The Guru® DL 2.1 thermostatic valves respond to engine coolant temperatures. When the locomotive is shut down and the cooling water temperature drops to the valve's set point, (Standard offerings: 35ºF or 40ºF) the valve cartridges will release, draining the locomotive cooling system before any freeze damage occurs.

After a drain occurrence, the valve cartridges can be heated and reinserted back into the hex nut to refill the water tank and promptly return the locomotive to service.