@yen_susheel : IMO i dont prefer washing engine bay with water. Especially with power wash. in fact Volkswagen suggests not to wash engine bay with water. But if you still prefer to wash these are the few points to be taken care of: 1. The best time to detail your engine is in the morning when it has been sitting all night. If you throw cold water on a hot engine then you run a much higher risk of causing damage. 2. Before you begin detailing, cover the battery, any exposed filters, and the engine's air intake. 3. always use a gentle stream of water. avoid the power wash 4. there are many engine degreaser available , take a look at them.