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If you own an M57-equipped BMW, you already know this twin-turbo diesel powerplant is an absolute torque monster. What you might also know is that all that low-end grunt and high-compression diesel vibration wreaks absolute havoc on your accessory drive system.
From the factory, both the E90 335d and E70 X5 35d utilize a rigid alternator pulley. With each cylinder's fire, the crankshaft experiences a violent micro-acceleration. Because the alternator has a heavy internal rotor spinning at high speeds, it wants to keep spinning at a constant rate. When the engine suddenly slows down (even minutely between firing cycles), the alternator fights the belt. This constant tug-of-war results in extreme stress on your engine's belt-driven components. At best, it’s an annoying, unrefined chirp at idle; at worst, it’s a ticking time bomb for your expensive harmonic balancer.
To solve this issue, many enthusiasts choose to run a clutched alternator pulley (also called an overrunning alternator pulley). A clutched pulley allows the alternator to "freewheel" or coast when the engine slows down, completely isolating its rotational inertia from the belt drive to prevent component wear. While the N52's clutched pulley (12317560483) is a straight bolt-on, the offset is incorrect for the E70 35d's accessory drive. Thankfully, our engineers designed this zinc-coated spacer to provide the precise amount of spacing needed to perfectly align the new pulley with existing belt drive components.
If you own an M57-equipped BMW, you already know this twin-turbo diesel powerplant is an absolute torque monster. What you might also know is that all that low-end grunt and high-compression diesel vibration wreaks absolute havoc on your accessory drive system.
From the factory, both the E90 335d and E70 X5 35d utilize a rigid alternator pulley. With each cylinder's fire, the crankshaft experiences a violent micro-acceleration. Because the alternator has a heavy internal rotor spinning at high speeds, it wants to keep spinning at a constant rate. When the engine suddenly slows down (even minutely between firing cycles), the alternator fights the belt. This constant tug-of-war results in extreme stress on your engine's belt-driven components. At best, it’s an annoying, unrefined chirp at idle; at worst, it’s a ticking time bomb for your expensive harmonic balancer.
To solve this issue, many enthusiasts choose to run a clutched alternator pulley (also called an overrunning alternator pulley). A clutched pulley allows the alternator to "freewheel" or coast when the engine slows down, completely isolating its rotational inertia from the belt drive to prevent component wear. While the N52's clutched pulley (12317560483) is a straight bolt-on, the offset is incorrect for the E70 X5 35d's accessory drive. Thankfully, our engineers designed this zinc-coated spacer to provide the precise amount of spacing needed to perfectly align the new pulley with existing belt drive components.
This product was last offered at the strikethrough price on
05-03-2026
This product was last offered at the strikethrough price on
05-03-2026
Upgrade your stock oil cooler thermostat for improved performance. Swap your factory 110-degree Celsius thermostat for a new 70-degree Celsius version for faster oil flow and extended temperature control. With oil temperatures reaching 230 degrees Fahrenheit by the time your factory thermostat opens, initiating oil flow at lower temperatures proves more effective than attempting to cool down already elevated temperatures.
Utilizing a factory-style thermostat, this upgrade can be used in all weather conditions and allows your engine to warm up properly, unlike thermostat bypass kits.
Kit contents:
Lower temperature thermostat - 70c (158F) vs Factory 110c (230F)
Low temp thermostat spring
This product was last offered at the strikethrough price on
05-15-2026
This product was last offered at the strikethrough price on
05-03-2026
This product was last offered at the strikethrough price on
05-03-2026
This product was last offered at the strikethrough price on
05-03-2026
This product was last offered at the strikethrough price on
05-03-2026
This product was last offered at the strikethrough price on
05-03-2026
This product was last offered at the strikethrough price on
05-03-2026
