Audi TT

On the 1.8T AUM, oil sludge forms with extended oil change intervals and blocks the oil pump strainer. Early versions had oil supply lines to the turbocharger that were too narrow, promoting turbocharger damage.

Symptoms: Oil pressure loss, engine warning light, rushing engine noises, turbo failure after sludge in oil lines

Sludge build-up blocks the oil supply lines to the 1.8T turbocharger. Older model years had constructively too-narrow lines. The result is turbocharger bearing wear up to total failure.

Symptoms: Blue smoke on acceleration, whistling from the engine bay, oil loss, clear power drop

The camshaft adjuster on the 1.8T tends to coke up with irregular oil changes. The chain tensioner can lose its function. The timing chain then runs too loose, triggering rattling and engine damage.

Symptoms: Rattling on cold start, camshaft adjuster fault code P0011/P0012, power loss

The lower rear wishbone bearing can seize through corrosion on quattro models. In 15 documented cases the wishbone broke and the rear wheel collapsed.

Speedo display, fuel and coolant temperature gauges, and pixel failures in the instrument cluster display are well-known weak points. A full replacement is often the only solution.

On quattro models the Haldex coupling can fail or the control unit can become faulty. Four-wheel drive function is lost; the Haldex fluid must be changed regularly.

On the TT Roadster, the automatic hood mechanism frequently fails due to faulty hydraulic cylinders or worn seals. Window synchronisation and hood rubbers also age badly.

The glass rear window separates from the hood fabric. Additionally, the inner rain gutters can detach, leading to water pooling and damage to control units in the boot.

The two hydraulic cylinders in the B-pillar develop oil leaks through worn seals after a few years. Overhaul of both cylinders costs around €490 at a specialist.