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.
1978 BMW 633CSi Automatic TransFACTORY OEM SERVICE PROCEDURE
Pressure Converter/Transmitter
- Start and run engine until normal operating temperature is reached. Ensure all vacuum hoses are connected properly.
- Disconnect Red hose from pressure transmitter and check for exhaust gas back-pressure at end of hose. If no pressure is felt, backpressure line or hose is leaking or plugged. Reconnect Red hose.
- Pull White hose from pressure transmitter and check for vacuum at end of hose. There should be vacuum. If not, check White hose and connections for leaks. Reconnect White hose.
- To check for control pressure on 630CSi, 633CSi and 733i, pull Red and Blue hoses from pressure transmitter. Vacuum should be felt at Blue hose fitting on transmitter. If not, replace pressure transmitter.
- To check for control pressure on 320i, disconnect Blue hose from pressure transmitter and check for vacuum at hose connection on transmitter. Vacuum should be felt. If not, replace pressure transmitter.
Factory Service Tools
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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.
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