Since Viking engine cores originate from low mileage 2017 and 18 car engines, waterless coolant was not originally used. Engines are test run before leaving Viking but not long enough to remove all traces of moisture.
Because of this, engines must initially be run with an Evans prep fluid, before the NPG coolant is installed. The prep fluid will absorb any moisture and remove it from the engine block when drained. Since the latest Viking pressure cap is only at 4 psi (prior systems at 0 psi), boiling water in the engine will push coolant out and temperatures will fluctuate.
Engines can be updated to this latest standard by:
- Removing and drilling a small hole in the thermostat to provide constant air bleeding of the system
- Install the new coolant fill neck / 4 psi cap assembly to the engine.
- Run the Evans prep fluid during all ground operations, until ready for first flight.
- If NPG coolant has already been in contact with the internals of the engine, boil off any possible moisture and reinstall.
This will provide for a sound coolant system that is:
- Running low pressure
- Easy to fill
- Self purging
- Stable temperatures
