i steam clean them daily never had a problem if your worried wam up then refill oils if in runable vehicle , if units are on the floor seal up all openings ,including gear stick housing,blow off things like stater and alternator with air line,steam cleaner is better than cold wash as it dries quicker with been hot ,you can allways spray with paraffin or some detergent first,i would clean engine and g/box seperately so you can clean bellhousing and flywheel housing,