How to replace the serpentine belt on my 09 750li twin turbo BMW
Which engine is in it? Comment below and I'll try and find a diagram for it. First take lots of photos and notes before you start as reference for when you get stuck. (You will get stuck)! you might need to remove plastic guards, covers and some air intake pipes to gain access to some of the pulley wheels when putting the new one on. You will be working by feel only for some of this job so trace the route of the belt with your hand all the way around so you know where its supposed to go.
One of the pulleys the smooth side of the belt runs over is on a spring loaded tensioner arm. This needs to be swung against the spring to slacken the belt. Some engines have a slot or pair of holes you can line up and insert a pin to lock it in the 'slack' position. Again follow the belt around its whole length as you take it off to remind your self exactly where it goes. Fit the new one, this may take several attempts, and carefully release the tensioner.
A lot of companies recommend you change the tensioner as well. I agree as I've had one fail on me when my belt snapped. the tensioners just bolt into place and need to be fitted before you refit the new belt.
Once fitted, again trace it with your hand to check it is squarely set on all the pulley wheels, then start the car.
Then, KEEPING YOUR HANDS WELL CLEAR, look and check the belt is moving smoothly on all the pulleys you can see and not sliding from side to side. Check the dash board for any warning lights or messages and turn the engine off. Refit any pipes, guards and covers, recheck for any warning lights and messages on the dashboard and that should be job done!
BMW Cars &...
on Jun 03, 2020