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Proper Car Cooling System Maintenance

Choosing the Right Formula and Ratio is Critical to Avoid Parts Failures

It is extremely important to flush and refill the cooling system with the OE recommended coolant, whether you are just performing cooling system maintenance or when changing a water pump. This will ultimately help avoid any type of premature part failure.

Coolant has changed dramatically in the last 20 years. All modern vehicles started using organic acid coolants (OAT) in 1996 with GM DexCool. Most all other automakers adopted OAT coolants after that. Asian carmakers use a version called PHOAT, which is a phosphate hybrid OAT. However, silicate coolant still accounts for nearly 60% of all antifreeze sales when estimates suggest the numbers should be closer to 20%. That means there’s likely a lot of maintenance jobs being carried out with the wrong coolant.

The Role of Inhibitors in Antifreeze/Coolant

The inhibitors are most important in the coolant formulation because they help protect the cooling system and other components from cavitation erosion, corrosion, rust, scale and foaming. It is not only the quality of the inhibitors used, it is also the amount and blending of each inhibitor that provides the cooling system with the ultimate protection. Inhibitors make up 1.5% to 4% of the concentrate depending on if they are inorganic compounds, organic compounds or a combination of both.

All inhibitors have a certain level of protection in time or mileage rated by the OE for factory fill coolants. The duration of protection can be affected by outside influences, such as water quality, overheating, contamination or over concentration of inhibitors.

When using an inorganic acid technology coolant in today’s vehicles, and not changing the coolant on a proper maintenance schedule, the inhibitors may deplete or dropout after years of use. This can result in corrosion, rust and other solids, in the cooling system. These solids can be abrasive to water pump seal designs and may lead to premature water pump replacement. Solids in the cooling system can also cause deposits on hot heat exchangers, leading to poor heat transfer, localized overheating and unnecessary repairs.

Antifreeze/Coolant to Water Ratio

When used in a vehicle, the coolant concentrate is mixed with water between a ratio of 40% to 60% for best freeze point protection, boil‐over control and heat transfer. For a fully concentrated or a 50/50 pre‐mixed coolant, the inhibitors are a key effectiveness differentiator for corrosion protection.

In the U.S., most original equipment manufacturers factory fill vehicles at a 50:50 ratio of water to coolant. Typically, they recommend not going beyond a ratio of 40:60. In climates with extremely cold temperatures the ratio may be a 30:70 ratio of water to coolant. However, if you’re not careful and the ratio includes less than 30% coolant, the vehicle may end up with raised freeze points and lower boiling points. Other problems that can occur include metal corrosion, potential water pump cavitation pitting and localized overheating.

Problems that may arise with more than 70% coolant are poor heat transfer, raised freeze points and higher metal temperatures that may also lead to localized overheating. In addition,  the vehicle may run into additive precipitation; this is known as inhibitor drop out and may lead to slushing of the coolant as well as water pump leakage.

Whatever you do, be sure when you are conducting a flush and fill or a water pump replacement, always use the OE-specified coolant chemistry. The seal in the pump is designed to only work with this chemistry.