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Turbocharger Troubleshooting



The following information is for guideline purposes only. Please consult your mechanic for a correct diagnosis of your problem as there may be other contributing factors.

Major problems explained:


Oil at the correct flow rate and pressure will serve to lubricate the thrust and journal bearings, stabilise the rotating shaft and journal bearings and act as a coolant before high turbocharger speeds are reached.

As turbocharger speed and engine load increases so too does the need for oil as a lubricant and coolant. A short delay in the oil reaching the turbo will result in bearing failure.

An oil delay can be recognized by the blueing of the bearings or shaft which alters in colouration in the shaft when exposed to excessive heat.

A lack of lubricating oil will present in a variety of ways:
  • wear on the inside and outside of the diameters of the bearings
  • heat discolouration near the outside diameters of the piston ring carrier at the compressor end
  • the back face and inducer of the compressor wheel shows signs of rubbing.
  • turbine wheel will show similar signs to the compressor wheel
  • one section of the piston rings will show heavy rubbing
  • heat discolouration and rubbing on one area of the face of the thrust ring
  • wear pattern on the thrust bearing

Foreign material or dirt in the lubricating system (Oil Contamination)

Despite popular assumption oil filters are not capable of removing all foreign matter present in dirty or contaminated oil before it reaches the engine or turbocharger bearings. This can result in very expensive problems.

Foreign material or carbon in the lubricating system will cause damage to the bearings and in sufficient amount cause bearing wear and bearing-housing bore wear or even block the internal oil passages of the turbocharger, starving the unit of oil.

This problem is identifiable by

Oil breakdown

Presents two problems 1. Oil deterioration

Oil deterioration is responsible for several problems with diesel engines and turbochargers.

The high temperatures present in a modern diesel engine can cause oils to break down producing carbonaceous materials which stick to the engine rings and other internal parts of the engine and lead to other issues.

As hydrocarbons in the oil mix with oxygen oxidization occurs, producing organic acids of two types: highly corrosive or those with a lower boiling point. If the acids are left to become concentrate they will attack bearings, eventually causing failure.

The remaining oil will respond to the chemicals by forming a sludge which when deposited throughout the engine and allowed to accumulate in the oil systems will pass through the turbocharger. Thrown by a centrifugal force from the rotating shaft against the walls and internal surfaces of the bearing housing the sludge can stick impeding oil flow and resulting in a build-up. Subsequently this will lead to problems with oil drainage, oil leakage at the end of the turbine unit and if let to accumulate on the turbine side will cause a baking to result from the heat and lead to an unbalance in the turbocharger shaft.

2. Outside contamination

Outside contamination is oil deterioration at the fault of agents outside of the turbocharger itself. These may include the by-products of fuel combustions such as ash or soot.

The engine itself may contribute to the break down as tiny metal particles produced by wear and tear will pass through the oil ways in the turbocharger, hastening deterioration. Foreign matter from outside the engine may also play a part as dust and dirt may enter the cylinders through the air intake system.

These problems are usually identifiable through the occurrence of a hard deposit of baked oil built up at the turbine end, seal leakage and sludge, particularly around the bearing housing outlet bore.

Foreign material in exhaust or air-filtration systems

A turbocharger is a precision instrument and the presence of any material in the system is going to damage the turbocharger and may damage the engine.

Damage will be to the compressor wheels which may cause pieces of aluminum to enter the engine and result in engine piston, valve, liner and possible crank-shaft damage.

Should any foreign bodies remain in the system, be they dust or engine valve fragments the turbocharger will suffer a loss of power, damaged wheels, excessive oil usage and may emit black smoke.

Detection of this issue is fairly easy. The turbine or compressor wheel could have sections of a blade(s) broken off and there may be an indentation at the entrance of the compressor cover.

Material and workmanship

Only quality assured materials should be used in turbocharger rebuild and repair. These materials should meet stringent OEM specifications.

It should be noted that replacing a faulty unit with a new one will not always solve the problem. If there is an engine malfunction or an abnormal working condition in the engine the turbocharger will not be able to overcome this problem, it is more likely to emphasize it.

