How do you replace tming belt on a 1990 BMW 525i?

Answer 1

Replacing the timing belt on this vehicle will take about 8 hours and will involve a lot of information found in a repair manual. If you don't have one I recommend the Bentley manual. You will need a good set of tools especially a torque wrench. Before you begin you will want to buy coolant, a new timing belt, a new timing belt tensioner and possibly a new water pump. BMW recommends you change the water pump every 120K miles and the timing belt every 60K miles. If you just bought the car I would suggest changing them both. You start by disconnecting the battery and draining the radiator. Remove the hood. Remove the radiator and hoses. Remove the belts to the AC compressor, Power Steering pump and alternator. Remove the clutch fan. Remove the metal coolant tube. Remove the distributor cap and rotor and the plastic cup behind the rotor. Remove the crank position sensor and the oil pressure sender. Carefully remove the wire holder on the front of the lower timing belt cover. Set the motor to TDC with the timing mark on the balancer. Use a chain wrench and remove the crankshaft pulley and the balancer without turning the crankshaft. Remove the upper and lower timing belt covers. Remove the old belt tensioner and dont lose the spring and plunger. Remove the timing belt without turning the crank or cam shafts. Now is time to replace the water pump. Use the torque specs from your manual when installing the bolts. Put the new belt on and align the marks on it with the marks on the cam and crank pulleys. It can be difficult to get the belt around the crankshaft because there's a metal cover below it and it's hard to see under the geared pulley. Clean under it as best you can to get any pieces of rubber from in the gears or the belt will never go on correctly. Once you feel you have the belt on correctly put the new tensioner on and torque to the specs in your manual then turn the crank clockwise 2 complete rotations and make sure the belt marks still align with the marks on the cam and crank pulleys. If not, take the belt and tensioner off and start again. When you do get the belt on correctly ( whew ) reinstall the lower and upper timing belt covers and reassemble everything in reverse order from there.

A couple of helpful hints 1) GET A MANUAL. 2) It is a good idea to change the front cam shaft seal and gasket since you are in there anyway. You will need a reverse star socket ( I think its 17mm but I'm not positive ) 3) Get the correct type of coolant - no phosphates. 4) You will need to burp the cooling system using the 8mm bolt on top of the thermostat housing, the procedure is in your manual. 5) Be super careful with the plastic wire holder that holds the cables to your crank position sensor and oil sender, it will be brittle and break easily. 6) When removing the hood mark the hood and mounts on the hinges so you can easily realign it when you put it back together. 7) It's up to you but on my personal car I cut the hose going to the windshield washer nozzles when removing the hood. Then put a plastic connector to reconnect the hose ends when I reinstalled the hood. Good luck with this project.