Very good advice. There is another consideration as well. Absolutely no liquid can get into any cylinder. Look up "diesel engine hydraulic lock".
Unless your head gasket failed as you pulled into the wash bay, no water from the car wash will affect anything hydraulically. Steaming hot water on a hot engine will not cause shock issues.
Sure you can douse the alternators and screw those up.
Put the nozzle of the high pressure spray right up to a connection or seal and push water into that causing issues.
Using ice cold water on a very hot engine "might" cause some thermal shock issues..... i.e. Exhaust manifold.
Been washing the engines of all my vehicles for 40 years.
Only one alternator failure and it was my fault.
Have washed countless Helicopter turbine engines with zero issues. Yes, pilots do wash aircraft.
Turbines are completely different animals but you get the point.
So, I will not worry about hydraulic lock.