Well, your car works the same way. Your restored car needs to shed heat to work at maximum efficiency, but too often builders ignore the radiator. A clogged radiator looks pretty much the same as a working radiator from the outside. As long as it’s not dripping coolant on the ground, how can you tell?

Another pitfall is that most radiators have enough capacity to keep the car cool under easy conditions, but inevitably you’ll get caught in a long, slow climb up a hill on the hottest day of the summer, and that’s when your car will overheat. And that’s when you might damage your painstakingly restored engine.

Restoring your radiator takes just a little time and money, and it’s worth the investment to get the best possible job done. A modern radiator shop can clean your radiator’s passages with caustic baths, ultrasonic vibration, and by ramrodding the gunk out. If the heat dissipation vanes are crushed or the passages are just too worn, a professional shop can usually re-core your radiator for a fraction of the cost of a reproduction or NOS radiator. Along the way, they can paint or polish (or both) the tanks and give your radiator a proper pressure and efficiency test.

When you install your restored radiator in your car, don’t forget the other key components. These include the radiator cap, temperature sender, coolant hoses, and hose clamps. Make sure these at least appear to be period-correct for your car. Nothing spoils a perfectly restored engine bay like modern hose clamps.

But there are three additional pieces you can’t see that you’ll want to refresh--starting with your thermostat. The thermostat (assuming your car has one) is generally installed at one of junctions between your coolant hoses and the engine. It’s a valve that opens when exposed to hot water. This device helps your engine come up to operating temperature quickly, and then maintains the correct temperature while you’re driving.

The sneaky failure mode of thermostats is that over time, they don’t come open as much, limiting the flow of coolant to your radiator. Just like an inefficient radiator, you won’t notice the problem until the system is stressed. Ideally, you want your radiator to be capable of handling any conditions while the thermostat controls your engine’s operating temperature. You can test your thermostat by dropping it into a pan of boiling water on the kitchen stove.

The second hidden part is your heater core. This is just another radiator, and it’s subject to the same stresses as your primary radiator. Over time, the solder in your heater core, the valves that control coolant flow, the heater hoses, and the clamps can all degrade. If you smell coolant when you run your heat, chances are that your heater is at least weeping and needs to be restored or replaced. The best news is that if your core can’t be replaced with a correct part, at least it’s out of sight.

Finally, you’ll want to take your temperature sender and your water temperature gauge to a good gauge shop and have the two calibrated. Different gauges work in different ways, but the goal is that you should know when your coolant is operating at a safe temperature and what that temperature looks like on your particular gauge.

When you install your cooling system, be sure to fill your engine with modern coolant in the prescribed combination with clean (distilled, if possible) water. If you have an aluminum engine block, invest in a “sacrificial anode” to prevent the acids that develop in coolant from eating away at your engine block. The sacrificial anode is usually attached to a freeze plug or drain plug. It is simply a chunk of material that is designed to dissolve over time, neutralizing the electrochemical reaction between coolant and aluminum alloys.

If you make these simple small investments in your cooling system during the restoration process, you will be rewarded with reassuring gauge readings that you trust and a system that can handle whatever the summer driving and show season throws at you.