u/6inarowmakesitgo

If you have an automatic transmission N52 E9x vehicle and have a persistent 2EF4 code *you must verify radiator does not have an internal leak!*

The lower hose connection on the outlet tank of radiator is an *inlet* from the water pump outlet to block pipe. Flow control through here is dependent upon transmission cooler thermostat. What happens is the internal gasket allows coolant to bypass the thermostat and causes slow warmup times and bad cabin heat with low ambient temperatures. Also verify the cooler thermostat blocks flow when cold. Some aftermarket units have only one control sleeve on the inlet tank of radiator, these *will* cause bypass issues.