All about Automotive Cooling Systems

Submitted By: Kit Sullivan, Director of Training
Southern Express Lubes, Inc.

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GET THAT AIR MOVING!
Next, check the airflow-management system on your vehicle. What’s that, you say? It’s simply the fan, the fan shroud and any component that helps airflow travel across your radiator. At cruising speeds, most vehicles receive enough airflow across their radiators to provide sufficient cooling for their engine. If your car runs cool at cruise, but tends to overheat at idle, then there is probably insufficient airflow across the radiator at low speeds or idle. The cooling-fan is designed to provide that airflow at low and idle speeds. To make sure that they are giving you the best performance, there are a few things to check.

First, are the fan blades all present and accounted for? A fan that is missing blades causes an imbalance, reduces cooling and most importantly…is extremely dangerous! Make sure that your fan is in the right location to your fan shroud. According to ‘Griffin’, makers of excellent high quality radiators and other cooling system components, a fan needs to be no further away from the inside surface of a radiator than 2 inches. Any further away than that and the fan cannot create the air velocity needed for proper cooling.

Second, the outside diameter of the fan itself needs to be within ½” of the opening diameter of the fan shroud. A fan with a too-small diameter will ‘bleed’ pressure around the blades through the fan shroud opening, reducing airflow across your radiator. And the ideal spacing for the fan inside the shroud is for the blades to be as close to half inside, and half outside the fan shroud opening as possible. Sometimes, different combinations of fan shrouds, fan spacers and fans themselves can dramatically improve the performance of your cooling system.

Another area often overlooked on our older classic cruisers is how well the outside edges of the radiator are ‘sealed up’ to prevent air flow from ‘bleeding off’ the front of the radiator before it even has a chance to go through it.

The factory usually had many individual plastic ‘dams’, or block off plates that helped to direct the flow of air through the radiator. Some cars even have a tiny plastic ‘spoiler’ underneath the cross member whose sole function is to direct air up, and across the radiator.

If any, or all of these are missing, which can be common on a 30+ year-old car, your cooling system may not work as well as it was originally designed to.

Sometimes, adding an aftermarket fan may be your best bet. Whereas the factory may have installed a five blade fan, a six or eight bladed fan may give you the extra airflow that your cruiser needs.

And most factory installed fans are solid, fixed-pitch fans. This means that the blades are stiff and do not flex under operation.

An aftermarket flex-fan is designed with flexible blades that have a severe pitch to the blades, allowing for the maximum amount of airflow at low speeds, while at high speeds the flexible blades will ‘flatten-out’ somewhat reducing the high drag that a high-pitch fan would induce.
This helps to prevent the fan from ‘robbing’ horsepower from your engine at high r.p.m., which can be very significant.

Now while most fans are bolted directly to the front of the water-pump pulley, many vehicles came from the factory with a ‘fan-clutch’.

A fan clutch simply lets the fan ‘connect’ solidly to the pulley and provide maximum efficiency at low speeds, yet disconnects and allows the fan to ‘free-wheel’ at higher speeds when the fan is not needed.

These were provided to help quiet down the ‘whoosh’ that comes from a ‘full-time’ fan, while at the same time helping to increase fuel economy.
A fan clutch connects and disconnects based on temperature or r.p.m., depending on the specific application.

If your car is equipped with a fan clutch, make sure that it is in good working order. A fan clutch that fails to ‘engage’ when needed can cause a car to consistently overheat.
This one little device has caused many-a driver to scratch their heads, unable to figure out the problem with their cooling system.

Of course, electric fans are all the rage today, and almost every single new vehicle on the road uses one or a combination of them.

Many, many owners of older, classic cars have added electric fans to their cars to supplement the cooling on their vehicles.

Some have even removed the fixed-fans completely and replaced them with electric fans.
The idea is simple, and it works. At low speeds, when you need the maximum amount of fan speed to pull air across your radiator, an electric fan will operate at high r.p.m. At cruising speed, when there is sufficient airflow across your radiator, the electric fan ‘turns off’, and produces no horsepower robbing drag on your engine. Adding an electric fan to your pride and joy is a relatively simple and very effective way to help you, and your ‘baby’, keep your cool!

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