The following article gives detailed instructions on replacing the drive belt tensioner and deflection pulleys 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 pulley replacement will eliminate the squeaking sound coming from your 8 cylinder N62 engine while it is idling.
There is nothing else quite as annoying as the subtle squeaking sound from old belt pulleys. A failing belt tensioner or deflection pulley has a distinct tone; it’s a high pitched squeak that is most noticeable when the engine is idling. The irritating sounds quickly disappear as the engine’s rpm’s increase, only to reemerge when the vehicle rolls to a stop.
A BMW E63 pulley replacement is a simple repair that will immediately eliminate the obnoxious idle squeal from under the hood of your 2004-2010 6 series car (or any other vehicle with the N62 8 cylinder engine). It involves replacing the belt tensioner and deflection pulley on the main accessory (serpentine) belt on the front of the engine. If you are repairing an E65 7 series with a production date before 10/2003, or an E53 X5, it also includes replacing the belt tensioner on the AC drive belt (all other N62 engines have a “stretch” belt that does not have a tensioner pulley).
The main accessory belt is powered by the crankshaft pulley and drives the vehicle’s water pump, power steering pump and alternator. The tensioner and deflection pulleys help guide the accessory belt, applying the correct amount of pressure so it doesn’t slip or break. As the tensioner and deflection pulleys begin to age, their internal bearings start to fail emitting an annoying squeak. The pulleys should be replaced as soon as possible at the first signs of wear. A failed pulley can seize up precipitating the accessory belt to break and possibly causing catastrophic engine damage.
A BMW E63 pulley replacement is a simple repair, even for the beginner home mechanic. It can be done completely from the engine compartment without the need to jack the front end of the vehicle.
Please note that on certain BMW models, the N62 8 cylinder engine also had a tensioner pulley on the air conditioning (ac) drive belt. These models include the E65 745i (production date to 10/2003) and E53 X5 , as well as certain 5 and 6 series European spec vehicles. All other N62 engines (including the one used in this repair) do not have a tensioner pulley on the AC drive belt; instead they use a “stretch” belt that requires a special procedure to replace. If your vehicle has a tensioner pulley on the AC drive belt, then it also must be replaced during this repair. For more information on stretch belts and retrofitting your stretch AC drive belt with a belt tensioner system, please see our article BMW N62 AC Belt Tensioner Retrofit – Stretch Belt Delete.
1. Tensioner pulley (accessory drive) (required) – The tensioner pulley is a one piece unit that includes the pulley and its spring loaded tensioner mechanism. We give you several quality choices based on your personal brand preference and budget.
2. Deflection pulley (required) – Always replace the deflection pulley when doing this repair. It is as important as the tensioner pulley and is a major source of engine squeak when it starts to fail.
3. Tensioner pulley (AC drive) (may be required) – If you are using this article to repair your E65 7 series with a production date before 10/2003, or an E53 X5 4.4, then you will also need to purchase an AC drive tensioner pulley. Both choices are high quality replacement parts at a reasonable price.
4. Tensioner pulley mounting bolt (optional) – Although not required, it is highly recommended that you replace the tensioner mounting bolt on older model vehicles. A new mounting bolt is cheap insurance against future tensioner failure. It is recommended that you only use Genuine BMW factory bolts on your vehicle.
5. Accessory drive belt (optional) – Since you will need to remove the main accessory drive belt to complete this repair, now is a great time to replace it.
6. AC drive belt (optional) – Once again, if you are using this article to repair your E65 7 series with a production date before 10/2003, or an E53 X5 4.4, now is a great time to replace your AC drive belt since it will have to be removed for this repair.
- 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.
- Use a 16mm socket wrench to remove the belt tensioner mounting bolt. Remove the belt tensioner from the engine.
- Locate the deflection pulley – it is located near the bottom of the engine next to the alternator. Use a flat blade screwdriver of metal pick to remove its dust cover.
- Use a T50 torx bit and a long handle wrench or breaker bar to remove the deflection pulley from the engine.
Optional steps: If you are repairing a pre 10/2003 BMW E65 7 series or E80 X5 with an N62 8 cylinder engine, or if you have have an N62 engine with a retrofitted ac drive belt tensioner, then you will need to remove the ac belt tensioner pulley. If you do not have one of these vehicles, proceed to Section 2 below.
- 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.
- Identify the ac drive belt tensioner on the bottom front of the engine.
- Using a T60 torx bit, rotate the belt tensioner counter clockwise to release its pressure on the AC drive belt.
- Remove the AC drive belt from the air compressor and crankshaft pulleys.
- Use a 16mm socket wrench to remove the AC tensioner mounting bolt. Remove the tensioner from the vehicle.
Installing the new pulleys is very simple…it is just the reverse of the above repair steps. Note that newer tensioners may use a T60 torx bit to retract the pulley instead of a T50. It is critical that you use the correct torque on the mounting bolts to avoid premature pulley failure. Over torquing a bolt can be as serious as under torquing; we give you the correct torque specifications below for your convenience.
- If you are repairing a BMW vehicle with an N62 engine that has an AC belt tensioner, install the new tensioner now. Torque the mounting bolt to 47 Nm (34 ft-lb).
- Install the AC drive belt, making sure it is properly looped over the two pulleys. Note that the new tensioner comes “pre-loaded” in the open position with a lock pin installed. In order to remove the lock pin, slightly turn the tensioner counter-clockwise and remove the pin (watch your fingers). Release the pulley into its operational position. Double check to make sure the belt is properly lined up on the pulleys.
- Moving back to the top of the engine compartment, install the new deflection pulley. Torque its mounting bolt to 47 Nm (34 ft-lb) and replace its dust cap.
- Install the new accessory belt tensioner pulley and hand tighten the mounting bolt. Note that the tensioner comes pre-loaded in the open position with a locking pin.
- Torque the accessory belt tensioner mounting bolt to 47 Nm (34 ft-lb).
- Use a T60 torx bit to turn the tensioner clockwise just enough to release pressure on the locking pin. Remove the locking pin from the tensioner.
- Reinstall the 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 T60 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.