by Robert Bowen
(Taken from BMW 3-Series (E30) Performance Guide 1982-1994 by Robert Bowen)
Timing belt changes are a frequent fact of M20 ownership. It’s not hard to do on your own if you have a few hours.
1. Start by draining and removing the radiator, cooling fan, hoses, and accessory belts.
2. Remove the distributor from the end of the cam and use a thin, 32-mm open-end wrench to remove the cooling fan clutch.
3. Next turn over the engine by hand and line up the timing marks on the cam and the crank. Remove the crank pulley (you need an impact wrench for this) and the crank position sensor (depending on the year of your engine).
4. Remove the belt covers, upper and lower. Be careful when you remove and pull to the side the harnesses for the crank sensor and the oil pressure sensor.
5. Loosen the tensioner and slip off the belt.
6. If the tensioner pulley feels rough at all, replace it. Many people replace it with every other belt change.
7. Check the water pump for play and leakage. If there is any play at the snout of the pump, or any water present, replace it. Many people replace the water pump at this stage as a preventive measure.
8. Slip on the new belt, release the tensioner, and make sure that it takes up the slack without moving either pulley. Slowly rotate the engine by hand a couple times, checking that the marks stay aligned. Re-assemble the front of the engine and go for a test drive.