We can’t seem to cool our engine

August 1, 2012 | By Richard Prince


We have a 340 Mopar engine and have installed a serpentine system. We have attempted several changes to the cooling system in an attempt to make the engine operate at 180° F. We added two heater cores in the rear of the car with an electric fan. Our radiator has been checked and the radiator man suggested it was good for a large block.

The radiator expert suggested we restrict the flow, that it was likely the water was flowing too fast through the radiator. We installed a restricting washer on the upper radiator spout (5/8” hole) on the radiator return. We have a pull fan on the inside of the fan. The pull fan is about 3/4 the size of the radiator. The top and bottom is open around the fan. We have an A/C Condenser on the front of the radiator. These changes have accomplished little to solve the cooling problem. Idling we will slowly run up to 200-degrees. The present rotation of the engine produces a counter-rotation of the water pump. Could this be the problem? Question, do we need a bigger, high-volume aluminum radiator? Would a push fan in front of the radiator make a 30-40% difference?

Thank you for some ideas.


I’m not entirely sure what you mean when you say that the “present rotation of the engine produces a counter rotation of the water pump.” There is only one correct and acceptable direction your water pump should be turning. Make sure it’s turning in the correct direction for the model year engine that you have.

You mention that there’s an A/C Condenser in front of the radiator. This may contribute to a hot running condition by obstructing the flow of air through the radiator. If the car has a functional A/C system the position of the condenser aggravates a hot-running situation by pre-heating the air that flows through the radiator. A large fan on the engine side of the radiator should pull air through the radiator and help cool the engine, but you mention that the top and bottom around the fan are open. This doesn’t help matters because air will normally seek the path of least resistance and if the air the fan is displacing can be drawn from around it, where there are no obstructions, or from the other side of the radiator, where it has the task of passing through the radiator, far more of it will be drawn from around the fan rather than from in front of the radiator. A fan shroud around the fan, with foam seals along the edges to help seal the shroud to the radiator, will be quite helpful.

If your water pump is spinning in the correct direction and pumping engine coolant and if your radiator is in good working order and the engine is still running hot, even without auxiliary fans, there is some underlying problem you should try to solve.

Have you gone through all the basics, such as ignition timing, internal exhaust gas leaks, air pockets in the coolant, air/fuel mixture, etc? Has the cylinder block been excessively over-bored?