Cooling Systems

The U.S. Department of Transportation says cooling system failure is the leading cause of mechanical breakdowns on the highway...thus, what follows is definitely worth a few minutes of your time.

One Third – Two Thirds

As your engine consumes fuel, only about a third of the released energy goes into mechanical energy to run your car. The rest, fully two-thirds, is converted to heat. Some of that heat finds its way out of your car via your exhaust pipe, while the rest heats the engine itself (ever stick your face in the engine compartment on a hot day?). Your car’s cooling system is designed to accomplish one simple objective…remove excess heat from your engine.

Without a cooling system, the engine would be destroyed by heat within a half hour of startup.

The cooling system works by moving coolant (which is stored in the radiator) through the engine and then back through the radiator where its heat is transferred to the surrounding air thanks in part to the fan blowing through the radiator and in part to the forward motion of the car which drives air through the radiator. Some cars have electric fans (usually front wheel drive cars) while some are driven off the car’s engine (usually rear-wheel drive cars).


Coolant flow is regulated by a thermostatic valve or thermostat. This little device works to allow the engine to heat up quickly, and then keep the engine at a constant temperature. This is accomplished by regulating the amount of water that goes through the radiator. At low temperatures, the thermostat’s outlet to the radiator is completely blocked. In other words all of the coolant is re-circulated back through the engine.

Once the temperature of the coolant rises to between 180 and 195 F (82 - 91 C), the thermostat starts to open, allowing fluid to flow through the radiator. By the time the coolant reaches 200 to 218 F (93 - 103 C), the thermostat is open all the way.

Things to Watch Out For

Several conditions can arise in your cooling system which would put your car under a black cloud or at the business end of a tow truck:

Leaky radiators and hoses – this causes coolant to leak out and the engine to overheat. Overheated engines have a tendency to seize, freeze, warp and, in general, lock up. If this happens, may we suggest you find a place to sit down before you look at the repair bill?

Broken fan belts can essentially stop your engine cooling system in its tracks thus causing overheating as they prevent the water pump from circulating coolant and the fan from cooling the coolant.

Ethylene glycol, the main ingredient in most antifreeze, never wears out. What does wear out are the corrosion-inhibiting additives that protect the cooling system. Nor does the coolant remain clean forever. It picks up contaminants and byproducts of corrosion. The only way to get rid of the contaminants is to replace the coolant or filter and treat it on a regular basis.

Your cooling system relies on a water pump to circulate your engine’s antifreeze. It turns whenever your engine is running, so after a while, the bearing surfaces and seals get worn. When that happens, the pump can't turn freely, or it begins to leak coolant. That's when it's time to replace the water pump.

Coolant Expansion Tanks

The coolant expansion tank is connected to the cooling system (radiator) through a system of hoses. It provides for escape of pressurized gases and absorbs the coolant’s thermal expansion during rapid pressure buildup. It also prevents the coolant from boiling over when the hot engine is shut off.

How Not to Lose Your Cool

There are several steps you can do to help assure your cooling system operates properly. Pop your hood and look at the expansion tank every few weeks. Most have clearly visible lines showing where the coolant level should be – whether is the engine is hot or cold. Be prepared to add coolant if necessary.

Keep an eye on your dashboard temperature gauge. Regardless of whether its July or January, your gauge can be the first sign of trouble in a malfunctioing cooling system. And yes, cooling system failures can happen when the snow flies just as easily as when the sun shines.

Keep a record of when you last changed your anti-freeze. At Dallas Auto Sports, we recommend changing your coolant every 24,000 thousand miles or two years. This seems like a good place to remind you to also keep records of when you change oil and rotate your tires.

Dallas Auto Sports

As you’ve probably seen by now, your cooling system’s health is very important to the health (and longevity) of your car - especially in the middle of a hot Texas summer.

As you’ve probably also seen by now, it takes a fair amount of experience to diagnose and repair a modern car’s cooling system. We might add, a key part of this process is the anticipation factor.

We look at fan belts (which drive water pumps and cooling fan) and radiator hoses and the coolant itself and based on our experience, will counsel you on whether your car needs preventive maintenance or whether your system is in fine shape.

If you have concerns about the state of your cooling system, give us a call, stop by, or email us.

Dallas Auto Sports
8912 Garland Road
Dallas, Texas 75218

Mon. - Fri. 8 AM-5 PM

Auto service and repair for: Audi, BMW, Mercedes, Land Rover, Lexus, Jaguar, Porsche, VW, Volvo, Saab, and more. Servicing cars from the Dallas, Plano, Richardson and the DFW Metroplex area.