I Will Brake You

Over the winter I noticed that one of my rear brakes began leaking fluid.  The fluid was leaking out of the brake drum and onto the wheel.  The leak was intermittent and seemed to only appear after a cold snap.  I knew this had to be the beginnings of a brake cylinder going bad.  Luckily, the previous owner (Hi Bob!) sent me a box of awesomeness after I had purchased the car.  This box contained 2 new brake cylinders, as set of brake shoes, and the brake hardware I needed to completely replace the rear brake setup.

Removing the old cylinders was easier than I had read; I'm guessing that is because I have the luxury of raising the car on a lift.  The locking clips securing the brake cylinder were not hard to remove and the brake hard lines weren't so corroded that I could not remove them.  I'm glad I didn't experience some of the horror stories I had read online.

After removing the old hardware I cleaned the backing plate thoroughly.  This is important since through 1976 Datsun used a single piston wheel cylinder that moved in the backing plate to keep itself centered as the pads wear.  Once the area had been cleaned I used 3M Silicone Paste to lubricate the sliding area as well as all shoe pivot points, taking care not to get the paste near the braking surfaces.  At this point it is worth mentioning: make sure the self adjusting mechanisms are oriented correctly before installation.  For many this won't be an issue, but apparently some of the parts between the two cylinder boxes were swapped (the adjusters and emergency brake arms are configured for one side or the other); I ended up removing one of the cylinders after realizing this fact.  In the below picture the entire self adjusting mechanism was actually on the wrong side.

After ensuring the cylinders were configured correctly, I set the retaining clips into place using some wide-jaw channel locks to squeeze the two clips towards one another.  I used new springs and pins to secure the new shoes as well.

Once the shoes were set I installed the brake drum and used the following process to set the initial adjustment:

1. With the drum in place use a large screwdriver or other long blunt object and a rubber mallet to gently tap the new cylinder towards the back of the car just until contact is made.  This sets the rear shoe against the drum.
2. Open up the adjustment hole on the drum and position the hole just over the adjustment collar on the front side of the cylinder.
3. Use a screwdriver to turn the adjuster until the front shoe contacts the drum.  
4. Back off the adjuster about 1/4 a turn or so.
5. Rotate the drum to ensure there is no binding.  Some resistance is OK, but there shouldn't be a lot and you should be able to turn the drum by hand.

In my case I didn't plug the ends of the brake lines and instead let the brake master cylinder drain completely.  After attaching the hard lines to the backs of the cylinders, I used my power bleeder to run fresh fluid through the lines and bleed the brakes.  I let the car sit overnight and bled them one more time to get the last of the air out of the system.  

As a final step I took the time to adjust my parking brake appropriately, removing a lot of slack that had accumulated from years of cable stretch.  For the first time since I've had the car the emergency brake handle does not need to be vertical to engage the brake!

After a couple of test drives this weekend, I have no evidence of leaks and the brakes are working as expected.