Mark: the Sherman series had a variety of engine types so they had different ventilation, air intake (cooling) and exhaust configurations. The M4A3E2 (Jumbo) you discuss is plainly discussed by Robin. The rear deflector dealt with both engine exhaust and cooling air streams. No Shermans exhaust system was used to generate masking smoke. That's what smoke (white phosphorous) rounds and grenades were for.
Engine compartment heating was done by alternative duct work. And it did a somewhat adequate job.
I don't recall the height of normal crossings before special measures were needed to waterproof -- just say it's not comparable to today's standards. Maybe 3 feet? That's why bridging equipment or ferries were so necessary.