How do you tighten the belt on a 1993 Probe?

Actually there are 2 different tensioners used.

On the 4 cylinders engine there is a spring hooked up to the tensioner bearing plate. If that one breaks you will have to replace the belt and also check the engine for faults since the 4 cylinder engine is an interference engine eg. the valves can (95% of the times) hit the pistons and bend.

Location: Top of engine in the middle of the two cam sprocket wheels.

On the 5 cylinder engine there is an hydraulic tension piston that pushes on a notch on the tensioner bearing plate.

It can be pressed back into place if one takes it off from the engine (2 bolts) and place it in an vice and gently and slowly presses the piston back in until you can push a tiny allen key through the hole and lock it in position.

If there is no resistance in the push rod and you can push it back with your hands you will have to get an replacement.

You can how ever reuse the timing belt if it looks in good shape (best is always to buy a new belt) if needed in an emergency.

The 6 cylinder engine is also a non interference engine which means that the pistons and the valves don't collide.

Location: Low to the back of the short side on the engine.