BMW’s use of single-use aluminum stretch bolts isn’t a cost-cutting move. It’s a design decision, and reusing them can cause real problems.
In this Inside the Brands episode, Rein Automotive Brand Manager Paul Swyter explains why BMW uses one-time-use aluminum stretch bolts on many modern engines and why they must be replaced during service.
BMW’s 3.0L inline-six aluminum-magnesium engine blocks reduce weight and improve performance, but magnesium can react electrochemically with other metals. To prevent that, BMW uses aluminum stretch bolts to attach components such as the transmission, oil pan, alternator, and water pump.
Reusing these bolts or installing the wrong hardware can lead to improper torque, bolts backing out, or bolts breaking off in the block. Any of those issues can turn a routine repair into a much bigger problem.
This video covers why aluminum stretch bolts are single-use.
What can go wrong if they’re reused.
Why correct torque specs matter on BMW aluminum-magnesium blocks.
Rein Automotive offers hardware kits with the correct single-use aluminum stretch bolts for many BMW applications from 2006 and newer. Each kit includes the proper bolts and torque specifications for the repair.
Available Rein hardware kits include:
HWK0001
BMW 1 Series 2008–13, 3 Series 2007–13, 5 Series 2008–13, Z4 2009–13
HWK0002
BMW 1 Series 2008–13, 3 Series 2006–13, 5 Series 2006–11, X3 2007–12, X5 2007–10, Z4 2006–11
HWK0003
BMW 1 Series 2008–13, 3 Series 2006–13, 4 Series 2014, 5 Series 2006–11, 7 Series 2011–14, M235i 2014, X5 2007–14, X6 2008–13, Z4 2006–14
HWK0004
BMW 1 Series 2008–13, 3 Series 2006–13, 5 Series 2006–11, X3 2007–12, X5 2007–10, Z4 2006–11
HWK0005
BMW 1 Series 2008–13, 3 Series 2006–13, 5 Series 2006–11, X3 2007–12, X5 2007–10, X6 2008–10, Z4 2006–11
HWK0006
BMW 1 Series 2008–13, 3 Series 2006–13, Z4 2006–11
HWK0007
BMW 1 Series 2008–13, 3 Series 2006–13, 5 Series 2006–10, X3 2007–10, X5 2007–10
If you work on BMW engines regularly, replacing these bolts is a small step that helps prevent much bigger headaches later.