If you have a large sheet of polythene (of reasonable thickness/strength) it's worth putting that over the engine under the bonnet, then doing your car wash.
Helps prevent such, errr, embarassment?
My old X-flow doesn't have the problem...
Graham (G4FUJ)
Sold L44FOR 4/4 Giallo Fly '11 MINI Countryman Cooper D All4 '90 LR 90 SW