Boxer overheating radiator fan issue

Overheating and a check engine light on a Boxer... When's the last time you checked the coolant level, and have you noticed if the fan is running constantly, or not at all? What's the mileage?

Coolant level is fine. Mileage is 273629 km. The fan IS running, but it's making a real racket and doesn't seem to be doing much cooling. Any chance a defective speed sensor might be involved?

Could be the speed sensor, though it is a long shot. Given the symptoms, especially the noise, it’s quite possibly the radiator fan itself is failing, or a problem with the thermal switch. With that mileage, I'd get it checked out by a professional. A faulty fan can quickly lead to serious engine damage.

Booked it in for a check-up. The radiator fan was indeed kaput, with a defective speed sensor as the likely cause. Cost me about 250€, but at least the overheating is over!