Looking after the turbocharger

Service checks

THERE IS no direct maintenance required on a turbocharger, but its longevity is heavily dependent on good engine maintenance. The turbo has only one high speed rotating part: the shaft/turbine/ compressor assembly, so the only parts likely to wear are the shaft bearings and seals. Lubricating oil for the bearings is fed directly from the engine system and then returned into the sump, so by ensuring the engine oil is changed at the prescribed intervals with the correct quality of oil and oil filter, maximum bearing life can be expected from the turbo.

A slight amount of engine oil will seep from the turbo’s shaft bearings, increasing as the bearings wear. The leaked oil gets into the air passing through the compressor and is carried through to the intercooler where it collects in the bottom. If this oil builds up sufficiently, it can be carried through to the engine, causing smoke and efficiency loss. This is why the maintenance schedule requires the intercooler to be flushed out occasionally, and it’s a job that’s often missed or ignored.

The mechanisms controlling boost pressure: the wastegate system or the later variable vane mechanism, are the most likely sources of faults and running problems. The mechanisms of both types can stick, and while the wastegate type can be fairly easily accessed and freed, the later variable vane mechanism is not a serviceable, or reachable, item.

The turbo, intercooler and engine air inlet manifold are connected by steel pipes and

Talking to your garage

THIS MAINLY concerns the later vehicles with variable vane turbochargers controlled by the electronic engine management system, though the basic essentials of giving clear and concise information to the garage apply to any Land Rover issue.

Make a note of any fault messages and warning lights that appear on the dashboard, together with the driving conditions (accelerating, braking, under load, coasting, decelerating, speed, gear position, etc), and whether the engine was at running temperature or cold. Note any noises and changes in performance such as poor acceleration, smoke, hesitancy. Mark up any other electrical failures or changes at the time of the problem. Also inform the garage of any recent work done to the vehicle, especially involving disconnection of the battery, or dismantling of the induction or exhaust system and disconnection of sensors. Write all this down in logical order and give the list to the garage. Some of the information will be irrelevant, but other points will help the diagnosis.

flexible hoses held with compression clips. These need to be checked at service intervals to ensure the clips are tight enough to prevent joint leakage, and that none of the hoses are split, holed, or likely to become that way through chaffing against other components. Blockages caused by kinked hoses are easy to spot, but whenever hoses are disconnected, check inside for delaminated material that can block or restrict the air flow. It’s worth renewing the hoses after say, 100,000 miles, depending on use.

A partially-blocked air filter will restrict the flow of air into the engine and reduce efficiency and also induce oil leakage from the turbo’s bearing seals so, as always, regular air filter changes are important. A poor quality or misaligned air filter will allow abrasive dust to erode the compressor rotor.

If you notice the impeller locknut is loose, take the unit for inspection and repair. A loose locknut is rare, but typically caused by worn bearings allowing the impellor to rub on the housing. There is a set procedure for re-tightening, but first the cause needs to be established. Obviously, break up of a loose compressor rotor will result in fragments entering and damaging the engine.

Lubrication

Oil is retained in the bearings by seals. If the shaft seals are worn, or distended by shaft movement in worn bearings, oil can seep out. At idle speed, when the engine is drawing air in and the turbo is under light load, the air suction from the engine can draw oil through the worn seals into the compressor section, and this situation will be worse with an old, blocked air filter fitted.

Driving tips

It’s never a good idea to rev an engine straight from starting because oil pressure needs to build up and the oil to circulate, and it needs to reach the turbo. Engine oil not only lubricates the turbo’s shaft bearings, it also cools them, so after a long hard climb, or heavy towing, switching the engine off suddenly can cause static oil in the bearings to bake or carbonise. The residue then restricts subsequent oil flow through the bearings, affecting lubrication and cooling. It’s best to leave the engine idling for a few seconds, before switching off, perhaps while removing your seat belt.

A whistling noise heard from the engine bay is often assumed to be a turbo problem. Certainly it needs checking because this could be the sound of very worn turbo bearings or shaft misalignment. But it is far more likely to be the sound of air or gas leaks in the exhaust and induction piping, especially from split or loose hoses. On Td5 engines, check the exhaust manifold where it bolts to the engine for signs of soot from gas leaks where the manifold has warped – it’s common, and not related to the turbo.