The coolant filter cleans the liquid in the engine cooling circuit of corrosion products, scale deposits and sealant particles. In large diesel engines — especially in construction machines, generators and trucks — the coolant filter also acts as a dispenser for corrosion inhibitors (SCA/DCA) that protect wet cylinder liners against cavitation corrosion.
Coolant filters available at Filtry.org from HIFI Filter, SF Filter and PZL Sedziszow include versions with SCA (Supplemental Coolant Additive) and without, filtering particles from 40 um. They fit Caterpillar, Cummins, Detroit Diesel, John Deere and Komatsu engines.
Piston vibrations cause rapid pressure changes in coolant at the liner wall, forming and collapsing vapour bubbles. The implosions tear out microscopic metal fragments, creating characteristic craters. SCA inhibitors form a protective layer on the liner surface, preventing this phenomenon.
Use an SCA filter at the first change after filling the system with fresh coolant. Subsequent filter changes should use non-SCA filters unless coolant analysis shows inhibitor levels are too low. Excess SCA can cause deposit precipitation and reduced heat transfer.
Every 250-500 engine hours or every 15,000-30,000 km in heavy trucks. Engine manufacturers specify exact intervals in the service manual. It is practical to combine coolant filter changes with oil filter changes.
Most passenger cars do not have a separate coolant filter. They are used mainly in large diesel engines with wet cylinder liners (trucks, construction machines, generators). In passenger cars regular coolant replacement every 2-5 years is sufficient.