Steam Cleaning

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While changing a ball joint my mechanic noticed an oil leak on the lower part of the engine on my e46 318.
The problem is the oil is very spread and it is very difficult to make out where the oil leak is coming from. He recommended I would have the engine steam cleaned from underneath at a place that had some sort of ramp ( so can be cleaned underneath) and after run it for a week to see where the oil is coming from.
I have read a few articles regarding steam cleaning engines and I have to say I am a bit cautious so I was wondering if anybody had any thoughts regarding this.