Without getting mired too deep in chemistry, the basic terms for the qualities of a coolant are: molecular weight or solubility, hygroscopicity, vapor pressure and boiling point, viscosity, freeze point, specific heat, density, surface tension, air contact, flammability, refractive index and toxicity.
Traditional antifreeze is a 50/50 mix of ethylene glycol and water that is often abbreviated as EG.
Heat is transferred from the cylinder bore and cylinder-head walls to the liquid coolant via convection or semiconvection phases. These phases are dependent on the rate of heat flow through the metal-per-unit area along with the temperature difference between the metal surface and the liquid coolant. As the coolant reaches the hottest part of the cylinder head, which is usually around the combustion chamber and exhaust valve, it will actually start to boil. This phase change is identified as the nucleate boiling point and allows efficient transfer of heat. The coolant's chemical and thermal reaction are responsible for how efficient this process becomes.
When the coolant first comes in contact with the hot metal, it will boil, changing phase, and then due to the pressure in the cooling system, the gas bubbles will be pushed from the localized boiling spot and carry with it the heat. It then recondenses into a liquid.
The coolant can experience four distinct phase changes:
• Convection Phase
At very low rates of heat flow into the coolant, no boiling occurs, and the movement of the liquid is by free convection or by forced convection, caused by the water pump pressure. In a cooling system, the majority of the heat transferred from the cylinder bores to the coolant occurs by natural and forced convection currents where the heat flow through the metal is relatively low.
• Nucleate Boiling Phase
At higher engine loads and speeds, the rate of heat flow through the cylinder head is increased until steam bubbles are formed in certain regions on the surface of the water jacket. These areas are the metal bridge between the exhaust valve seats, spark-plug boss, and so on. Nucleate boiling involves the nucleation and growth of vapor bubbles that originate at sites of high temperature. In this phase, large numbers of bubbles form on the hot surfaces and travel through the bulk of the coolant, later recondensing as they move to a lower temperature region.
• Unstable Film Boiling Phase
Under severe engine load and speed, the vapor bubbles become so large and numerous that the liquid has difficulty flowing back to the hot metal surface of the cylinder head. When this critical heat flux is reached, the hot surface of the water jacket suddenly becomes insulated by individual steam bubbles, which join together to form a film. Under these conditions, the film insulates the water jacket from the coolant and metal surface temperature of the cylinder head elevates dramatically and can cause the engine to ping even though the temperature gauge shows no sign of this condition. This phase is often called crisis boiling.
• Stable Film Boiling Phase
If the metal surfaces subjected to unstable film boiling can withstand even higher heat levels without melting, the temperature is raised further by increasing the difference between the metal surface and the liquid boiling temperature, until a stable film is formed. With stable film boiling, heat transfer is now mainly by conduction and radiation across the vapor film. At this time, engine failure is very possible.
In every Pontiac engine the first two phases of coolant boiling occurs (in the cylinder head), while the last two will be experienced when either the horsepower level is too high for the coolant or the system is not designed properly.
Whenever a drivebelt is removed...
Whenever a drivebelt is removed (v-design or serpentine), it's important to note the direction of rotation so that it's installed the same way. Over time, the molecular structure will take a set from being pulled one way and if installed backwards, will stretch excessively and possibly fail or fall off. This wasn't a problem with this project as a new, 1-inch shorter belt (shown) would be used. The original belt was Dayton PN 5060960.
With the drivebelt out of...
With the drivebelt out of the way, the stock water pump came off without issue.
Evans wants a 1/8-inch hole...
Evans wants a 1/8-inch hole to be drilled in the sheetmetal plate (seperator) behind the water pump. This allows the bleed on the pump to function and eliminate any air pocket and thus, cavitation. The hole connects the suction and pressure sides of the pump.
With the template cut out...
With the template cut out and placed on the separator, Rich center punched a mark through the paper and onto the plate. He then drilled the 1/8-inch hole.
With the Prep Fluid drained...
With the Prep Fluid drained and saved for another installation, the NPG+ becomes a straight pour in. On a fresh engine build, none of this would need to be done. The only time the Prep fluid is used is if the engine is already in service with water-based coolant.
With the new water pump and...
With the new water pump and thermostat installed, the next step was to add 2 gallons of Prep Fluid to the engine and run it for a few minutes. This fluid is used to pull any remaining water from the system.