Launched in 1987, the Nissan Pathfinder is a versatile mid-size SUV. When you replace the brake master cylinder in your Nissan Pathfinder, bench bleed the new cylinder before installing it. This lessens the chance of pumping air into your brake lines after installation, which can cause spongy brakes. These steps only take about 10 minutes and apply to any year Nissan Pathfinder.
Tools Used: Replacement brake master cylinder (varies between models and years), Bench bleed kit (may come with the cylinder), Bench vise or clamp-on vise, Bottle of DOT 3 brake fluid, Philips head screwdriver
Bench Bleed a Master Cylinder
Remove the old brake master cylinder from your Nissan Pathfinder. It sits prominently on the driver's side of the engine bay behind the air box. If you're planning on reusing the old brake fluid reservoir, remove it from the cylinder and clean it out well. Make sure to dry it off completely before installing it into your new brake master cylinder.
Clamp the new Nissan Pathfinder brake master cylinder into a bench vise. If you don't have one of these, you can use a clamp-on vise to secure the cylinder to a work table. Make sure the cylinder is level.
Find the two fittings that came with your bench bleed kit and screw them into the outlet holes on the side of the master cylinder. Insert the two hoses from the kit into the fittings.
Bend the hoses up, so the ends sit inside the Nissan Pathfinder's brake fluid reservoir. You may need to cut them to the right length; they should stick about halfway down into the reservoir.
Pour fresh DOT 3 brake fluid into the reservoir up to the maximum fill line. The tubing will be submersed in the fluid, creating a hydraulic system. Be careful around your truck when pouring the brake fluid; if any fluid spills on the paint, clean it up right away using an old towel with soap and water to avoid damage to your paint job.
Get your Philips screwdriver and insert it into the Nissan Pathfinder brake master cylinder. Firmly push the screwdriver against the piston to start pumping the fluid through the unit.
Keep an eye out for air bubbles going through the system. You'll be able to see them coming out into the brake fluid. If you use clear hoses, this allows you to see the bubbles much easier; however, some brake bleed kits come with black hoses, and you may want to buy clear ones instead.
Pump the piston on the master cylinder until you no longer see bubbles coming out. Leave the hoses where they are and carefully unclamp the vise. Remove the cylinder from the vise and it's ready to install in your Nissan Pathfinder.
Tips & Warnings
Avoid letting the Nissan Pathfinder's brake fluid reservoir run dry, since pumping the cylinder without brake fluid will put air into the system and you'll have to start over. It's unlikely the fluid will get low if you put the proper amount of brake fluid in the reservoir to begin with.
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