An excerpt from BMW's Service Information No. SI 11 001 16:
"The coolant pump is fitted with a radial shaft seal on the oil-side and on the coolant-side is a mechanical seal. Mechanical seals are reliable and durable, yet for technical reasons, they always exhibit minor seepage. The seepage amount is considered to be within permissible limits if the coolant does not need to be topped up between service intervals.
The drain hole (arrow in the figure) of the coolant pump is in plain view. Even small, inevitable seepage is noticed and often perceived to be a faulty coolant pump. In many such cases, fault-free coolant pumps are replaced.
In order to reduce misdiagnosis and repeat repairs, a drain hose is retrofitted. The hose diverts the seepage away from the field of view to under the engine. Yet large amounts of leakage that indicate a faulty coolant pump will be noticed.
Vehicles affected
All K7x models above without a drain hose from the coolant pump.
Production Solution
As of August 2014 onwards (model year 2015), the drain hose has been installed in production.
Service solution
The drain hose is to be retrofitted as described in work items 11 51 030 and 11 51 530 on the current RSD (Repair and Service."
