why is my BMW 5 Series G30/G31 (2017-2024) leaking transmission fluid?

Solution

1. Preparation

• Tools Required: Jack and jack stands, socket set, torque wrench, transmission fluid pump, drain pan, clean rags.
• Ensure the vehicle is on a flat surface and secure with jack stands.
• Allow the engine to cool down if it has been running.

2. Identify and Repair the Leak Source

A. Transmission Pan

• Sub-steps:
  1. Remove undercarriage protection if equipped.
  2. Loosen and remove the transmission pan bolts using a socket wrench.
  3. Carefully lower the pan and drain the old transmission fluid into a drain pan.
  4. Inspect the gasket for wear; replace if damaged.
  5. Clean the mating surface of the transmission and the pan.
  6. Apply a new gasket or sealant as required.
  7. Reattach the pan and torque bolts to manufacturer specifications (typically around 8-10 Nm).

B. Transmission Lines

• Sub-steps:
  1. Locate the transmission cooler lines and inspect for leaks.
  2. If leaks are found, use a wrench to loosen and remove the affected line.
  3. Replace the line with a new one, tightening to the manufacturer’s torque specification (usually around 20 Nm).
  4. Check for correct alignment to avoid future leaks.

C. Transmission Cooler

• Sub-steps:
  1. Inspect the cooler for external damage or loose fittings.
  2. Tighten any loose fittings securely.
  3. If damaged, remove and replace the cooler, ensuring proper attachment.

3. Refill Transmission Fluid

• Sub-steps:
  1. Using a transmission fluid pump, refill the transmission with the appropriate type of fluid (check owner’s manual for specifications).
  2. Start the engine and allow it to reach operating temperature.
  3. Check the fluid level with the dipstick and top off as necessary.