The objective of diesel engine coolant filters, also known as water filters, is to remove contaminants from the engine cooling system. Coolant filters can be of cartridge or spin-on design. However, spin-on designs are most common on today's diesel engine cooling systems. Coolant filters without chemicals, commonly called "Blank" coolant filters, should be used when a system is adequately charged and no additional SCAs are needed. The status of a cooling system can be determined using Baldwin's FleetStrip coolant test kit.