I rebuilt my master cylinder today. Not bad at all. My symptoms were a generally soft brake pedal, in fact recently it got so bad I couldn't generate enough grab to lock the wheels at higher speed.

The kit that comes from Nissan includes a new stopper cap, lock bolt o-ring, and new pistons/seals. It does not include the seals that go between the reservoir and master.

Disassembly: Put a catch pan under the car. Remove the 2 12mm nuts that hold the MC to the brake booster (hint: use your knock sensor tools!). Unplug the low fluid level sensor. Using a 10mm flare wrench nut, loosen the two brake tubes. Have some paper towels handy and use your fingers to plug the openings that are now draining fluid. Remove from the car. Clean it off as best as possible, as all external dirt will try to become internal once you get to rebuilding it.

Now use a thin, narrow flathead screwdriver to pry out the tabs on the stopper plate. Discard the plate. Working over a catch pan, tap the MC on something firm and the primary piston will fall out. Now remove the check bolt and discard it's o-ring. Tap on the MC again and the secondary piston will fall out. Discard both pistons. Using a paper towel and something that can't scratch, clean the inside of the cylinder and inspect inside in good light. If there are any scratches, just give up now since it's not rebuildable. Mine had 185k and was spotless inside. It's optional to remove the reservoir - if you bought new seals then pry carefully and don't break it.

Reassembly:
Take the secondary piston, lube the seals with a dab of clean brake fluid, and insert, making sure the slot is horizontal. (The check bolt must line up and pass thru this slot). Now insert the primary piston. Press the primary piston partway and insert the check bolt with a fresh o-ring. Finally, put on the stopper plate. It will snap in.

Now fill the reservoir. If you have the tubing and fittings to bench bleed it, do so. I didn't, so I held a paper towel over both ports and used a phillips head screwdriver to pump the cylinder. As the paper towel got wet with fluid at the ports, I held my finger tight over it and prevented air from being drawn back in (thus drawing fluid from the reservoir instead). It seemed to work well enough. I installed the MC assembly into car by first attaching the brake tubing and low level sensor connector. Then I washed the whole thing down with a garden hose and tightened the 2 12mm nuts.

I was rebuilding my front calipers, so I went on and did that before bleeding the brakes. But bleed your brakes and you're done.

Dave

 

I bet you saved around 500 bucks doing that yourself. I had mine replaced at about 220k miles.

 

nice write up. How long it took?

 

I could do it all again in an hour, not including the bleeding. The bleeding is the more time consuming step, and that depends a lot on what bleed method you use.

 

I got the vacuum pump brake bleeder. I helped a friend out this weekend and it was so quick to use. The best way to bleed the brakes and making sure no air gets in the system.

 

Hmm, let's see, I've tried:
- 2 man manual method
- speedbleeders
- power bleeder
- vacuum pump

The vacuum pump didn't work for me. I suspect the catch container wasn't seal properly, so that sucked. There are a lot of fittings that can leak and draw air into the system. I prefer pressure-based methods for that reason alone. I did spend $70 for the silverline plus kit which has the best pump unit that Mityvac makes, btw.

Speedbleeders are great but you need to spend like $50/vehicle to change them over. Fast and work without a helper.

The powerbleeder is good (but it's annoying to set up and you have to take it off each time the reservoir gets low, so it's not very fast.) But it always works the first time and it works with one person.

Edit: I just learned today that it's designed so you fill the pump container with some brake fluid, so you don't have to take it off the reservoir. So you just pour your liter of brake fluid into the Motive container and wash it out when you're done. Wish I had read the directions better!!

The manual method works well and fast but I always work alone.

 

You can build your own pressure bleeder with a few basic components. There are plenty of websites that give how-tos.

I purchased one of these kits a while back and it works pretty good.
It uses the air from one of your tires to pressurize the system.

http://www.speedibleed.com/

It is pretty pricey for what it consists of though.