Common Causes for Overheating in a Model T

The most common cause of overheating for a Model T that has an original or vintage radiator is a bad radiator. As the old radiators age, the thin fins that are fastened around the tubes become loose from the tubes. This is caused by the fact that through the years, the assembly has expanded and contracted thousands of times from heating and cooling. If the fins are loose, they do not dissipate the heat to the air flowing through the radiator and, therefore, do not provide the cooling effect they were designed to do. There is nothing that can be done except to replace a bad radiator.

A vintage radiator is also commonly clogged with crud from the engine that either blocks the flow of water or insulates the hot water from the metal in the radiator, thereby reducing its cooling efficiency. One of the easiest ways to clean a radiator is to put dish washing detergent, such as Cascade, into the radiator and run the engine for about 20 minutes or until it heats up thoroughly. Use the same amount of detergent as you would for washing a load of dishes. After the coolant has heated up fully, drain it and put fresh water in the radiator and run the engine again for about 20 minutes. If the fresh water is reasonably clean when you drain it, fill the radiator with coolant and hope you have fixed the problem.

First, make certain you have the proper amount of water and coolant in the radiator. A 50-50 solution of water and coolant works best for the Central Texas region. Make sure you do not have the water/coolant level too high because when the coolant heats, it will expand and come out the radiator cap. That can give one the false impression that the car is overheating.

Second, remember that under certain driving conditions, such as driving through mud, thick sand, up long hills, in stop and go city traffic and slow moving parades, overheating is to be expected, especially in hot weather. Your Model T engine was designed to operate at its greatest efficiency when the water is heated to almost the boiling point.

Third, your driving style could be the cause of the overheating problem. Make certain you avoid driving too much in low speed, and be sure you are not retarding the spark too far. Also, do not race the motor.

Finally, the overheating problem could be caused by a mechanical problem such as carbonized cylinders, poor ignition, a lack of oil, use of a poor grade of oil, a clogged muffler, improper adjustment of the carburetor, improper angle of the fan blades, a broken fan or fan belt, clogged radiator tubes or a slipping fan belt.

The bottom line is not to panic if your Model T boils over occasionally. But if the problem is persistent under normal driving conditions, be sure to get it fixed.

Model Ters often ask if it is okay to fill the radiator with cold water if they are on the road and the radiator overheats? According to the Ford Manual, circa 1921, if the radiator is hot and totally empty of water/coolant, DO NOT add water/coolant until the motor is allowed to cool. If the radiator is not totally empty, then it is okay to add more water/coolant without having to wait for the engine to cool.

Contributed by Ernie Wentrcek and Ben Hardeman ~ February 2008

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