Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel Tank Leakage: Notes
2000 BMW 740iLSECTION Notes
NOTE:
If a leak in the tank ventilation system is indicated by CHECK ENGINE light in instrument cluster lighting up, a leak test must be carried out. Fault memory of DME control unit must be read out using BMW or generic scan tool. If sensors are okay, then begin leak test. Ensure following conditions are observed to obtain plausible measuring results:
- Contents of fuel tank: 25-75% full.
- Park vehicle at least 2 hours before test so fuel temperature is approximately that of ambient temperature. Ideal fuel temperature is approximately 50-68°F (10-20°C).
- Never refuel vehicle directly prior to leak test due to strong emission of gas by fresh fuel.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.