needed to reach behind the backing plate to rotate the pin (instead of the spring/cup assembly) to lock it all in place.

Shoe retaining pin flare seated in its notch (90 degrees from the slot).

Both pins installed along with the cups and springs.

Insert the larger hook on the lower return spring into the rear-side shoe, second hole from the bottom, first. Then insert the smaller front hook. Doing so in reverse causes headaches.

Small lower return spring hook aligned with proper hole in front-side shoe. Installation takes two hands and a pair of needle-nose pliers to stretch the spring and maneuver the hook through the hole.

Lower return spring hooked up to the shoes.

Last to be hooked up is the parking brake cable. Installation is reverse of removal. Push the brake lever forward (to front of bus) while bending the cable down so the slot-hole at the end can slide onto the brake lever hook.

Voila. I can park on a hill again!

All parts back in place. Time to double check the seating of all parts and center the shoes as best as possible. If the star adjusters aren’t fully retracted, the drum won’t go on very easily.

I read somewhere that this is the perfect time to add some grease to the wheel bearings.

The best tool for adding grease to an already installed bearing is a grease needle on a grease gun.

Insert the needle into the bearing, between each roller, and pump grease until it forms a blob around the rollers. Be careful not to to add too much as the grease might drip on braking surfaces. I also tried to keep it off the bearing seal.

The new grease is a little tough to see in the bearings here, but it looked good in person. I also added some grease to the wheel shaft splines.

The wheel hub slides right over the wheel shaft.

Yellow arrows point to surfaces that often provide difficulties when taking the rear wheel assemblies apart and will benefit from, you guessed it, anti-seize. The backside of the hub castellated nut (not the threads), front of wheel hub where the nut seats, and the lip between hub and lug nut plate where the drum sits.  At this point, I only tightened the castellated nut with a breaker bar to hand tight.  That’s tight enough to test the system before putting the bus down on all four wheels and torquing these nuts to spec (do not torque with bus lifted!).  Then I installed the brake drum and torqued the two drum bolts to 22 ft-lbs.

The brakes can be adjusted using a screw driver, but the curved ends on a brake spoon prevent damage to the backing plate adjusting holes and makes spinning the stars much easier.

Rear, right wheel.  There are three holes in the backing plate. The forward hole (green arrow) is the brake shoe inspection hole. Through this hole we can keep an eye on the adjustments to the front shoe and, over time, brake shoe wear. The rear hole (yellow arrow) is the brake adjustment hole for the front-side shoe, the star adjuster can be seen above the spoon.  The brake adjustment hole for the rear shoe is hidden in the shadow on the right.  Turning the stars clockwise expands the brake shoes, making them engage the drum.  On the front star adjuster, this means pressing the star points down, towards the floor.  On the rear-side adjuster, the star points get pushed up.  I used the following steps when adjusting the brakes (which are basically the same as outlined in the Bentley manual, but with a few modifications).  In a nut shell: Loosen the parking brake cable by undoing the nuts at the base of the handle in the cockpit.  Press the brake pedal several times to center the shoes.  Adjust the front-side shoe out until the drum moves with difficulty. Back the shoe off until the drag on the drum barely disappears.  Repeat for rear-side shoe.  Press pedal a few times once more and readjust the shoes as before.  Repeat once more if needed (desired).

With the passenger side completed, I headed over to the driver side. This one went a lot faster now that I knew what I was doing.  This side got the same treatment already discussed. As they say, “If one wheel cylinder leaks, the other also leaks or soon will”. Mine was definitely leaking.

Earlier, in Parts 1 and 2, I mentioned that I broke the clip that keeps the parking brake spring from passing through the backing plate. I was rushing the second brake work a bit and did not pull straight back, thereby tearing off a piece of the clip. These clips are NLA, so unless one has spares or access to a parts bus, an alternate will need to be found\made.

In box of spare hardware, I found a window shade bracket that had the perfect thickness and rigidity to match the original part.

The bracket also had a nice hole in the middle for the cable to slide through. I cut the two ends off the bracket with a hacksaw and used the center portion for the clip.

A little action on the grinding wheel shaped the bracket nicely while a hacksaw cut the slot through to the hole.  Although not pretty, it worked beautifully.

Before moving on to installing the wheels and torquing the castellated nut, I wanted to include a couple of pictures of the wheel cylinder issue that I discovered, almost accidentally, after adjusting the passenger side brakes. This photo shows the newly installed cylinder. Note the clip on the piston sits right next to the wall of the cylinder. This is how they should look, even after adjusting the brakes. Once I completed the first side, I adjusted the brakes per Bentley manual and all seemed OK, except for a slight rubbing or drag on the brake drum that I could not adjust out. It wasn’t much and I was really ready to move along, but something in the back of my head made me take the time to pull the drum – just to double check my work.

