This installment of Inside the Brands originally premiered in July 2015 and features CRP Brand Manager Paul Swyter discussing the aluminum stretch bolts used in selected BMW inline-6 engines.
In these engines, BMW was able to reduce the weight of the engine block 24% by using magnesium, resulting in better vehicle performance and fuel efficiency.
While magnesium is light and strong, it can have an electrochemical reaction with other materials such as iron. To prevent this from happening, BMW uses aluminum stretch bolts to mount different components to the block — such as the transmission, oil pan, water pump, and the alternator.
It is critical to note that these bolts are designed to be single-use only. Using the wrong bolt or re-using the existing bolts can result in improper torquing, or the bolts could loosen or break off in the block.
Rein Automotive offers a variety of replacement single-use torque-to-yield bolt kits for various BMW models from 2006-on: part # HWK0001 Manual Transmission Bolt Kit, HWK0002 Automatic Transmission Bolt Kit, HWK0003 Oil Pan Bolt Kit, HWK0004 Alternator Bolt Kit, HWK0005 Water Pump Bolt Kit, HWK0006 Oil Pan Bolt Kit, and HWK0007 Power Steering Pump Bolt Kit. For detailed application information, visit www.showmetheparts.com/crp.
Make sure you change out these one-time use aluminum bolts when you do a repair and use the exact torque specs we’ve included in each kit.
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