Yearly Service Update

Today I changed oil and filter in my Phaeton with a 3126 Cat engine. After the oil and filter change I thought I would clean my radiator from the engine side I shined a flashlight on the backside of the radiator which is hard to see through the fan blades but I could see dirt. I sprayed Simple green on the radiator core through the fan blades and waited about 10 to 15 minutes and started spraying the radiator through the fan blades but felt I was not doing good with the cleaning. I then had the bright idea of running the engine and then spraying the water through the moving fan blades. All went good for a couple of minutes and then I started getting a slapping noise from the fan shroud so I turned off the engine and tried to see what stupid thing I did. I couldn't see anything The serpentine belt seemed okay and other belts seemed okay. I restarted the engine and noise for just a second and then cleared up. Later when I moved the motorhome off of the ramps I picked up the revs to about 1500 and then minimum slapping noise and cleared up, I drove the motorhome down the street turned it around an re parked it in the driveway with no noise. After thinking about the slapping noise I think that when I was spraying the water the fan shroud collected water in it and the fan blades were hitting the water in the shroud. Does anyone agree with my thinking or have I done some serious damage?