MK7 GTI pink residue below the intake: water pump or an old spill?

Question

A 2016 GTI has dry pink residue below the intake near the pump and thermostat module. Coolant is at the lower edge of the normal range, but the owner does not know whether it has changed recently. The upper hoses and expansion tank are clean, and there is no wet spot after parking.

Because old coolant can leave a convincing trail, what checks would separate an active pump or thermostat-module leak from residue left by previous service? I would like to establish a baseline before recommending a fairly involved repair.

CoolantTrail · Accepted Answer

Photograph the current level cold, clean the residue completely and inspect the module with a mirror or borescope before and after a pressure test. Watch the housing seam, pump interface and nearby hose connections; do not assume every pink track started at the pump. A sheet of clean paper below the area can also reveal a fresh drop that the undertray would hide.

If it holds cold, inspect immediately after a full warm-up and again during cool-down. A UV dye approved for that coolant can help when evaporation is fast. The recommendation should be based on a new wet track or measurable level change after the baseline, not the color of an old deposit alone.