Side sills not draining?
Ever wash your car and notice that the water doesn’t drain from around the top as fast as it used to? There could be a good reason for that! The side sill drain holes are susceptible to dirt, leaves and other debris. One key indicator – after washing or a heavy rain, a sloshing noise that sounds like it is coming from the bottom of the door(s) can be heard due to trapped water. This, of course, could cause Mister Rust to visit one day! There are four sill drain holes per side – two in front of, and two behind the door. Periodically, I like to clean the openings with a pipe cleaner. If you have a pair of ramps, it makes it all that much easier. But beware – you will get dirty!
REF 1994 Mazda Technical Services Bulletin