DG96

The first 2500 Model T's came with water pumps. After those first 1909 cars, the next 15,004,533 Model T Fords came from the factory with no water pump. Why no pump? The Ford thermosyphon cooling system was designed to run without it. Heat rises. Cold sinks. As water (or coolant) is heated in the engine's water passages, it becomes less dense (lighter) and rises up through the hose into the radiator's top tank. As water in the radiator is cooled, it becomes more dense (heavier) and sinks. Over half of the water in the radiator is above the level of the engine's water passages, and its weight pushes that cooler water at the bottom up through the pipe and back into the engine where it's again heated and rises into the tank, and on and on.

Before we get into the question of what to do about overheating let's ask: Is that really what's happening? Typically a new Model T owner will fill the radiator, drive the car, and find that pretty soon coolant is spurting out of the overflow. This is because as the coolant heats up it expands, and if the radiator has been filled to the top the only place for the expanded coolant to go is out through the overflow pipe. This is not overheating. If it's followed by boiling, THAT is overheating. When you "fill" the radiator, put in enough coolant to cover the tops of the tubes. Some folks go up to the Ford logo. Don't bring the level all the way up to the neck. If the system is working as it should, the coolant won't reach the boiling point. When you shut off the engine, if you hear gurgling for a few seconds, that's not boiling. If you hear seething and see steam, that's boiling and you have an overheating problem to fix.

Before getting into cooling system troubles that you need to fix, we should be sure that overheating isn't caused by something else: driving style. Driving with the spark lever too high (retarded) can do it. Running too retarded can also be the result of incorrect timer setting. To check for that, see How to Set Timing. Driving with the carburetor adjustment too lean can also raise the heat level, especially when it's combined with the timing set too retarded.

Why does a radiator quit cooling as it should? One reason is accumulated foreign matter in the radiator and water passages that (1) interferes with circulation and (2) keeps the coolant from making direct contact with the heated cast iron of the block and the cooling tubes of the radiator. This is why it's important to use a good anti-freeze or rust inhibitor even in climates without freezing weather. Modern antifreezes contain rust inhibitors to prevent corrosion. Antifreeze is normally mixed 50/50 with water. You can buy it ready-mixed, but mixing it yourself is less costly. Simply put a gallon of straight antifreeze into a large pail, add a gallon of water, and mix. An easy way to mix is to pour it from one pail to another, and back. Tap water in most places contains minerals that will deposit as scale in a cooling system, so you should use distilled water. Don't worry about the cost of distilled water. It's well under a dollar a gallon in most places.

If a radiator isn't doing its job, the first step in trying to remedy that is a thorough cleaning of the cooling system. That includes the radiator, pipe, and engine water passages. Folks use all sorts of things for cleaning out the system. That includes radiator flush from the auto parts store, 50-50 vinegar and water, CLR, Simple Green, Dawn dish soap, and others. Whatever you use, apply it in both radiator and engine passages. I prefer doing them separately. Plug the outlet and fill the radiator with whatever cleaning agent you're using and let it sit for several hours. It helps if the solution is warm, up to about 150º F. After soaking, unplug the outlet and flush the radiator with hot water.

But you may find that cleaning isn't enough to cure overheating. For this you can blame wear and tear and the passage of time. A radiator has tubes which carry the coolant. The tubes pass through thin metal fins. Heat from the coolant spreads to the fins, and the heat from the fins dissipates as it is radiated into the passing air. But on many of these old machines, decades of vibration have caused the fins to separate from the tubes. Without that direct physical contact, heat isn't passed from the tubes to the fins and into the air, and the radiator no longer radiates.

When the radiator no longer does its job, even when clean, you have two choices. One is expensive, and the other is even more expensive. The most costly cure, but often most effective, is simply to buy a new radiator. This is what I did with my black era touring car shown in the flushing video. Even after all the cleaning and flushing, the old aftermarket honeycomb radiator wasn't doing its job. So I bought a new replacement. The cost was about $800. Of course you can buy a used radiator for a lot less, but there's probably a very good reason it's no longer on a car and is for sale cheap.

A less costly measure than buying a new radiator is to have the old one recored. That's what I chose to do with the brass radiator in my 1915 roadster. Cost was one factor, but my main reason for that choice was that the original tank was still good, and I like the original better than the tanks on the new reproduction radiators. A new core allowed me to keep the original appearance, and it saved me a few hundred dollars. The recore in 2016 cost me about $800, and a new brass radiator is over $1200.

For a recore do a Google search for radiator repair shops You may find one near you with the expertise to handle the job. A shop in my area that does recores is:

B & R Radiator, Inc.

1015 West 53rd Street North
Wichita
KS 67204
(316) 838-8497

A source of new Model T radiators is:

Brassworks

The Brassworks
500 Linne Road – Unit I
Paso Robles, CA 93446

Telephone 805-239-2501

Facsimile 805-239-2545

sales@thebrassworks.net

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