Stuart practices:
The reason fleets need to regularly pressure check on cooling systems and radiator caps at each PM is to avoid coolant loss and potential over-heating and shut-down issues. You need to pressurize the system to a minimum of 18 lbs. at each scheduled PM as well as the cap to its release pressure stamped on the cap. Be careful of replacement radiator caps; they should be checked before installation. There can be undetermined invisible coolant loss, as well as lower boiling points, and maybe film boiling.
Coolant can evaporate externally dripping on a hot engine -- these small amounts will escape undetected. If you are adding engine coolant at the fuel island, truck stop or in the shop, something is wrong. Make this simple procedural check a part of your preventive maintenance routine. When is the last time you added coolant to your own personal vehicle? After all, it is a closed system!
DWS Fleet Management website:
www.darrystuart.com