Lawsuit Says Subaru Thermo Control Valve Defect Can Cause Engine Overheating, Failure

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A proposed class action alleges certain model year Subarus suffer from a defect that can cause a vehicle’s thermo control valve to fail, increasing the risk of engine overheating or premature failure during operation.

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The 85-page Subaru lawsuit says the thermo control valve defect affects 2019-2021 Crosstrek, Forester, Legacy and Outback models (the class vehicles) and can manifest without warning, rendering the vehicles “unsuitable for their intended purpose.” The case alleges the automaker has known of the problem since at least 2021, when it updated the design of the thermo control valves in the wake of numerous failures and a bevy of consumer complaints. 

Despite its apparent knowledge of the problem, Subaru has failed to fix the thermo control valve issue, with the automaker’s purported remedy, a design update, proving ineffective, the filing says. 

“As a result, Plaintiffs and Class Members have been forced to pay out of pocket for replacements to their thermo control valve,” the complaint states, accusing Subaru of “[engaging] in a pattern and practice of avoiding its warranty obligations with respect to the Defect.”

According to the suit, the thermo control valve (also known as the temperature control valve or thermostatic control valve) is critical for maintaining optimal engine temperature and preventing overheating. The component, meant to replace traditional vehicle thermostat designs, works by detecting the temperature of a vehicle’s engine coolant and, based on that temperature, allowing a certain amount of coolant to flow through to the engine to cool it down, the case explains. 

The thermo control valve, located under the intake manifold, is faster than a traditional thermostat at responding to engine temperature changes and can thus help achieve better fuel economy, according to the suit. 

The problem, the lawsuit says, is that the Subaru thermo control valves at issue are manufactured from plastic instead of a stronger material that can withstand continuous cycling of high temperatures and regular vehicle vibrations. Per the suit, the thermo control valves “see repeated heat cycling of engine coolant temperatures to approximately 220 degrees Fahrenheit.” 

Overall, the plastic and “sub-par materials” used by Subaru to manufacture the thermo control valves are “entirely inadequate and prone to premature failure and cracking,” the suit claims. Ultimately, when a valve fails, it is unable to sense the temperature of an engine and thus fails to allow a proper amount of coolant to circulate throughout, the case says. 

When the problem manifests, a driver will typically see their check engine light illuminate, and certain safety features, including Brake Assist, Eyesight Driver Assist, Lane Keep Assist and others, will be disabled, the complaint adds. The suit shares that even just a few minutes of engine operation at excessively high temperatures can cause catastrophic damage. 

“When the Defect manifests and the thermo control valve fails, engine coolant cannot flow through the engine as intended, the engine in the Class Vehicle overheats, and the vehicle becomes inoperable,” the filing summarizes. “Because the engine cannot maintain a safe operating temperature, continued operation of the Class Vehicle can cause catastrophic engine damage. As a result, drivers become stranded and must seek roadside assistance or alternative means of transportation.” 

The case goes on to argue that Subaru’s new vehicle limited warranty and five-year powertrain limited warranty cover the thermo control valve problem, yet when drivers take their cars in for service, the automaker allegedly refuses to fix the issue and tells drivers that the necessary repairs and replacements are not covered. 

The lawsuit looks to cover all persons in the United States who bought or leased any of the Subaru vehicle models highlighted on this page. 

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