Total War, page 38.
They're rare, but situations do exist where a mech can take damage during the End Phase of a turn. Most show up in TacOps, though Total War has some for IndustrialMechs.
Since the End Phase takes place after the Heat Phase, am I correct in assuming that a heat-related critical hit(damage to engines, heat sinks, anything else I've forgotten) does not actually affect the mech until the next turn's Heat Phase?