One of the routine maintenance items that you should perform on your BMW is the checking and replacement of your accessory drive belts. The belts are driven off of the crankshaft and power accessories such as the water pump, power steering pump, alternator and air conditioning compressor. There are typically two belts on the car – one that powers the air conditioning compressor and another that powers everything else. Both should be checked periodically (every 3,000 miles, or when you change your oil), and particular attention should be paid to the main belt. The car can run fine without the air conditioning belt installed.
Some of the early E30 cars use a standard v-belt design, and some of the later cars use what is known as a poly-ribbed belt. The poly-ribbed belt setup utilizes a spring-loaded belt tensioner pulley that provides the proper tension for the belt at all times, making adjustment unnecessary. The traditional style v-belts need to be tensioned using standard types of clamps and tensioners.
When inspecting your belts, the one thing that you want to look for is cracks. If you see any cracks at all, you should replace your belts. The cracks will usually occur on the inside of the belt. With the poly-ribbed belts, this is the grooved surface. With the v-belts, this is the surface on the legs of the ‘V’.
With the poly-ribbed belts, replacement is a snap. The tensioners that hold the belt tight can be easily released using a socket and or 8 mm hex tool. Different tensioners turn different directions, so you may have to rotate the tensioner clockwise or counter-clockwise depending upon your particular car. First, pry off the small plastic cap that covers the tensioner. Then, place your tool into the tensioner and try rotating clockwise or counter.
Removal of the two belts is next. Simply release the tension on the belt from the tensioner, and then the belt should simply slide off. Release the tension, and then you should be able to unwind the belt from the engine. The belt should be able to be maneuvered around and through the fan – you do not need to remove the fan to swap out any of the belts.
Installation of the new belt is easy. Simply slide on most of the new belt onto the pulleys, release the tension on the tensioner, and slide the belt onto the tensioner. Check to make sure that the belt is securely seated in all of the pulleys. Verify that the ribbed portion of the belt is set against the crankshaft pulley.
Replace any plastic caps that you may have removed from the front of the tensioner pulleys. Now, start the car and peek in at the belts. Verify that they are turning smoothly on all of the pulleys and you’re all set.