Newer Cars Don’t Breathe Through the Grilles
Question: More and more new cars have very small openings in the front to allow air to flow over the radiator. A few seem to have none at all. Does this cause a problem with overheating or do these new designs have some special way of cooling the engine?--D.R.
Answer: The move toward smaller grilles and radiator openings has come as designers have attempted to streamline cars and reduce air drag. The smaller openings, coupled with a thinner front profile, helps to get the air to glide over the surface of the car.
The task of supplying a steady flow of air to cool the radiator is handled by directing air up to the radiator from underneath the car. These cars are known as bottom breathers. They usually have a plastic scoop that directs air upwards.
Corvettes have been bottom-breathers for years. Some Chrysler vans have also used the bottom-breathing concept.
The radiator fan typically provides the cooling air for the radiator at speeds up to 25 to 30 m.p.h. Modern electric fans can regulate coolant temperature much more precisely than older belt-driven fans. At speeds above 30 m.p.h., air rushing into the engine from the movement of the car provides most of the cooling.
The bottom-breathing system may not supply as much fresh air as the older wide open grilles, but modern engines may not need as much cooling air. Newer aluminum radiators pass the heat more readily than copper radiators.
In addition, many manufacturers are using side tank radiators that are more efficient than top and bottom tank radiators. In side tank radiators, coolant flows horizontally, while the coolant flows vertically in top tank radiators.
Finally, engines run hotter nowadays, which improves engine efficiency and cut emissions. Exhaust components inside the engine block can run as high as 1,350 degrees and the spark plug as high as 1,500 degrees.
Engine coolant typically runs at 263 degrees under pressure, far higher than the boiling point of water and far higher than the temperatures typical only a few years ago.
