Rick's Free Auto Repair Advice

What causes Dex-Cool sludge

Dex-Cool sludge – Cause or effect?

Dex-Cool® coolant is a registered trademark for a coolant used in GM vehicles. Dex-Cool is an orange coolant is based on an organic acid technology that provides longer life than traditional silicate based formulas. It has been blamed for causing gasket failure and sludge buildup in cooling systems. There have been class action lawsuits claiming that Dex-Cool causes gasket failure and sludge.

Does Dex-Cool cause sludge?

Dex-Cool sludge is caused by neglect and not following directions. If a shop or owner fails to maintain the system, adds an incompatible coolant to top it off, or runs the vehicle too long without changing the coolant or runs the cooling system when low.

Dex-Cool compatible coolants

Even though several coolant manufacturers state that their coolant are compatible with Dex-Cool. The ONLY coolants that can be added to Dex-Cool are those that have been licensed by GM. GM approved brands include Dex-Cool coolants made by Chevron, Shell, Prestone, Valvoline, ACDelco and GM Vehicle Care. NO OTHER COOLANTS can be mixed with Dex-Cool. You may think that this alone means Dex-Cool is a bad coolant to use. But with the many different types of materials in modern engines, virtually ALL automakers not specify a certain type of coolant and further state that no substitutions can be used or any other type of coolant added to top off the vehicle.

Dex-Cool sludge is caused by oxidation

A faulty radiator cap, coolant additives and stop leak products, mixing a different coolant into Dex-Cool, running low on coolant or using Dex-Cool in an engine not approved for its use can all cause oxidation and corrosion that forms as a sludge. To avoid sludge, you must keep the system full so air doesn’t enter. The radiator cap must work properly.

Does Dex-Cool clog heater cores?

NO. Early heater core failure is caused by failing to change coolant leaking heater coreat the recommended intervals, mixing other coolants into Dex-Cool, removing a heater core flow restrictor. Erosion or too high a flow and electrolysis are the two most common causes of heater core failures. Electrolysis occurs when the anti-corrosive additives in Dex-Cool are depleted OR, if the a ground strap has been left off or has a poor connection. ALL vehicle brands can suffer heater core failure if routine maintenance schedules aren’t followed.

heater core flow restrictor

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Posted on by Rick Muscoplat

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