How do you remove the original rear hatch struts on a 1990 Mazda 323?

This is a fairly simple repair operation, but best performed with a helper to hold the hatch open. There are two bolts holding the bottom bracket, and a ball joint bolt at the top. It's easiest to unbolt the ball joint bolt at the top first, then lay the strut down toward the tailight out of the way to remove bottom bracket bolts. It's best to replace both struts at the same time, if one is worn out then so is the other likely to be, and it's hard to figure out which one is weaker anyway. They cost less than $50 each from Mazda which is cheap insurance. Try to buy replacement struts that come with the ball joint bolt already attached, as it is very difficult to remove the ball from the strut on original equipment if you need to reuse it. Some aftermarket struts used to come this way, but they may not be as strong as the OEM equipment from Mazda (as I found out on a 1986 Mazda 323 - rear window washer/wiper option required a heavier duty unit). But you can recover the ball joint bolt from the old strut with a little extra effort, and a hack saw or dremel tool to saw through the strut socket head at several angles until the ball can be pulled from the socket. Hold the strut in a bench vise, especially if you are using a hacksaw. You can pry off partially cut through pieces with a screwdriver or hammer and chisel. NOTE - Be careful not to saw into the ball or damage it's surface so that it can still articulate smoothly in the socket of the new strut. Be sure to wipe it clean as it's likely to be coated in old grease and fine metal filings from normal wear and tear. Fortunately it is very easy to install the ball into the socket of the new strut. They come already greased with a bigger opening and spring clip to hold the ball in the socket once it's inserted. Just push it into place, no tools required for this step. Now reinstall the new struts in the reverse order of the steps above. Be careful to identify which is right and left before bolting in place. (Check that the ball joint bolt at top is facing toward the hatch). Tighten bolts snug but don't overtighten or you could strip the threads. Your new struts should hold the hatch firmly open. If not, you probably have the wrong parts.