Technical Service Bulletins - Engine - High Pressure Steam Cleaning Warning -Group 12 Engine – Electrical Bulletin Number 12 03 89 (1838) Woodcliff Lake, NJ March 1989, Technical Dept.
SUBJECT: High Pressure Engine Steam Cleaning, MODELS: All
Situation: High pressure engine steam cleaning can force cleaning solutions into the engine harness sheath and associated cables, causing unusual problems which otherwise would not have occurred.
The high quality BMW engine harness multiplugs and related sealing measures were never intended to be subjected to the discharge velocity and force of typical commercial steam cleaning units. Further, cleaning solutions used in conjunction with the high pressure discharge can leave corrosive, if not conductive, residues deep within the harness and cables.BMW engines are rarely so encrusted with automotive residues and dirt that normal low pressure degreasing methods fail to provide proper, efficient cleaning.
Clearly, high pressure engine steam cleaning is unnecessary and should be restricted to extreme cleaning jobs, i.e., commercial trucks, off road vehicles, etc
CONSEQUENTLY HIGH PRESSURE ENGINE STEAM CLEANING IS EXPRESSLY PROHIBITED FOR BMW ENGINES.
Typical BMW engine washing procedure:
1. Bring engine to operating temperature, switch engine off.
2. Cover or shield any component (AFM, ignition distributor, multiplugs etc.) situated in the area to be cleaned with plastic sheeting. Pieces of a "BMW Clean Kit" seat cover or the equivalent will provide adequate protection.
3. Apply engine degreaser or general engine cleaning solvent and allow to soak for up to five minutes (follow manufacturer's instructions).
4. Warm water spray the area to be cleaned, flushing the solvent and the contaminants loose.
Note:
- Do not aim the water spray directly at components.
- Do not use the waterspray any longer than necessary.
- Do not wash the entire engine compartment when only one area requires degreasing, e.g., front crankshaft radial seal, M20 oil filter replacement,etc.
5. Blow dry the cleaned area immediately with a moderate compressed air jet.
6. Start engine immediately and preferably road test vehicle.

Uebersetzt ist es Hochdruckdampfreiniger. Aber ich nehme nie einen Hochdruckreiniger fuer den Motorraum. Ich mach es genau nach Anleitung:
Typical BMW engine washing procedure:
1. Bring engine to operating temperature, switch engine off.
2. Cover or shield any component (AFM, ignition distributor, multiplugs etc.) situated in the area to be cleaned with plastic sheeting. Pieces of a "BMW Clean Kit" seat cover or the equivalent will provide adequate protection.
3. Apply engine degreaser or general engine cleaning solvent and allow to soak for up to five minutes (follow manufacturer's instructions).
4. Warm water spray the area to be cleaned, flushing the solvent and the contaminants loose.
Note:
- Do not aim the water spray directly at components.
- Do not use the waterspray any longer than necessary.
- Do not wash the entire engine compartment when only one area requires degreasing, e.g., front crankshaft radial seal, M20 oil filter replacement,etc.
5. Blow dry the cleaned area immediately with a moderate compressed air jet.
6. Start engine immediately and preferably road test vehicle.