Rear Brake Overhaul

This procedure applies to late Buses from 1971-1979 with the composite rear drum setup (meaning you don't have to remove the 46mm axle nut to remove the brake drum). It is similar to the procedure I have already written for Vanagons but there are enough differences to justify a separate procedure.

The main difference between Vanagon and Bus brakes is that Vanagon brakes are self-adjusting while Bus brakes are not. Dealing with those adjusters, which are often rusted in place, can make Bus brakes a headache.

This procedure came about when I had to replace the rear wheel cylinders, brake shoes, and brake adjuster hardware on my '79 Westy. I didn't originally buy the adjuster hardware but I should have, since I wound up having to do this job twice in a short period of time. The adjuster hardware (4 adjuster nuts, 4 adjuster screws) is cheap and readily available and you really should replace it when you do a brake job unless you know it to be in good condition.

So let's get started then. First, chock one of the front wheels, set the parking brake, put the Bus in gear, and then remove the hubcaps from the rear wheels. Then loosen the lug nuts but do not remove them. After that is done, jack up the rear of the Bus and support it on jack stands. Then remove both rear wheels. After the wheels are off, remove the two 11mm bolts from each brake drum. These bolts are what hold the drum to the hub. Once they are off, go into the cab and gently release the parking brake and put the transmission in neutral. Then go back and remove the drums. Hopefully they will pull right off -- they should. First make sure you can rotate them without problem, if you hear the brake shoes scraping the drums as you rotate them, you may have to go and back off the adjusters a bit to get the brake shoes out of contact with the drum. The adjuster holes are found on the other side, toward the bottom of the brake backing plate. They should be plugged with rubber plugs. If not, put the plugs on your shopping list. They are very cheap and keep water and other crud out of the brake drums. I forget which ways you have to turn the adjusters to loosen them, it varies from wheel to wheel and adjuster to adjuster. One way tightens, one way loosens, figure it out by trial and error. You may also find that the adjusters are frozen and will not turn. You will fix that once we get inside the drums.

If you still can't pull the drum off, try some taps on the drum with a rubber mallet to loosen it up. Sometimes rust forms between the drum and the hub and they kind of weld themselves together. If this has happened you may need to beg or borrow a puller to get the drum off.

At any rate, the drum is now off. Look at the scene before you and meditate on it. Observe the parts and their functions. At the top is the wheel cylinder. It bolts to the backing plate and a steel brake line screws into it. The top ends of the brake shoes sit in cups on the wheel cylinder. When you push the brake pedal, brake fluid is pressurized and pushes into the wheel cylinder, then pushes the two pistons outward, forcing the brake shoes against the drums and slowing the van. Neat, eh?

Down at the bottom you see the adjusters. The part that you turn with a screwdriver sits in the bottom of the backing plate and a threaded screw is inserted in each, with the brake shoe bottoms sitting in the slots in the screws. When you turn the adjuster star, the threads move the screws in or out of the star, thus moving the brake shoes toward or away from the drum. This allows you to set the clearance between the shoes and the drums. You will note that over time as the brake shoes wear, the clearance increases and the pedal has more travel before the brakes seem to really function. It's at that time you need to crawl under the van and adjust the brakes to bring the clearance back in line.

There are also two springs that connect the two brake shoes. These are to pull the shoes away from the drums when the brake pedal is released. There is also a cable that comes into the lower part of the backing plate and hooks onto a lever which is attached to the rear brake shoe. This is the parking brake cable. When you pull on the parking brake, the cable pulls the lever which forces the brake shoes into contact with the drums. You'll note this system is completely independent of the hydraulic system which means it will work even if the hydraulic system fails, which is why it is often called the "emergency" brake. But also note that it only works on the rear wheels, so it's effectiveness in slowing the van would be poor, but better than nothing.

So now that we have identified how it works, let's take it apart. First step is to remove the lower spring. Get a pair of pliers on it and then disengage it from one of the brake shoes, then simply pull it out of there. Set it on the ground somewhere in the correct orientation.

Now unhook the parking brake cable from the lever it attaches to. Push the lever forward with your finger while you pull the cable downwards. Sometimes it takes some fiddling but it will eventually pop off.

Now disengage the bottoms of the shoes from the adjusters. Just pull them out of the slots they sit in. Now do the same with the top ends -- remove them from the slots they sit in in the wheel cylinder. It may take some fiddling since that top spring is pretty strong, but you can get them out of there. Then lift the shoe assembly out and set it on the ground.

The next part is a little tricky. The shoes are held together by a heavy spring and a crossbar. The crossbar is held to the spring with a metal clip. You need to first remove the clip. A pair of pliers will generally do the job. Then you need to remove the crossbar. Basically to do this you need to pull the two shoes apart, which takes a little strength because you are working against that spring. But when you get them far enough apart, the crossbar will fall out. Try to pay attention to its correct orientation so you can put it back together correctly. Once the crossbar is out, the shoes can be twisted 90 degrees to detach them from the spring.

