How to Keep Cool

If the cooling system is low, top it off. Use coolant, not water. Some beneficial properties of coolant over water are: It raises the boiling point; lowers the freezing point; inhibits rust and; lubricates the water pump. DO NOT use one size fits all coolant. Use only the coolant designed specifically for your vehicle. If you cross-mix coolants, they can create a gel. When that happens you have big problems. BE CAREFUL! There should be a manufacturer’s coolant information label somewhere under the hood. Use it. If not, get the owner’s manual from the glove box. If you don’t know which coolant to use or the proper coolant is not available, use distilled water. Do not use tap water if possible. We don’t want an adverse chemical reaction from fluoride, chlorine or whatever else is in the tap water and I certainly don’t want particles of iron circulating throughout the cooling system and grinding on things like plastic water pump impellers. By the way, the cooling system service intervals are listed on the label and in the owner’s manual. Service the cooling system on time. Coolant does wear out.

Many vehicles have cooling sys tems with the fill cap mounted on top of the expansion tank. If you inspect the expansion tank, you will see a cold and warm full mark. If the engine is warm, the coolant level in the expansion tank should be at the upper mark or warm level. In the morning when the coolant is cool, the coolant level should be at the lower mark, NOT THE TOP ONE. I don’t trust these systems to accurately display the correct coolant level. Look inside the radiator whenever possible. Here’s my explanation: When coolant temperature increases, the coolant expands into the expansion tank. When coolant temperature decreases and the coolant contracts, a vacuum is created in the cooling system drawing coolant out of the expansion tank and back into the cooling system. The radiator is ALWAYS FULL, hot or cold. But if the cooling system has a leak (not sealed), the expansion tank can lie. Outside air can be sucked into the cooling system instead of coolant from the tank. The unintended consequences are an air pocket in the cooling system and the expansion tank will always show full (TOP MARK) even if the system is cool and/or the Radiator is empty. If you verify the expansion tank level is active, then – and only then – can it be a trusted coolant level indicator.

Here’s some more overheating diagnostic tips I’ve learned over the years: If your vehicle overheats only when the vehicle is stopped or in stop and go traffic, suspect the radiator cooling fan is inactive. When traveling down the road the cooling system is not dependent on the cooling fan because air is being rammed through the radiator from the motion of the vehicle. When the vehicle stops, the rammed air also stops and the cooling system becomes dependent on the cooling fan. If the fan is inactive, overheating.

DIAGNOSTIC TIP #2: If the vehicle always overheats, happens within a few miles and the cooling system is full, suspect a stuck closed thermostat or head gasket failure. Unless the vehicle has been severely overheated within the last several months, the odds are in your favor it’s not a head gasket failure. If your cell phone has a forward-looking infrared app, sample the coolant temperature in front and back of the thermostat. If the thermostat is open the temperatures will be identical.

DIAGNOSTIC TIP #3: If the vehicle only overheats at higher speeds and/or climbing hills, suspect a restricted radiator or soft lower radiator hose. At lessor engine speeds, the engine generates less heat and the water pump turns slower. When the engine begins working harder it speeds up. As a result, more heat is generated and the water pump spins faster. If the radiator is internally restricted, not enough coolant can be circulated through the radiator to remove the increased heat. Also, if the lower hose becomes soft, the increased suction from the water pump can collapse it.