Coolant in Winter

Coolant and Your Heater

Maintaining temperature inside your car in winter is critical and coolant plays a key part in keeping your heater working too. 

Your car uses coolant – usually made up of 50% antifreeze and 50% water – to cool your engine down, during the summer months. During the winter when you crank up your heat, the coolant is brought over from the engine to the heater core which then blows warm air into your car. This also helps maintain a clear windshield for visibility.

It can feel cool for the first few minutes because the engine has to warm up in order for the coolant to heat up and provide heat to your interior. If cool air continues to blow out, one of the main causes may be due low coolant, it won’t be able to send any to the heater core to create warm air.

Coolant Condition and PH

Coolant of good quality will be brightly colored. As coolant becomes old, it usually turns a brownish, rust colored liquid. At this point the coolant is past its useful life and must be changed. Coolant should be tested regularly to determine PH level and overall condition.
Ethylene glycol coolants can be tested with a hydrometer. The hydrometer uses floats to indicate the specific gravity of the fluid; you can read the level to find out if the coolant is still good.
Propylene glycol coolants may be tested with a paper test strip. The test strips are dipped into the coolant and then the color of the strip is matched to the chart to determine the condition. This method measures the pH of the liquid, an indication of the acidity level. When coolant becomes old it becomes acidic and can cause severe corrosion. Readings below pH 7.0 indicate that the coolant is acidic and should be changed.

Risks of Not Changing Coolant

Coolant can become more acidic over time and lose its rust-inhibiting properties, causing corrosion. Corrosion can damage the radiator, water pump, thermostat, heater core, radiator cap, hoses and other parts of the cooling system and can cause a car engine to overheat.


By getting rid of the scale and rust inside the radiator, heater core, and other components, it reduces the chances of radiator, thermostat, heater core, head gasket, and water pump damage, and lessens the chance of engine overheating, freezing, and or failing. It’s when this happens that you need to consider having your coolant flushed and cooling system inspected.

Coolant Flush Basics

Driving habits, the type of antifreeze you use, and extreme outside temperatures will help determine how often your radiator coolant needs to be flushed and exchanged for new. During a coolant flush, old antifreeze is pushed out, along with any contaminants that may harm your radiator, water pump, and other engine components. Once the rust is gone, along with the old antifreeze, you don’t want it coming back.


New coolant will be introduced into the system, which will contain additives that help prevent rust from forming on the inside of the radiator again. The water pump is lubricated by the additives in the new coolant and helps keep the water pump running longer and better, too. This simple maintenance step can greatly improve the life of your car and offers many benefits. A coolant flush often involves more than just flushing out old antifreeze. While your car is in the shop, your technician will pressure test the system to detect leaks and verify all components are performing as intended to prevent damage to your engine.

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