Next you want to remove the adjusters, especially if they are rusty and don't turn. Usually the screws will turn in the adjusters but the adjuster stars will not turn in the bores they sit in. If that's the case, you can unscrew the screws from the adjusters with a big screwdriver (Liquid Wrench would be good to use here). Removing the stars from their bores is a bit more of a challenge. But thankfully there is an easy way to remove them which I highly recommend. Thread a suitably long (longer than the adjuster screw) M8 (I think that's the correct size) into the adjuster star. When the bolt gets to the bottom of the bore, keep turning and it will pop the star right out. This works SO well. Save that magic bolt that works for this in a baggie and label it.

Once you have removed the adjusters, hit everything with a good shot of brake cleaner. Hose down the backing plate with the stuff, and the hardware bits you have already removed. Get everything nice and clean.

Now we're gonna replace the wheel cylinder. If you don't have to do this (yours isn't leaking) then skip ahead but otherwise, read on.

The wheel cylinder is held to the backing plate by a single bolt and by the steel brake line. First crack the brake line loose with your wrench and then loosen the bolt that holds the cylinder to the backing plate. Get your new cylinder ready before you crack the brake line loose because as soon as you do, fluid is gonna start dripping out. So loosen the line all the way and then remove the bolt, then withdraw the wheel cylinder. Make sure the threads on the steel line are clean, then put the new wheel cylinder into position. Start the mounting bolt but keep it loose, then start the brake line. Tighten the brake line down finger tight, then tighten the mounting bolt down. Then go ahead and finish tightening the brake line. That's about all there is to wheel cylinder replacement, except that now you have to bleed the brakes -- but we will do that later.

Now break out your new brake stuff -- shoes, hardware, adjusters, backing plate plugs. First step is to assemble the new adjusters. First coat the insides of the adjuster bores with grease. then coat the adjuster star itself, then the threads of the adjuster screws with grease. You want them to be free for a long time. Then insert the adjuster stars into their bores, tap them into place. Then insert the screws into the stars, and turn them down as far as they will go with the slots remaining vertical (to hold the brake shoes, you know).

Next, you gotta assemble the new shoes. You may find that yours come with the parking brake lever already installed. If so, good for you, if not, install it. I've never had to install one so I'm not sure what's involved, but I think it's usually staking a rivet or bolting the lever on. Make sure that you set the lever up to be on the rear shoe or you may curse yourself later. Then go ahead and put the big spring on the two shoes, and then the crossbar the same way it came off. You generally have to put it back on the same way -- grunting and pulling the two shoes apart against spring tension to put the bar in. Once the bar is in, install the clip to clip the spring to the bar. This looks like it's gonna be really hard but is not too bad with a little thumb pressure and some pliers.

Once the shoes are together, install them. Get them into position and then insert the tops into the slots on the wheel cylinder, then the bottoms into the slots on the adjusters. Once that's done, push the parking brake lever forward and hook the cable end onto it. Then go ahead and install the bottom spring with your pliers. Next step is to put the drum back on.

Once you get this far, go over and do the other side the same way. The first side will take a while, the second will go much faster once you know the drill.

OK, so once the actual parts replacement is done, you gotta bleed the brakes. Rather than rehashing that procedure here, I will refer you to the Karmann Ghia master cylinder replacement procedure since the bleeding procedure is the same. Just scroll down until you get to the part about bleeding the brakes, then come back here.

Now that you've got the brakes bled, you need to adjust them. Crawl under and find the adjuster holes in the backing plate (they are toward the bottom). Turn the adjusters to tighten the adjustment until they won't turn anymore (and the wheel is locked). Make sure to turn both of them all the way out this way. Then back off each adjuster one turn at a time with the screwdriver until the wheel spins not quite freely. You want a little brake shoe scraping noise as you spin the drum, but you don't want it bound up or freewheeling. Guesstimate it, you can always change it later. Once you think you are done, get up and go push on the brake pedal 3 or 4 times. This re-centers the shoes in the drums and you may find your adjustment is not as right as you thought it was. Re-adjust as necessary, then fit the backing plate plugs into their holes.

Once you get that far, put the 11mm nuts back in the drums, then re-mount the wheels. Snug the lug nuts down, then lower the van back down, then tighten the lug nuts to spec with a torque wrench. I believe the spec is around 100 ft-lbs. Put the hubcaps back on, and go for a test drive. I imagine you will notice the parking brake feels a lot better and so does the brake pedal. Enjoy!

Sean Bartnik
September 16, 1999

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