Power Steering Squealing & locking up

i own a 2005 Cadillac Deville. Only when it has rained this issue arises. if i pull thru a water puddle with the right front tire. even at a stop sign. my steering locks up. it squeals LOUDLY, and it takes everything ive got to turn my steering wheel to get it to unlock. it wont do it for my mechanics. (of course) all belts and pullys look good and are tight, fluid is in PS pump. i just dont know what else to get them to check. This is very dangerous. i need some help. any suggestions.

Clearly, the belt that drives the PS pump is slipping.
Either the belt tension is not correct, or the belt is glazed, or…and this may be a bit of a stretch…there is a missing splash shield underneath the car.

Car manufacturers place splash shields in strategic places in order to prevent problems such as you are experiencing. If the car has ever been in an accident, or if you ever drove over some debris that caused damage underneath the car, that could account for a missing splash shield.

Since this appears to be beyond the expertise of your regular mechanic, I suggest that you bring the car to a different mechanic. This is not rocket science.

thank you. i will get it back into a shop for further repairs. I really appreciate this expertise. this is just to dangerous to drive like this.