Replacing Toyota MR2 engine drive belts, or accessory belts as they are commonly called, is a key repair. Drive belts wear over time because of the heat in the engine bay and stress placed on the belt by the continuous tension placed on it. The belt begins to crack and eventually breaks, causing one of your accessories to fail. To prevent this scenario from happening and getting stranded, inspect your belts periodically and replace if necessary.
Loosen the lock bolt with a ratchet and loosen the belt tensioner until the belt is loose enough to remove. The Toyota MR2 uses multiple drive belts rather than a serpentine belt and therefore requires that each belt be removed separately with its own lock bolt and tensioner.
Pull up the engine accessory (alternator, water pump or A/C pump) and push down repeatedly until the belt comes out without significant force.
Install the new drive belt onto the engine accessory and crank pulley.
Tighten the tensioner until the belt only has approximately a half-inch of deflection. To check, you can use a ruler and place it vertically against the belt. Push down on the belt and measure how far down you were able to push it. If you are able to push it more than a half-inch, it is too loose. If you aren't able to push down to a half-inch, the belt is too tight and could cause accessory damage.
Tighten the lock bolt to keep the tensioner in place
If you cannot reach the tensioner or lock bolt with a ratchet, you may need to use a small wrench to get to them.
Wear safety glasses to protect your eyes from injury.