Subaru Legacy overheating issue caused by air trapped in heater element requiring bypass solution on Subaru Legacy

Submitted by AnthonyvT · Jun 23, 2025
Published by RepairPal

Problem overview

Some Subaru Legacy owners report experiencing overheating issues caused by air trapped in the heater core. This problem can lead to significant engine temperature increases if not addressed. One potential solution that some owners have implemented is disconnecting the heater hoses at the heater core and connecting them together with a fitting to bypass the heater core entirely. By using this bypass method, owners have found it effective in alleviating the overheating problem related to trapped air in the system.

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Subaru Legacy vehicles with this problem

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