BMW Crankshaft Bolt 11-21-1-720-633

BMW part number 11-21-1-720-633 is a crankshaft bolt for BMW M50 / M52 / S50 / S52 and M54 engines. This bolt is used to secure the crankshaft pulley or harmonic balancer to the crankshaft, ensuring proper alignment and rotation of the crankshaft and accessory drive components.

When and Why to Replace BMW Part #11-21-1-720-633:

1. Routine Maintenance or Engine Overhaul

• During a major engine rebuild or overhaul, all critical fasteners should be replaced to ensure the engine operates reliably, as bolts can stretch or weaken over time.

2. Signs of Wear or Damage

• Visible wear, corrosion, or thread damage on the bolt.
• Loss of torque retention due to stretching or over-tightening during previous installations.

3. Upgraded or High-Performance Applications

• Customers modifying their engines for forced induction or high-performance use may replace stock crankshaft bolts with upgraded fasteners for better strength and reliability under increased stress.

4. Crankshaft Pulley or Harmonic Balancer Replacement

• Replacing the harmonic balancer, crankshaft pulley, or timing gear often necessitates removing the crankshaft bolt. Since some bolts are torque-to-yield (TTY) and stretch upon installation, they must be replaced rather than reused.

5. Preventative Measures

• Enthusiasts and professionals may replace crankshaft bolts as a precautionary measure to avoid potential failures that could lead to catastrophic engine damage, especially in older or high-mileage engines.

BMW M50 Applications:

3 Series

1990-1995     E36     320i / 325i / 325is
1994-1996     E35/E36     318ti

5 Series

1990-1996     E34     520i / 525i
1991-1996     E34 Touring     520i / 525i

Z Series

1995     E36/E37     Z3 2.0i / 2.5i

BMW M52 Applications:

3 Series

1994-1999     E36     320i / 323i / 323is / 328i / 328is
1997-2000     E35/E36     318ti / 323ti

5 Series

1996-1998     E39     520i / 523i / 528i

7 Series

1996-1998     E38     728i / 728iL

Z Series

1996-1999     E36/E37/E38     Z3 2.0i / 2.2i / 2.8i

BMW S50 US Applications:

3 Series

1994-1995     E36     M3

BMW S52 Applications:

3 Series

1996-1999     E36     M3

Z Series

1998-2000     E36/E37/E38     Z3M

BMW M54 Applications:

BMW 3 Series

2000-2006     E46     320i / 320Ci
2000-2006     E46     325i / 325xi / 325Ci
2000-2006     E46     330i / 330xi / 330Ci

BMW 5 Series

2000-2003     E39     520i [Europe]
2000-2003     E39     525i 
2000-2003     E39     530i

2003-2005     E60/E61     525i
2003-2005     E60/E61     530i

BMW 7 Series

2001     E38     730i / 730Li [Europe]

BMW Z3 Series

2000-2002     Z3     2.2i / 2.5i / 3.0i

BMW Z4 Series

2002-2005     Z4     2.5i / 3.0i

BMW X3 Series

2003-2006     E83     X3 2.5i / 3.0i

BMW X5 Series

2000-2006     E53     X5 3.0i