Acura 46100-SD4-673 Master Cylinder Assembly (Nissin)

If your vehicle has an ALB brake system, skip this step because you need special tools that only mechanics who know what they're doing will have. Before choosing whether to replace the master cylinder, look at the costs of buying a new or factory-refurbished one compared to those of rebuilding it with a kit. The parts on a 1990 Legend master cylinder can't be repaired. The Brake Master Cylinder lives with the power brake booster in the engine bay. With a syringe, remove as much fluid from the reservoir as possible, then lay cloth under each fluid connection point. Put outlet covers (caps or plastic bags) on each line end you'll disconnect, moving carefully to avoid spill risk - any dropped brake fluid harms paint. Unscrew the tube nuts with signal flare nuts to protect the soft fittings from stripping. Push plastic caps on the master cylinder openings after pulling the brake lines away just enough to stop them from touching the master cylinder. First, disconnect the electrical connector at the master cylinder. Remove the nuts that hold it to the power booster, then pull the master cylinder off its studs and remove it from the engine compartment. You must get the right rebuild kit for the master cylinder, including all replacement parts, before trying to fix it. Open the fluid reservoir, remove the filter, drain whatever is remaining, and clean it. When working on Legend models, first unscrew the reservoir's hook and gently pull the reservoir off its place on the master cylinder body. Pull off the plunger's seal, shove in the second piston tube, and remove the snap-ring with special ring pliers. Fix the cylinder in a vice and push down on the secondary piston set with a screwdriver or punch. Take off the stop bolt afterward. Take off the cylinder parts in the same sequence, keeping note of the different press force on each spring. Unscrew and take off the screw that fastens the secondary spring to the piston in the secondary piston sub-assembly. You need a new master cylinder if the bore shows severe marks or damage. Rebuild using all rebuilding kit parts; clean and rinse parts using brake system cleaner, or use clean brake fluid; apply clean brake fluid to every component as you assemble. Reconnect the secondary spring to the piston by putting in its screw. First, place the built parts inside the master cylinder bore. Then put in the stop bolt with a fresh copper washer, and add the snap-ring and a new plunger rod seal. Place the reservoir back into its socket, making sure it goes down far enough into the master cylinder before fastening the hold-down screw. Before putting the new master cylinder in, place it in a vise and use threaded plugs to seal off the brake line holes. Fill the reservoir with the suggested brake fluid and press the piston assembly into the bore to push air out. Press until only brake fluid comes out of the holes. Don't stop filling until all air is removed to keep the tank filled. To connect it to the booster, set the master cylinder over the mounting studs and tighten the nuts by hand. Push in the brake line fittings into place on the master cylinder, where small movements remain possible. Then fully tighten the nuts and fittings. Pour brake fluid into the master cylinder tank, then make sure no air remains in sytem by draining air through brake fittings with an assistant pushing brake pedal down hard, and watch fluid until it is free from air bubbles, then test brake operation before returning vehicle to service.