The following article gives detailed instructions on replacing the drive belts in a BMW E63 6 series car with the N62 8 cylinder engine. Even though we have used a 2005 BMW 645ci to perform this installation, this article can be applied to any vehicle with the N62 8 cylinder engine with minor modifications.
A BMW E63 belt replacement should be performed at the first signs of wear on the accessory or AC drive belts.
Two of the most important components under the hood of your BMW 6 series vehicle, and often the least maintained, are the drive belts that power your engine’s mechanical accessories. The mechanical accessories include the water pump, alternator, power steering pump and air conditioning compressor.
The BMW N62 8 cylinder engine has two drive belts, both of which are driven by the crankcase pulley (harmonic balancer); the main accessory belt (also known as the “serpentine” belt) and the AC belt. The main accessory belt powers the water pump, alternator and power steering pump. The AC belt, as the name implies, powers the air conditioning compressor.
The two drive belts on your N62 8 cylinder engine are subjected to brutal conditions over the span of their lifetime. Extreme engine heat, pulley friction and stress take their toll on engine belts causing them stretch and crack. Oil leaks and other engine fluids can contaminate drive belts, weakening them and causing them to slip on the pulleys. A broken main accessory belt will shut down the water pump and power steering system, effectively making the car undriveable.
A BMW E63 belt replacement is a relatively simple repair for the home mechanic. It is important to note that on all 6 series vehicles produced from 2004-2010, BMW used a “stretch” AC belt to drive the air conditioning compressor. A stretch belt does not use mechanical tensioners, but rather is installed onto the AC pulley with a special tool (please see our tool list below for ordering). The stretch belt was also used on other BMW models with the N62 8 cylinder engine, including the E60 5 series and E65 7 series (production date from 10/2003). For those readers using this article to repair a model without a stretch belt, we have also included instructions for replacing an AC drive belt with the traditional mechanical tensioner pulley.
Many home mechanics with a stretch belt on their N62 engine have expressed interest in reverting to the mechanical tensioner system (stretch belt delete). It is a very easy and inexpensive switch to make. If you are interested in learning more about deleting your AC stretch belt and replacing it with a belt tensioner, please read our article BMW N62 AC Belt Tensioner Retrofit – Stretch Belt Delete before starting this repair.
1. Main accessory belt (required) – The main accessory belt powers the water pump, power steering pump and the alternator on the BMW N62 8 cylinder engine. The following are two quality choices based on personal preference and budget.
2. AC belt (required) – There are two different types of AC belts, depending on whether your vehicle uses a “stretch” or tensioner system. As a general rule of thumb, all BMW E60 5 series (8 cylinder), E63 6 series, and E65 7 series cars (production date from 10/2003) use a stretch belt. All early E65 7 series (production date to 10/2003) and E53 X5 4.4 vehicles use a belt tensioner system. Always visually check your engine before ordering to confirm which system you have.
- Jack and support the front of the vehicle. If you are not sure how to do this, please see our article BMW Jacking and Supporting for Repairs and Maintenance.
- Looking down inside the N62 engine compartment, identify the main accessory drive belt on the front of the motor.
- Use a small flat blade screwdriver or metal pick to remove the dust cap off of the tensioner pulley.
- Using a T50 torx bit and a long handle ratchet (or breaker bar), turn the tensioner pulley clockwise to release the pressure on the main accessory belt.
- With the tension released, remove the belt from the water pump pulley. Remove the belt from the engine compartment.
- Moving underneath the front of the car, identify the AC drive belt. It will either be a stretch belt or use a tensioner pulley, depending on the year of production and/or model of your vehicle.
- Stretch AC belts (belts with tensioner, see step 8) – Use a pair of heavy duty shears to cut the AC belt and remove it from the vehicle.
- AC belts with tensioner – Using a T60 torx bit, rotate the belt tensioner counter clockwise to release its pressure on the AC drive belt.Remove the AC belt from the pulleys.
Installing the new drive belts on models with a tensioner pulley is easy…just follow the above steps in reverse. Models with a stretch AC belt require several different steps. We show you both ways below. If you are interested in replacing your stretch AC belt with a tensioner system, please see our article BMW N62 AC Belt Tensioner Retrofit – Stretch Belt Delete before continuing.
- Stretch AC belts (belts with tensioner see step 2) – Loop the new AC belt around the crankshaft pulley (harmonic balancer). Partially install the belt on the bottom of the AC compressor pulley using the stretch belt installation tool to hold it in place (see image below). Using a long handled ratchet and a 24mm socket, slowly turn the crankshaft clockwise pulling the stretch belt onto the AC compressor pulley. Make sure to remove the stretch belt tool when you are finished. Check the belt to make sure it is aligned correctly on all pulleys…a misaligned belt can snap causing engine damage.
- AC belts with tensioner -Using a T60 torx bit, rotate the tensioner counterclockwise to retract the pulley. Loop the new AC belt around both the crankshaft pulley and the ac compressor pulley then release the pulley. Check the belt to make sure it is aligned correctly on all pulleys…a misaligned belt can snap causing engine damage.
- Install the new accessory belt, making sure it is routed correctly. Pay careful attention to where it loops around the power steering and deflection pulleys…this can be confusing.
- Using a T50 torx bit, turn the accessory belt tensioner clockwise retracting the pulley. Loop the accessory belt over the tensioner pulley then release it into its operational position.
- Check the belt to make sure it is seated correctly on all of the pulleys.
Always check, then double check, to make sure the belts are correctly lined up on the pulleys. A belt that is partially off of a pulley can snap causing engine damage. Start the vehicle and let it idle for a minute. Take the car for a spin around the block, then give the belts one more final check to make sure they are seated correctly on the pulleys.