Below are some pictures of a brake master cylinder from a 2004 mercury marauder 300B

Here is the master cylinder, the salvage yard inserted red colored plugs into the brake pipe and fluid reservoir cap ports to keep brake fluid from leaking out and moisture from leaking in

This master cylinder didn't have any obvious problems, but the car no longer needs this part since it was wrecked and is being parted out by an automotive recycling facility.

Here is the master cylinder after disassembling it.

Inside, this master cylinder looks very similar to the 1998 crownvic master cylinder that i previously disassembled. The main differences are that there is no equalization valve between the two brake pipe ports. And the front port is an M12 instead of the M18 one that accepts a proportioning valve. Even the part numbers stamped onto the pistons are the same on both master cylinders.

Here is the main casting from the brake pipe port side

Here is the main casting from the top where the reservoir would normally insert. Pay attention to the part that looks like a plug in the port on the right

That thing that looks like a plug is actually a piston top rod

Here are the pistons & springs from inside the master cylinder.

Here are the pistons again with the piston stop rod inserted into the one on the right

And the piston stop rod laying above the piston

The bottom piston has some sort of pressure relief system in it. Despite being colored bronze instead of green, this piston assembly appears identical to the one from the 1998 crownvic master cylinder and has the same casting number stamped into it.

Here are the seals which normally retain the reservoir to the master cylinder. Ford has been using these seals on bendix master cylinders since they switched from cast iron to aluminum ones in the 1980's.

Here is the piston that the brake booster rod normally inserts into

And here is the piston pulled apart into individual peices. The retaining screw is not "bottomed out" from the factory, and you can compress the spring more by tightening the screw down.

This is the connector from the reservoir fluid level sensor. The same connector is also used on the alternator regulator in crownvics that have 6G alternators.

Here is the reservoir from the top

And the reservoir fluid level sensor

Here is one of the caps that the salvage yard inserted into the master cylinder. The writing on it reads "BROCK AUTO SUPPLY CO. TEMPE, AZ 1(800)528-4400 CPT 16" You can visit this company on the web at:

Here is the snap ring that normally holds the pistons inside the master cylinder

And here is a 1998 reservoir laying next to the 2004 marauder reservoir. Notice how the 1998 one on the left has yellowed versus the 2004 one on the right?

The 2004 marauder that this master cylinder came from was about 3 years old when it was wrecked and the master cylinder appears to have been stored indoors away from sunlight since. The 1998 master cylinder by contrast has spent 12 years outside exposed to sunlight that leaks into the engine bay. Nylon yellows after many years of sunlight uv exposure.

I have a collection of crown victoria master cylinders. Here are the reservoirs from them. The one on the left is from a 2004 police car without traction control, the one in the middle from a 1998 police package with traction control, and the one on the right from a 2004 grand marquis (marauder package) with traction control. Notice how the master cylinder on the left is wider than the rest? and how the one on the left has a different partioning system for the brake fluid within the reservoir?