With the Heat Sink Coolant Failure option (Tactical Operations, pg 105, Corrected second printing, old omnibus version) it's possible for hot units to reduce their heatsinking ability below their current heat level. At some point this can leave a Mech unable to effectively reduce it's heat at all. Does this constitute being 'crippled' for forced withdrawal (Total Warfare, pg 258, Corrected fifth printing)?
For example, a classic GR-1N Griffin has 12 single heatsinks. Due to repeated coolant failures it can now only dissipate 5 heat. If it has an engine hit it cannot reduce it's heat level even if it stands still and does not fire any weapons. If the current heat is 5 or higher it may continue to loose capacity each round. Under Total Warfare the single engine hit does not make it crippled, even though it would be practical to withdraw at that point (and perhaps before) before it shuts down.
