The N54 engine sees failure at the plastic cylinder head outlet adapter connecting the cylinder head to the thermostat hose. For N54 3.0L twin-turbo motors 335i, 335xi, 135i and 1M. For BMW 1 Series E81/E82/E87/E88 125i 128i 130i 135i 135is 1M 2008-2013.
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