Winter Car PrepThe Coolant Check Everyone Skips Before Winter
Weak coolant can freeze inside your engine and crack the block. A five-minute test in October is all it takes to know.
Everyone checks the tires and the battery before winter. Almost nobody checks the coolant. That's strange, because coolant failure in winter is one of the most expensive things that can happen to a car — a frozen engine block can crack, and a cracked block is a repair that costs more than many cars are worth. The test takes five minutes and a tool that costs a few dollars. Skipping it is a gamble with terrible odds.
Why it's wrong
Coolant — antifreeze — does two jobs: it stops the engine from overheating in summer, and it stops the water in the cooling system from freezing in winter. Over time, the mixture gets diluted: topping up with plain water, small leaks, and age all weaken it. Weak coolant freezes at a much higher temperature than proper coolant, and when coolant freezes inside an engine, it expands. That expansion cracks engine blocks, splits radiators, and bursts hoses. The other mistake is mixing coolant types — different colours and formulas don't always play together, and mixing the wrong ones can form sludge that clogs the cooling system. And never, ever open the radiator cap on a hot engine: the system is pressurised, and the coolant inside is hot enough to cause serious burns.
The right way
- Check the level in the overflow tank. With the engine cold, look at the translucent overflow reservoir — the level should sit between the MIN and MAX lines. If it's low, something is leaking or evaporating, and it needs looking into.
- Test the strength with a hydrometer or test strips. A coolant hydrometer costs a few dollars at any parts store. Squeeze a sample from the radiator or reservoir and read the freeze protection level. It should protect well below the coldest temperature your area sees.
- Top up with the right coolant, mixed correctly. Most cars use a 50/50 mix of coolant and distilled water. Pre-mixed coolant is the simplest option — no measuring, no mistakes. Use the type your owner's manual specifies.
- Look for leaks while you're there. Green, orange, or pink puddles under the car, a sweet smell from the engine bay, or white crust around hose connections all mean a leak. Fix it before winter, not during it.
- Know when a flush is due. Coolant doesn't last forever — the anti-corrosion additives wear out. Your owner's manual gives the interval. If the coolant looks rusty or murky, it's overdue.
- Only ever check with a cold engine. Wait until the engine has been off for hours before opening anything in the cooling system.
The rundown
Cold engine, check the level, test the strength, top up with the right mix, and watch for leaks. Five minutes in October protects the engine from the one winter failure that can total a car. If you're unsure which coolant your car needs, check your owner's manual — the type matters.