I need help with my overheating

June 1, 2010 | By Richard Prince


I live in Glendale, California, and own a 1950 Ford Business Coupe with only 23,246 miles. I have owned my coupe for eight years. It is mostly un-restored, with one repaint in 1971, but the original Flathead eight, three-speed on the column with overdrive, interior and trunk are untouched and totally original.

I have an overheating problem that I have not been able to solve because my mechanical ability is limited. If you could recommend a mechanic, restoration shop or whomever you think can solve my overheating problem in the Los Angeles, Orange, Ventura or San Diego county areas I would really appreciate it.

I have done the following to try to solve the overheating problem: Installed the largest stock radiator available (but used the same four-blade fan), had H & H Flatheads in La Crescenta, California, clean all the debris out of the bottom of the block and install new thermostats and hoses, and tried different mixtures of antifreeze and water.

I know there are many other things that can cause the overheating (water pumps, obstruction in the block, etc.) and I need a professional to figure out the problem.


Overheating is a relatively common problem with Flathead Ford and Mercury engines. An inherent problem with virtually all L-head engine designs, including Flathead Fords, is that the exhaust gases have to travel a relatively long distance through the engine before exiting into the exhaust manifolds. This allows a high percentage of the heat in the exhaust gases to be transferred to the engine’s components and coolant. Ford’s engine designers were well aware of this issue and configured the radiators and other cooling system components in their cars accordingly.

So, if everything in your 1950 coupe that’s related to engine temperature control is working properly then it should not overheat. The fact that it is overheating tells you something is wrong.

Thin cylinder walls will often cause an overheating condition. Though unlikely in your case, it is still possible that the engine’s cylinders have been excessively enlarged. You mention that you’ve installed the “largest stock radiator available” but you don’t say whether you used a brand-new radiator or a used one. A new radiator is always preferable to a used or reconditioned one.

Make sure ignition timing is correct because late timing will cause the engine to run hotter. In addition to initial timing, check total advance to ensure that it is correct. A very lean fuel mixture will raise engine operating temperature. An incorrect head gasket can block coolant flow but you won’t know if this is the problem without removing the heads. A warped or cracked head or defective head gasket can allow exhaust gas to enter the coolant. This can be easily diagnosed with a test kit designed for that purpose.

A defective water pump may be the source of the problem. The pump’s impeller may be spinning on the shaft or faulty seals may be allowing air to enter the coolant. Air bubbles in the coolant reduces its ability to transfer heat.

If all else fails, you may want to consider changing or modifying the water pump. Beginning in 1949, Ford redesigned the Flathead water pump to flow approximately 75 gallons per minute at 4000 engine rpm, which is about 25% more coolant flow than the earlier pumps had. The redesigned pumps had eight vanes in place of the earlier-design pump’s six vanes. The new vanes also had a more efficient shape that enabled them to move more coolant. Some respected Flathead specialists believe that the second-design pumps enhance cooling capacity by virtue of the added coolant flow rate. The additional coolant pressure that results is also thought to reduce the likelihood of vapor bubbles, which lead to hot spots and the propensity to overheat. However, other Flathead enthusiasts believe that the second-design pumps actually did more harm than good because they moved the coolant through the radiator too fast for efficient removal of the heat. Subscribers to this theory maintain that engine temperature will be reduced if the older, slower pumps are installed in place of the newer, faster ones, or if the newer pumps are modified with the removal of every other impeller fin so that they flow less coolant. The later pumps can normally be used on earlier engines but the modified impellers have to be trimmed to eliminate an interference problem.

I don’t happen to know of a Flathead specialist in the Glendale, California, area but I am sure there are at least a couple within a reasonable distance from you. Maybe readers who know of someone good near you will let us know.

You can probably also get to a good mechanic through the recommendations of other vintage car enthusiasts in your area. You can find other old car fans through local clubs and cruise spots.