Reddit mentions of Centric Parts 136.65619 Clutch Master Cylinder

Hey there-- I had a 2000 Explorer Sport with a 5-speed. If yours is like mine was (and mine was identical to the 2000 Ranger) this might help. The shifter was stiff moving between gears, and sometimes I had to pump the clutch pedal to get it to move in or out of gear, especially when stopped.

The clutch is hydraulic.

The master cylinder is oriented in such a way that if the seals on the master cylinder piston are starting to fail, it has a tendency to pull air into the master cylinder, which gets trapped at the top of the piston, causing the clutch to get spongy and not fully disengage when you press the pedal all the way to the floor. Sometimes pumping it a few times will help temporarily, but it always comes back. You cannot bleed this bubble out of the system by pumping the clutch and using the bleeder screw.

This video shows the first thing I tried. It lets the air out of the top of the master cylinder without removing the cylinder from the car. It's awkward, difficult and messy. You'll want to cover the driver's side floor with a plastic trash bag and put something absorbent on top, like paper towels, to protect your carpet.

This worked for me... temporarily. IF THIS WORKED, chances are your master cylinder seals are going, which is why there was air in the system in the first place.

The permanent solution, for me, was to replace the master cylinder. It came complete with a fluid reservoir and the hydraulic line that goes all the way down to the quick-disconnect check valve at the slave cylinder on the clutch. It cost something like $65, and looks like this. Double-check to make sure that's the right one for your truck. When it arrived, I filled the system and did a full bench-bleed like this:

Ranger clutch bench bleed.

Hope this helps!