Why turbochargers fail: oil, dirt, heat

A turbocharger is a precision component: its shaft spins at enormous speed and rides on a thin film of oil. That's why most failures are caused not by the turbo itself but by the conditions it works in.

1. Oil

This is cause number one.

• Oil starvation. If oil arrives late or in too small a quantity — a blocked oil feed, low oil level, a failing oil pump — the turbo bearings wear out in minutes.
• Dirty or old oil. Abrasive particles in the oil act like sandpaper.
• Blocked oil drain and high crankcase pressure. Oil can't drain from the turbo and is pushed out past the seals — hence smoke and oil consumption.

2. Dirt and foreign objects

• Dust getting past a damaged or poor-quality air filter gradually erodes the compressor wheel blades.
• Any object in the intake or exhaust — a bolt, a washer, a piece of a valve — instantly damages the wheel.
• Oil and debris left in the intercooler from the old turbo kill the new one.

3. Overheating

• Switching off the engine straight after hard driving — the oil in the hot turbo cokes up.
• Engine and fuel system faults raise exhaust gas temperature.
• Carbon in the variable geometry mechanism makes it stick and causes boost errors.

How to protect your turbo

Change the oil and filters on time, look after the intake, and let the engine idle before switching off. And when fitting a new or rebuilt turbo, follow the installation rules — it's the best way to avoid a repeat failure.