I agree with Rick that repair of this body after water damage just isn't practical given the low replacement cost because any proper repair will greatly exceed the cost of replacement. Cameras are both electronic and mechanical devices and any significant water entry has degraded the shutter/mirror mechanism in addition to any damage done to the electronics.
Very pure fresh water is the least damaging but people rarely drop their possessions into distilled water while even a heavy rain results in the oil/salt buildup from your skin working its way into camera bodies that aren't well sealed against weather and only Canon's most expensive series have that sort of weather sealing.
We live in a world where most consumer products are designed for replacement rather than repair even when the fault is relatively minor. Water into an unsealed consumer camera is not relatively minor.
Replacing a camera body that was functioning prior to moisture isn't a happy event but congratulate yourself on actually using your camera instead of leaving it sitting on a shelf as many people do. I use four 1DX II and III bodies and of the three, I purchased one of the two 1DX II bodies used. It was at a very good price and the prior owner apparently liked to see it sitting on a shelf because it was in pristine condition with a shutter count under 1,000 exposures (in a body rated for 400,000 before recommended replacement). Camera are meant to capture things to look at, not to be looked at sitting on a shelf.
Rodger
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
