Antifreeze leaking out air dyer

My friend has 2002 Mack 300 the truck was idling and started smoking very minimal has never smoked before he got in the truck stepped on the accelerator pedal brought RPMS up motor sounded fine no issues the shut it off and notices antifreeze leaking out of the air dryer tries to start the truck up but it turns over then stops like it locked hydro lock. I don't think it is a head gasket because the truck ran fine until he shut it off no over heating or high temp oil is clean and not over full. I have never seen this happen before and have been around trucks over 40 years is it possible that the air compressor head gasket let go and is filling with fluid forcing it out the air dyer and also causing the motor to not turn over any and all help would be great.
thanks in advance John

Antifreeze leaking out air dyer