03/07/2026 8:38 am
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Automotive Q&A
Audi Q5 EA888 leaves pink residue beneath the intake but passes a cold test
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A 2016 Q5 loses a small amount of coolant over several weeks. Dry pink residue is visible under the intake near the pump and thermostat module, but a 20-minute cold pressure test holds. No coolant reaches the undertray. The odor is strongest after a highway drive.
How can a heat-dependent housing seam be confirmed before replacing the full module?
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04/07/2026 7:13 am
Clean the area, establish a cold level and inspect with a borescope immediately after the exact hot drive, without opening the pressurized system. Leave the tester attached during cool-down if the procedure permits, because some plastic seams open as temperature changes. Approved UV dye can distinguish a fresh track from old residue.
Inspect nearby hose connections and the pump interface as separate sources. Recommend the module only when fresh coolant begins at its seam rather than merely passing across it.
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05/07/2026 10:52 am
A borescope during cool-down showed a new bead forming at the thermostat-module seam while the hose joints remained dry. The repaired module held hot and cold tests, and the reference level stayed fixed for two weeks.