As typical, the rubber caps over my master cylinder reservoir level sensors were split and falling apart. You can buy new ones for $7 each, but I didn't want to wait, plus I am cheap. In my fittings bin, I had some soft protective caps that fit the sensors. These ship inside tube fittings to keep out debris, so if you work in an industrial setting which uses hydraulics you might salvage some from the trash bin. They weren't quite tall enough to sit securely by friction without pressing down on the floats and tripping the sensors, so I secured them closer to the edge w/ super glue.

These caps serve more than just keeping gunk off the floats. I expect they are also critical in keeping moisture in the air from being absorbed into the brake fluid (main source of corrosion). Thus, replace yours if any loose or split. I use DOT 5 silicone fluid in my 300D's, so less concern (that starts endless arguments). I suspect new rubber caps would only last a few years since every one I have seen in use had splits.

BTW, if any sharp eyes noticed the routing of the vacuum tube from my "blue moon" to the transmission modulator, that is a temporary tee'd tube to a vaccum gage in the cabin to monitor the shift signal.

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