Does anybody know where the power steering fluid reservoir is on the C63, the steering is making a slight high pitched rubbing type noise, it seems to be coming from the column inside the cabin, it's so trivial I can't be bothered to take it to the dealers and was wondering if it might be low on fluid but for the life of me I can't find any reservoir, I must be missing something because on the 2 year service schedule it states 'check steering fluid level'