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.
Diverter Valve
The diverter valve prevents backfire in the exhaust system during sudden deceleration. The valve senses sudden increase in intake manifold vacuum, causing valve to open and allowing air from air pump to vent to the atmosphere. A pressure relief valve is incorporated into the diverter valve to prevent overloading the air pump.
On 633CSi and 733i, diverter valve operation is also controlled by an electromagnetic switching valve. The switching valve opens the diverter valve when engine speed exceeds 3750 RPM, this interrupts the air injection and vents the air to the atmosphere.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.