Classic Car Cooling Problems

"My engine runs hot in the summer. Nothing I do seems to help. The engine was rebuilt perfectly and the antifreeze color is just fine. There's no rust or clogging in the radiator and hoses and the thermostat is a low temperature one. Why can't I get the engine to run cooler?"

I hear these words, or those very close to these, all the time from people driving old cars. Their cars tend to run hot during the summer months and it's frustrating. They think something is wrong with the cars when, as often as not, there really isn't.

Assuming your engine and cooling system are in as-built order, the reason your car tends to overheat is due to thermal efficiency - more to the point, the state of that art at the time your car was manufactured. Engines of previous eras were made of cast iron and radiators were copper, and bigger was better. If a car had sufficient room under the hood its radiator was huge, but if not the manufacturer would make it as large as possible and let the buyer worry about it.

Quite often this wasn't large enough. Engine blocks had massive amounts of cooling system flaws cast into them because there wasn't enough computer power in those days to properly design contours. Combustion chambers, intakes and exhausts were primitive (compared to today) and most of the fuel's explosive energy yielded heat. This heat had to be removed, just as it must today, but there was lots more of it in the older technology engines.

Today's engines get huge amounts of power out of relatively small displacements, which means they don't waste as much of the fuel as heat as your '56 Blunderbuss. That's why your modern cooling system can allow the car to sit idling indefinitely and won't overheat no matter how much you use the air conditioner. In fact, most cooling systems today can keep the operating temperature to plus/minus 5 degrees in all conditions.

Contrast that with your old car. Back in 19-whatever, nobody allowed their engines to idle for more than a few minutes and even police cruisers - when idling - kept their hoods up to aid cooling. Heavy traffic would quickly cause engines to overheat but, fortunately, the traffic of decades ago wasn't anything like it is today. The hard truth to the matter is; many cars run hot today because they ran hot when they were new!

How to solve the problem, you ask? Well, I put modern aluminum radiators into my restorations whenever possible. These radiators have about twice the BTU capacity as same-size copper radiators of yore. Our '55 T-Bird (these cars were famous for overheating, by the way) is fitted with one and so far our idling tests (20 minutes or more) have shown the engine temp to remain constant at about 180 degrees, and that's using a dinky electric fan drawing air through an A/C condenser and transmission cooler.

The downside is that you do compromise the originality, but our philosophy is that we want our restorations to be driven. You can frequently disguise a modern radiator to look like the old one, and if not, it's no big deal? You lose a few points at the show, but you get the advantage of being able to drive the car when you want, rather than when the conditions are acceptable.

I want to drive my old classic in summer and winter. I want air conditioning and heat, so as far as I'm concerned, whatever it takes to get there is worth the effort.