What's in a Color When it Comes to Radiator Fluid?
The coolant color game continues to confuse many in the auto radiator repair industry. Hopefully this easy reference will help!
 
 Yellow Coolant: Valvoline G-05, CelCool, Ford Truck factory fill
 Red-Orange or "Strawberry" Red: Detroit Diesel PowerCool Plus, Texaco & CAT ELC, and International & GMC Truck factory fill.
 Fuchsia: FleetCharge, DDC PowerCool, CAT DEAC, factory fill at Mack and Freightliner.
 Green: Many fully-formulated brands including Prestone HD, factory fill at KW & PB, unfortunately easily confused with conventional automotive.
 Blue: Cummins-Fleetguard Compleat.

Consequences of Your Car Radiator Overheating
If the engine overheats, the first thing that will happen is a gasoline engine will start to detonate. The engine will ping and start to lose power under load as the combination of heat and pressure exceed the octane rating of the fuel. If the detonation problem persists, the hammer-like blows may damage the rings, pistons or rod bearings. Overheating can also cause preignition. Hot spots develop inside the combustion chamber that become a source of ignition for the fuel. The erratic combustion can cause detonation as well as engine run-on in older vehicles with carburetors. Hot spots can also be very damaging and burn holes right through the top of pistons. Another consequence of overheating may be a blown head gasket. Heat makes aluminum swell almost three times faster than cast iron.  The resulting stress can distort the head and make it swell in areas that are hottest, like those between exhaust valves in adjoining cylinders, and areas that have restricted coolant flow like the narrow area that separates the cylinders. The typical aluminum head swells most in the middle, which can crush the head gasket if the head gets hot enough. This will cause a loss of torque in the gasket allowing coolant and combustion leaks to occur when the head cools.

How Hot Is Too Hot?
Most engines today are designed to operate within a "normal" temperature range of about 195 to 220 degrees F. A relatively constant operating temperature is absolutely essential for proper emissions control, good fuel economy and performance.

A 50/50 mixture of water and ethylene glycol antifreeze in the cooling system will boil at 225 degrees if the cap is open. But as long as the system is sealed and holds pressure, a radiator cap rated at 15 psi will increase the boiling temperature of a 50/50 coolant blend up to 265 degrees. If the concentration of antifreeze to water is upped to 70/30 (the maximum recommended), the boiling temperature under 15 psi of pressure goes up to 276 degrees.

So does this mean a cooling system with a maximum concentration of antifreeze in the coolant (70 percent) can run as hot as 276 degrees without boiling over? Theoretically yes - but realistically no. The clearances in most of today's engines are much, much closer than those in engines built in the 1970s and early 1980s. Piston-to-cylinder clearances are much tighter to reduce blowby for lower emissions. Valve stem-to-guide clearances also are closer to reduce oil consumption and emissions, too. Plus, many engines today have aluminum heads with overhead cams. Such engines don't handle higher than normal temperatures well, and are very vulnerable to heat damage if the engine gets too hot.

Anytime temperatures climb beyond the normal range, the engine is running in the danger zone.