Trouble Shooting

Boost pressure too high Possible issues here are:
  • A fuel system/injection which is defective or has been incorrectly adjusted
  • The boost pressure control valve may have seized closed
  • The boost pressure sensing pipe may be improperly fitted
  • A split in the actuator diaphragm
  • Incorrect wastegate actuator calibration
Blue smoke As already discussed in the ‘main problems’ affecting turbos blue smoke may be an indication of:
  • A dirty air filter system
  • Excessive flow resistance in exhaust system
  • Clog in the oil drain pipe
  • Obstructed crankcase breather
  • Sludge present in the turbocharger centre housing
  • Worn valve guide, piston rings, engine or cylinder liners
  • Dirty compressor
  • Defective sealing on a piston ring
  • Excessive oil levels
  • A gasket sealer used on the oil drain gasket
Black Smoke Indicates:
  • A dirty air filter system
  • Leaking in the suction and pressure line
  • Excessive flow resistance in the exhaust system as a result of leakage upstream of the turbine
  • An incorrectly adjusted fuel system or injection feed
  • Wearing of the valve guide, piston rings, engine or cylinder liners
  • Dirty compressor or charge in air cooler
  • An open or seized boost pressure control swing valve (doesn’t close)
  • Foreign object damage to the compressor or turbine
  • Insufficient oil supply
Compressor/Turbine wheel impact damage Suggests:
  • Defective air filtering system
  • May result in excessive boost pressure
High oil consumption
  • Dirty air filter system
  • Excessive flow resistance in exhaust system
  • Clog in the oil drain pipe
  • Obstruction in the crankcase breather
  • Surge in turbocharger centre housing
  • Wearing in the valve guide, piston rings or cylinder lines
  • Defective sealing on a piston ring
  • Excessive turbocharger bearing clearance
  • Engine oil level too high
Insufficient power or too low boost pressure
  • Dirty air filter system
  • Collapse of induction and intercooler pipes
  • Excessive flow resistance in exhaust system as a result of leakage upstream of the turbine
  • An incorrectly adjusted fuel system
  • Worn valve guide, bearings, cylinder lines or piston rings
  • Restricted intercooler or change in air cooler
  • Boost pressure control swing valve seized in the open position
  • Pipes to actuator and boost control valves fitted incorrectly
  • Turbocharger bearing damage
  • Foreign body damage to the compressor or turbine
Oil leaking from the compressor housing
  • Dirty air filter system
  • Excessive flow resistance in the exhaust system
  • Clogged, leaking or distorted oil drain lines
  • Restricted crankcase ventilation
  • Sludge in turbine centre housing
  • Dirty compressor
  • Defective sealing on a piston ring
  • Engine oil level too high
  • Excessive oil pressure
  • High mileage engine
Oil leaking from the turbine
  • Excessive flow resistance in exhaust system
  • Clogged, leaking or distorted oil drain lines
  • Restricted crankcase ventilation
  • Sludge in turbo centre housing
  • Valve guide, piston rings, engine or cylinder liners wearing
  • Dirty compressor or air charge cooler
  • Defective piston ring seal
  • Damage to the turbocharger bearing
  • High engine oil level
  • Excessive oil pressure
  • High mileage engine
Whistling noise from the engine compartment (under load)
  • Incorrectly fitted or leaking manifold gasket
  • Split or damaged intercooler piping
  • Leaking exhaust manifold gasket
  • Corroded exhaust system
  • Leaking turbine housing mounting flange gasket
  • Exhaust gas leaking between the turbine outlet and exhaust pipe
  • EGR valve seated incorrectly
  • Broken EGR valve piping
  • Worn turbocharger bearings
  • Restricted air filter
  • Imbalance in the turbocharger rotating assembly
  • Damaged compressor wheel inducer blades
  • Damage to turbine wheel assembly


Turbocharger lag:

The delay in boost response between the time the driver accelerates to when the extra power generated by the turbocharger reaches the engine. The severity of the lag is dependant on the size of the turbocharger relative to the actual engine size, turbo efficiency, exhaust back pressure and the engine tuning among other things.

Compressor surge:

Compressor surge occurs when the air pressure after the compressor is higher than the compressor itself can maintain. If the turbo were to operate in surge for any amount of time it would likely result in bearing damage or failure.

The pressure of the air creates a backflow, building pressure and potentially causing a stall.