Concept: Mechanical fans cool better than electric.
Theory: Our worst overheating occurred on throttled drives up sand dunes. The mechanical fan should increase airflow through the radiator as engine speed increases.
What we did: We removed the 14-inch electric fan and fitted a 14-inch Flex-a-lite flex fan to the engine. These fans are designed to deliver maximum airflow at lower engine speeds, and the blades flatten slightly at higher speeds to minimize horsepower loss.
Every cooling problem is caused...
Every cooling problem is caused be inadequate airflow, water flow, or heat-transfer capability. We attempted to improve airflow at higher engine speed by replacing the electric fan with a Flex-a-lite metal flex fan and then a Flex-a-lite plastic fan.
Cost: $30 for the stainless steel model we used.
What happened: The electric fan moves more air at slow engine speeds, so overheating at idle was a bigger problem with the mechanical fan. Cooling at higher engine speeds was not improved.
Concept: Same as above, but with a plastic flex fan.
Theory: We've used Flex-a-lite's 400 Series plastic fans before with great success. They're popular with off-roaders because a sheet of metal screen over the radiator will cause the fan to break instead of destroying the radiator if contact occurs.
What happened: The engine ran slightly hotter on the sand dunes, verifying that this fan cannot move as much air as the metal flex fan at higher engine speed.
Concept: Every mechanical fan should have a shroud.
A fan shroud directs the airflow...
A fan shroud directs the airflow of a mechanical fan through the radiator instead of around it. We tested with and without a fan shroud to prove or disprove this theory--we may have only confirmed that we have bigger problems.
Theory: Without a fan shroud, the fan will draw air from the source of least resistance--around the radiator instead of through it. The blades of the fan need to be half in and half out of the shroud to avoid just circulating the air inside the shroud.
What we did: Because everything is custom under the hood of the Jeep, we had to make our own shroud. At a local hardware store we picked up metal supplies and rubber insulation to create a shroud and seal it safely to the radiator.
What happened: This had virtually no improvement compared to the previous test. This was our first confirmation that we aren't able to move air through the engine compartment.
Concept: An inefficient water pump could be causing excessive cavitation.
Theory: Cavitation is the production of small vacuum pockets that disrupt fluid flow. These pockets of air greatly decrease the efficiency of the pump. It isn't able to move as much water through the cooling system.
What we did: Replaced the aftermarket aluminum water pump with a new GNB water pump from AutoZone.
Evans Cooling NPG+ is a radical...
Evans Cooling NPG+ is a radical idea in coolants. It concentrates on improving heat transfer in addition to raising the boiling point and lowering the freezing point. To ensure the system is free of water, you can hot purge the system by running the engine at about 275 degrees which will vaporize the water, pushing it out the overflow hose. We experienced no engine damage during this process.
What happened: There was no difference in any of our testing, indicating that excessive cavitation at the water pump was not a problem.
Concept: A lean air/fuel mixture will cause an engine to run hot.
Theory: An excessively lean air/fuel mixture causes an engine to run hot because of its high air content. Adding fuel to the mixture (making the mixture richer) should lower the operating temperature.
What we did: Our 385hp engine requires a fuel curve radically different than a stock engine. It needs more air and fuel at idle and in the part-throttle circuit as well as the deep-throttle circuit. This requires modifications beyond jets and metering rods, so we had JET Performance build a Stage 2 Q-Jet custom for our application.
What happened: We had lots more power on the sand dunes--and we do mean lots. Lots more power means lots more heat. However, the engine ran cooler at all points except idle, where it ran the same temperature as before.
Win this. Plus a 4-Wheel plate...
Win this. Plus a 4-Wheel plate and sticker.
Concept: Water has better heat-transfer properties than antifreeze.
Theory: Because 100-percent water can transfer heat (the name of the game in engine cooling) better than antifreeze or a mixture of antifreeze and water, running all water in the cooling system should lower operating temps.
What we did: Drained all antifreeze from the radiator and the engine (small-block Chevys have a water-jacket drain plug on each side of the engine) and replaced it with 100 percent water.
What happened: It ran cooler. There are two major drawbacks: 100 percent water promotes corrosion in iron and aluminum engine parts and will slowly destroy your engine and aluminum radiator. And water freezes, which will cause engine damage this winter, making the first drawback not as important.
Concept: Coolant isn't staying in the radiator long enough to cool before returning to the engine. Theory: Adding a restriction to the coolant flow path should keep coolant in the radiator longer, cooling it more. A thermostat will create this restriction. If the operating temperature lowers enough, the thermostat will close, holding the coolant in the radiator even longer, cooling it even more.
What we did: Installed a 180-degree thermostat from AutoZone.
What happened: Operating temperatures increased at all test points. This told us that restricting flow was not beneficial and led us to believe that greater flow may be beneficial. The thermostat was removed for the remainder of the testing.
Concept: There are coolants better than typical antifreeze.
Theory: Antifreeze will keep your engine coolant from freezing in the winter, and it raises the boiling point of water. It doesn't really do anything to improve heat transfer (remember, that's the idea of a cooling system). Evans Cooling offers NPG and NPG+ non-aqueous propylene glycol products. We used NPG+ which has a freezing point of -40 degrees (compared to -30 degrees for 50/50 water/ethylene glycol antifreeze mixture) and a boiling point of 375 degrees (255 for a 50/50 mix of water/antifreeze).
This higher boiling point means that there is liquid coolant around hot spots in the engine such as the exhaust valve areas in the heads. Water and 50/50 mixes of ethylene glycol-based coolants vaporize in these areas and lose their ability to transfer heat. The operating temperature will probably not decrease (in fact, it may increase slightly). The fact that there will be heat transferred from the hottest spots in the engine means the engine will escape damage up to 280 degrees. This coolant also has anticorrosion properties, and its lifetime is indefinite--you'll never need to change it.
What we did: Completely drained the coolant and replaced it with Evans Cooling NPG+.
Cost: $22 per gallon, $66 for our application.
What happened: The operating temperature didn't decrease, but the engine did run at a higher temperature without spitting coolant into the overflow. This seemed to confirm what Evans Cooling claims about its product. Our testing procedure included two idling tests and a casual drive at part throttle, but the sand dunes proved to be the toughest part. Horsepower is heat, and several blasts over and around the dunes built plenty for the cooling system to try to deal with. Every cooling problem is caused be inadequate airflow, water flow, or heat-transfer capability. We attempted to improve airflow at higher engine speed by replacing the electric fan with a Flex-a-lite metal flex fan and then a Flex-a-lite plastic fan. A fan shroud directs the airflow of a mechanical fan through the radiator instead of around it. We tested with and without a fan shroud to prove or disprove this theory--we may have only confirmed that we have bigger problems. Evans Cooling NPG+ is a radical idea in coolants. It concentrates on improving heat transfer in addition to raising the boiling point and lowering the freezing point. To ensure the system is free of water, you can hot purge the system by running the engine at about 275 degrees which will vaporize the water, pushing it out the overflow hose. We experienced no engine damage during this process.