I have washed my 617 diesel while hot on several occasions, and nothing bad has happened...yet. Your post alarms me though, as the GM warning seems to make sense.
I really like to keep my car clean; inside, outside, underneath, and in the engine. It is so much easier and more pleasant to work on clean parts that arent caked in crud...but this injector cracking warning..
I never considered that. I will monitor this post to see if anyone has advice.