A failing turbo gives warnings weeks before it lets go. Spot them and you're looking at a £400 actuator. Ignore them and you're looking at £2,500+ for a new turbo and possibly an engine.
Symptom 1 — blue smoke under load
Oil getting past the turbo shaft seals. The turbo's days are numbered.
Symptom 2 — whining / siren noise
Turbo bearing wear. Most audible when boost builds.
Symptom 3 — turbo lag worse than before
VNT vanes sticking with soot, or actuator failing. Often clean-able if caught early.
Symptom 4 — limp mode under acceleration
Overboost or underboost fault codes. Pressure not matching the ECU's expected curve.
Symptom 5 — oil consumption
Failed seals dumping oil into the intake. Check oil level weekly if suspected.
Mobile turbo work
Actuator replacement, vane cleaning and full turbo replacement all possible mobile on most platforms.