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Cooling Systems

By Jeff Zurschmeide

Imagine walking around wearing layers of long underwear, a sweatshirt, and a coat on a nice warm summer day. You can probably do it, but you won’t be comfortable because your body needs to shed heat. What’s the result? You huff and puff and can’t keep up the energy level you know you ought to have.

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.

Dos and Don'ts
Thumb up  DO
  • Change your coolant and flush your cooling system at least every other year
  • Have your radiator pressure-tested during your restoration process
  • Use the correct size radiator for your car
  • Have your radiator restored when your engine is restored
  • Use a qualified radiator shop to perform all your work

Thumb down  DON’T
  • Don’t use different types of coolant together
  • Don’t mix your coolant with too much, or not enough, water
  • Don’t re-use old coolant
  • Don’t let a radiator sit empty for long periods
The Popular Restorations Feature Car
Author photo

1946 Packard: Restoring the cooling system



The Popular Restorations feature car has an excellent cooling system. When I purchased the car I drove it 600 miles to Portland, Oregon. I had to go over two mountain passes in 98 to 100 degrees weather. Although the engine temperature went up to the high side of normal, it never overheated.

While restoring the car, I had the radiator boiled out and pressure tested and, fortunately, it was in excellent condition. Its longevity was probably due, in part, to its weight. When I say it is a heavy duty radiator, I mean I can barely lift it for fear of injuring my back. In fact I always ask for help.

Happily, now that everything is put together, it all works fine. It’s a good feeling knowing that the cooling system will probably not need serious attention for many years.



Mac's Radiator

By Jeff Zurschmeide

Brad Debray, Production and Custom Radiators
6147 SE Foster Road
Portland, OR 97206

PR: What is the process to recondition a radiator?

BD: If someone is doing a restoration, obviously they want to stay with original equipment. The cores are still available, depending on what it is. For example, if someone has a ’32 Ford, we can still get that core. If they brought in a 1917 Auburn, that core is very expensive, but it’s available. There’s pretty much nothing that’s not available. You can get pretty much anything if you go to the right people. I have different vendors out there who can make anything.

PR: People talk about having their radiators “boiled” and “rodded.” What do those terms mean?

BD: A boil-out tank is a hot tank with caustic fluid. If the radiator is 10-15% plugged, a boil-out tank will help, but it won’t get all of it. The only way to get it all out is to pull the radiator apart and run a rod through the tubes.

PR: How are these classic radiators made?

BD: They’re made of copper and brass, soldered together. If you’ve got a stock 1932 Ford radiator that has been taken care of, it can maybe take an overhaul. If it hasn’t been cared for, it will need a recore. A lot of times the tanks will start to decay. Even though they’re brass, they do get thin. Plus, a lot of those tanks were stamped, so they started with thinner metal to begin with. They didn’t need to be so thick because they weren’t using pressurized systems.

PR: Can you build a completely custom radiator to fit stock dimensions, or repair a severely damaged radiator?

BD: Yes. We have a full fabricating shop.

PR: How about maintenance?

BD: At least every other year or even annually, flush your system. Most people don’t do that. That’ll take care of replacing your anti-freeze. Most people think that once it’s mixed, you can leave it alone and it will be fine, but that’s not the case. Anti-freeze breaks down over time. And if you have a steel block and it sits for months on end, you need to start the car and bring it up to temperature every 3-4 weeks. Things will break down if you don’t.

PR: Is it a problem to leave coolant in a car being stored?

BD: Actually, it’s better to leave anti-freeze in a car. If you leave them dry, the radiator will dry out, oxidize, and the solder will crack.

PR: Do you recommend a particular coolant?

BD: They’re all pretty much the same. Stay away from “long-life” coolant. You can’t mix long-life with regular coolant. They don’t mix, but they become acidic.

Click on any item below for more details at Amazon.com

Ray T. Bohacz
Engine Cooling Systems
HP Trade, Paperback, 2007-11-06

This book is a guide to engine cooling systems for peak performance. It covers basic theory and modifications; individual components such as water pump, radiator, and thermostatic control systems; and information on designing a cooling system.

Randy Rundle
Automotive Cooling System Basics
Krause Publications, Paperback, 1999-02

This book explains cooling systems in an easy-to-understand manner. It includes 150 photos and numerous line sketches. The tech tips and project ideas will help readers identify and solve their cooling system problems, or even build a cooling system from scratch.

External Links
HowStuffWorks.com has a good article on How Cooling Systems Work.
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