Radiator Overheating Solutions

Question:  I have a new radiator and a pusher 16” fan in front of my radiator, but my car is still overheating.  What can I do to remedy this problem?

Answer:  A pusher fan is the least efficient means of cooling a radiator.  You should really use a full shroud on the rear of your radiator with a puller fan.  A pusher fan is only pushing air around the diameter of the 16” fan, which results in the loss of cooling effects in all other uncovered parts of the radiator. 

By using a full shroud on the rear of the radiator and a puller fan attached to the shroud, you are pulling air through the entire area of the radiator fins.  Another thing to watch for in buying fans, some fan manufacturers have an “FCFM rating” and claim up to 3,000 FCMF.  FCFM stands for “Forced Cubic Feet per Minute” which is a measurement taken when the vehicle is moving down the road with air being forced through the fan.    What you should be looking for is just “CFM” in the manufacturer’s advertisements.  “CFM” stands for “Cubic Feet per Minute” which is measured when the car is standing still and no air is being forced through it. 

Suggestion:  You should also be using an expansion tank –the bigger the better.  When you fill your radiator up when the engine is cool, the expansion tank should be empty because as water gets hot, it will expand pushing the water into the tank.  As the car cools down, the radiator creates a vacuum which sucks the water from the expansion tank back into the radiator. 

Suggestion:  You should be running a 16 lb cap for every pound of pressure you apply with your radiator cap, you will gain 3 degrees of boiling point to the water and antifreeze.  By doing the math, 3 X 16 = 48, thus turning 212 degree boiling point at sea level into 260 degrees boiling point at sea level. 

Suggestion:  You do not state whether you have an automatic trans cooler built into the radiator.  If you do have, this can add temperature to the coolant during the summer months.  Most street rods are not utilized during the winter months.  Therefore, they should have external trans coolers.  But if you are using this vehicle during the winter months, you should really use an internal trans cooler to pre-heat the transmission fluid. 

Wiring an Electric Fan

Question:  I want to use an electric fan for my radiator, but do not know the proper way to wire it. Do I wire it directly to the key switch so any time the motor is running, the fan is running?

Answer:  No, never wire a fan directly to a key switch.  The proper way to wire your fan is to use a relay kit and a temperature sender.  The temperature sender should go into the  intake manifold because the intake manifold point is approximately 8 degrees hotter than the head location.  The fixed temperature senders range anywhere from 180-200 degrees turn on temperature and will turn off again at ten degrees less than the turn on temperature.  This temperature sender will be wired into the control circuit of the relay so when the temperature sender turns on the ground of the control circuit for the relay, it will pull in the relay for the main line to your fan. 

Also, if you are using air conditioning in your vehicle, you should provide a trinary switch.  A trinary switch will also turn the electric fan on at 280 psi in the high side of your air conditioner.  By doing this you will not notice any difference in the temperature of the air coming out of your air conditioner.  The reason you should use this switch and temperature sender is due to the fact that when you are traveling at highway speeds, there is enough air coming through the radiator and condenser to cool the car without a fan.  This saves the life of your electric fan and your alternator.  But then when you come into traffic at lower speeds, the motor will heat up and the fan will automatically come on by itself.  Please refer to the wiring drawings below: