Coolant does two jobs: it keeps the engine from freezing in winter and from boiling over in summer. Neglect it, and you risk cracked blocks, corroded liners, and clogged radiators. Here are four coolant checks that protect your engine year-round.
1. Test Freeze Point and Boil-over Protection
Coolant concentration matters. Too little antifreeze and the engine freezes. Too much and heat transfer drops, causing overheating. Use a refractometer (not a floating-ball tester) to measure concentration. The ideal mix is 50/50 antifreeze and distilled water for most climates, giving protection to about -37°C and boil-over protection to 129°C under pressure. In extreme cold (below -30°C), a 60/40 mix is acceptable. Never run straight antifreeze — it has poor heat transfer and can damage water pump seals.
2. Check Coolant Condition and Color
Fresh coolant is bright green, red, pink, or blue depending on the type. Old coolant turns brown, cloudy, or rusty. Cloudy coolant means oil or combustion gas contamination — check for head gasket or oil cooler leaks. Rusty color means the corrosion inhibitors are depleted and the system is rusting internally. If the coolant looks dirty, drain, flush, and refill with fresh coolant. Do not just top up — old coolant loses its protective additives over time.
3. Never Mix Incompatible Coolant Types
There are several coolant chemistries: IAT (green), OAT (orange/red), HOAT (yellow/pink), and others. Mixing different types causes gel formation, which blocks radiators and heater cores. Always use the coolant specified in your machine's manual. If you are unsure of what is in the system, drain it completely, flush with water, and refill with the correct type. Label the radiator or expansion tank with the coolant type used so the next service does not mix.
4. Inspect the Radiator Cap and Recovery Tank
The radiator cap holds system pressure, raising the boiling point. A faulty cap loses pressure, and coolant boils at a lower temperature. Inspect the cap seal for cracks or deformation. Have the cap pressure-tested — most systems run 50–100 kPa. Also check the coolant recovery tank. The level should be between "Low" and "Full" when the engine is cold. If the tank is empty but the radiator is full, the recovery hose may be blocked or the cap is not sealing.
Quick field check: Before starting on a cold morning, remove the radiator cap (only when cold) and look at the coolant. If you see oil film, rust flakes, or a muddy appearance, schedule a coolant flush. Also check the overflow hose — it should be clear, not cracked or clogged.
Want a coolant specification chart for your equipment? Reply with your machine models — we will send a PDF with recommended coolant types, change intervals, and a winterization checklist.
