The GURU® Valve DL2.1 CH 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 pre-set water temperature (35°F or 40°F), rather than being forced out by the tremendous pressure of expanding ice. This provides almost a full one-inch bore to rapidly drain the typical compressor before damage can occur.

The self-operating GURU® Valve DL2.1 CH and CHS continuously monitor and automatically respond to temperatures in the water-cooling system in diesel locomotives. If the water temperature falls to the valve’s set-point (either 35°F or 40°F/1.6°C or 4.4°C), the GURU® Plug will automatically snap open and drain the system before it can freeze.

Resetting and rearming the GURU® Plug is easily accomplished by simply reheating the cartridge and reinserting it into the hex nut. We recommend utilizing our GURU® Flag and Clip or GURU® Flag and Key tool during the refill process to prevent the GURU® Plug from triggering open by the cold water during the refill.

Typical Applications

These valves are designed for a diesel locomotive’s 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.

GURU® Valve CH Installed on Compressor

Design Features

  • Exclusive self-actuating Thermoloid® blend paraffin wax actuator
  • Thermal actuator sensing surface is the only wetted part
  • Easily retrofits into water cooled air compressor heads
  • Flanged and 2” NPT threaded styles
  • Long service life: All moving parts are stainless steel
  • Design excludes cooling water chemicals and other debris from moving parts
  • Paint mask minimizes accidental paint-ins
  • Knob on cartridge for easy installation and removal even in hard-to-reach locations
  • Choice of release temperatures: 35°F / 40°F


  • Self-operating – no external power source required
  • Will not trip or dump while locomotive is running
  • Not affected by airflow or air temperature surrounding valve
  • Rapid draining
  • Easy system refill
  • Easily maintained and tested in the field
  • Slotted actuator feature prevents nuisance dumps when refilling cooling system with cold water
  • Valve automatically rearms after filling and reheating
  • Optional domed anti-tamper cap eliminates ability to tamper with the valve resetting stem