I was very glad I heeded my instincts because I found that the pistons were not seating correctly  after stepping on the brake pedal. No matter what I tried, I could not fix the issue. A little research revealed that 1: the vendor sent me the wrong cylinders (an inexpensive version) and 2: This was a common problem with the inexpensive version.  This problem can also be caused by a bad master cylinder, pressure regulator, or deteriorating brake lines.

After some haggling with the vendor, they agreed to send me the ATE cylinders I ordered, free of charge and told me to keep the junk ones for paper weights. Unfortunately, they still didn’t get me the correct cylinders and I wound up with the middle of the road Brazilian ones. I didn’t have time to wait for a second shipment, so I just installed them. The vendor refunded me the difference in price so I won’t name them BUT always verify your parts when they arrive!!. The cheap cylinders came in an unmarked box and instead of assuming they were correct, I should have been on the phone asking. Oh well, it’s all good in the end. Here is the Brazilian cylinder installed. To date, after 500+ miles, they still work fine and I see no evidence of leaks. Come winter storage, I’ll take the wheels off and do a detailed visual check. I’ll report back the results when I do.

In order to properly adjust the brakes, the parking brake cable must be loosened (a task that might be necessary to get the drums off as well). Before tightening the cable, I installed the wheels – lug nuts just hand-tight. Then I pulled the parking brake handle out 6-clicks. With a screw driver in the slot on the cable end (just to the left of the right side green arrow), I used a 10-mm box wrench on the lower nut to tighten the cable. I did this until the wheel turned (using both hands) with moderate-high resistance. Then I tightened the other cable until the second wheel turned with an equal resistance to the first wheel. Next, I stepped on the brake a few times and repeated the process.  Finally, after a third round, I deemed all was good. As soon as Moby came out of the garage, I applied the parking brake on a slight incline to make sure the parking brake kept the bus from moving.

Satisfied with the parking brake and shoe adjustments, Moby came off the jack stands for the final torquing of the castellated nut and lug nuts. The castellated nut gets 240 ft-lbs of torque, which is quite a bit. I used my cheater pipe and 3/4-inch breaker bar (formulas for calculating the length of the pipe+bar needed per body weight and torque value are found in John Muir’s Idiot Guide manual and the web). I can’t remember the length used here since my father long ago marked the pipe for maximum distance the breaker bar is inserted into the pipe. I get the correct torque by standing on the bar during final tightening (no bouncing on the bar) – this method works well for the flywheel gland nut too. A impact wrench would also work of course, but that’s a tool I have yet to acquire. The lug nuts have a low enough torque value that I can use a normal 1/2-inch torque wrench, but I’ve tightened these often enough over the years that I know how much force is needed on my lug nut wrench.  NOTE:  The red arrow highlights a scrap of vinyl magnet (intended to cover house HVAC vents) that I used to help protect the paint from the cheater pipe.

Ideally, the hole for the cotter pin aligns between the turrets on the nut after tightening, but, if it doesn’t, tighten the nut some more – 247 is the minimum torque so you don’t want to loosen the nut to align the hole.

Cotter pin slides in between the turrets and through the hole in the wheel shaft.

After bending the ends on the cotter pin, Moby was ready for a test drive. I always take the lug nut wrench and a few other tools with me – just in case I missed something. We live on a hill so the brakes got their first test quickly out of the gate. All worked well during the test and after double checking the lug nuts when I got home, I put the rubber dust caps in the backing plate brake adjustment and inspection holes, snapped on the hubcaps, and went camping! It was good to be back on the road!


4 thoughts on “Rear brake rebuild: Part 3 (final)

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

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

  3. Excellent write up. If your plastic reservoir is old and brittle, wouldn’t you want to replace it now and know that job is done ? I also replace the rubber hoses, they look ok as they get old but close up internally,

    • Thanks! Great points. Yes, I would replace the reservoir if degraded to the point of being delicate. I just meant that the plastic doesn’t seem as flexible as it once was and I didn’t want to put undo pressure on it with the bleeder. I agree about the rubber brake lines. The point you make is one of the reasons pistons might not return to their correct positions in the cylinder. Happily, my rubber lines are relatively new, but I do keep an eye on them (well so to speak). Thanks taking the time to comment!

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s