The GURU® DL2.1 CS and CHS may be thought of as an automatic freeze-out plug with one important difference: the stainless steel GURU Cartridge releases itself from its body at a preset water temperature (35°F or 40°F), rather than being forced out by the tremendous pressure of expanding ice.

This provides almost a full 1in bore to rapidly drain the typical compressor before damage can occur.

Resetting and rearming the GURU Plug is easily accomplished by simply reheating the cartridge and utilising our GURU Flag and Clip tool with slotted actuator feature. This feature prevents the GURU Plug from triggering open again while refilling the cooling system with cold water.

Benefits include:

  • Will not trip or dump while locomotive is running
  • Fully automatic, it never forgets to activate freeze protection
  • Completely mechanical, no electrical or air connections
  • Not affected by air flow or air temperature surrounding valve, releases only when cooling water reaches setpoint
  • Rapid draining
  • Easy system refill
  • Models available to convert existing freeze protection
  • Easily tested in field
  • Slotted actuator feature prevents nuisance dumps when refilling cooling system with cold water
  • Unit automatically rearms after filling and reheating

Design features:

  • Easily retrofits into water cooled air compressor heads
  • Flanged and 2in NPT threaded styles
  • Actuator sensing surface is the only wetted part
  • Long service life: all moving parts are stainless steel
  • Design excludes cooling water chemicals and other debris from moving parts
  • Easy maintenance
  • Paint mask minimises accidental paint-ins
  • Knob on cartridge for easy installation and removal even in awkward locations
  • Choice of release temperatures: 35°F or 40°F


  • Both are used for water cooled air compressor head freeze protection
  • The GURU CHS adapts to Gardner Denver’s compressor set cooling systems. Most common on EMD’s SD70 locomotives