Turbochargers are rotating machines that operate at high speeds and temperatures. The most common causes of turbo failure are:

  • Lubrication related problems
  • Ingress of foreign material
  • Extreme operating temperature
  • Workmanship problems/Incorrect fitment

Lack of lubrication:

Lack of proper lubrication can ruin a turbo in a matter of seconds. With speeds of rotation of around 250,000 RPM in some models, all bearings need to receive an oil supply for lubrication and cooling purposes. When this supply either drops too low, is interrupted or is stopped for any reason at all, metal to metal contact first occurs between the bushings and the shaft. This friction will generate enough heat to turn the shaft and / or the axial thrust collar a bluish colour. The contact surface of the axial bearing, thrust collar and / or backplate mating surface will also all show signs of damage. Once the bearings are damaged, the “radial play” of the shaft increases and, instead of rotating in a perfectly circular movement, it starts to orbit. As the main bearing clearance enlarges so the shaft motion becomes greater and leads to accumulated damage in other components such as thrusts and bores which in turn cause even greater shaft motion. When this motion reaches a certain point, the turbine and compressor wheels will rub against their respective housings, damaging the blades and causing the compressor wheel or turbine nut to either move backwards or come off. Once the blades have broken, the subsequent imbalance will lead to shaft breakage.

Lack of lubrication and wear caused by axial play:

If the turbo is taken out of operation as soon as the problem starts, then the damage may not be as extensive as described above. However, given the immediate effect of insufficient lubrication, the user may not be able to react quickly enough to resolve the problem. Damage to the unit normally starts with the bushings and shaft, and then spreads out towards the wheels, causing considerable damage to the turbines, with the vehicle owner observing a higher than usual oil consumption.

Centre housing “cartridge” blocked-up by deposits:

Even “Premium” oil will decompose if the temperatures are high enough during operation or shutdown. When these temperatures reach the centre housing, then deposits will form in its interior. As deposits accumulate, the oil lines (inlet and drainage) through the unit become restricted, raising the temperatures still further and aggravating the problem. Obviously, once the problem has started, it cannot be controlled without the identification and correction of all the causes.

Foreign material in the oil:

Concurrent with the build-up of these deposits in the centre housing, the oil feed and drainage lines become restricted. These deposits migrate to fill much of the oil supply and drainage lines. The granular carbon deposits, now part of the oil supply to the bearings, damage surfaces and increase the play or else accumulate on the bearing surfaces, reducing space for oil films to develop, and plug the bushing lubrication holes. All these deposits alter the bearing system and prevent normal operation (which we call foreign material in the oil). Excessive bearing damage from foreign material in the oil will eventually lead to shaft motion and, finally, to turbocharger failure. Other lubrication problems include low oil pressure, incorrect oil grade or insufficient oil changes, and will eventually affect the turbocharger bearings.
In turn, foreign material from some metal component in the engine interior may contaminate the lubrication oil, causing an erosion effect between the turbocharger internal friction components.

High exhaust temperatures

Generally, the source of heat causing the problem comes from the exhaust gases. High exhaust temperatures can come from incorrect engine air / fuel ratios, timing problems, restricted exhaust systems, malfunctioning of the exhaust oxygen sensor or other engine control system problems. Excessive exhaust temperatures can damage the turbocharger either directly or indirectly.
With direct damage, excessive temperatures overheat the centre housing and turbine housing, decomposing the housing material, passing through the lubrication holes and causing damage to the bushings and bearings. Wheel rub can result, reducing the speed of the shaft and bushings. Meanwhile, the internal eroded housing material (machined) may separate from the housing to become a foreign object in the oil. Turbine housing cracking can also result from excessive temperatures.
Indirect damage from excessive exhaust temperatures occurs when the rotating assembly starts to rotate faster than the rated operating speed for that turbo, as a result of the additional heat energy. If this happens, then the compressor wheel can be destroyed due to the high-stress load. The turbine wheel will break up due to the stress produced by the high temperatures and elevated speed.

Hot shutdowns and continuous overloads:

On many occasions, problems arising in the old turbine are reproduced in the new one. For example: when an engine uses too much fuel, this is synonymous with a breakdown (overload/greater flow rate), due to increased temperature. Consequently, this could cause a very serious breakdown in the turbo and its eventual total destruction. This is due to an excessive flow rate causing an increase in the engine combustion temperature. The pump and injector flow rate must be correct and there should be no exhaust blockages which would lead to a considerable increase in temperature. All the gases would not be correctly exhausted.

By-pass valve cracking:

The breakage of the by-pass valve seat is the result of high temperatures and considerable stress in the exhaust area. One of the most common failures is a loss of vehicle power due to a crack in the by-pass valve seat, leading to a gas leak, whereby part of the exhaust gas is directed through the by-pass valve crack instead of towards the exhaust turbine. Another important point is the actuator (wastegate) on the by-pass valve, which should be correctly adjusted.

Material imbalance due to high temperatures:

Due to exposure to high temperatures, the turbo unit will start to rotate faster than its rated rotational speed, as a result of the additional heat energy. Should this happen, then the compressor wheel could be destroyed due to the continuous overload stress on the engine.
A material imbalance not only damages the turbo but can be transferred to the engine combustion chamber, causing the materials to melt, a possible perforation and seizure of the pistons. If this happens, great care should be taken to remove all the remains of material from the engine and to locate the failure. Otherwise, the failure will re-occur in the new turbo subsequently mounted.
When a foreign body enters the compressor or turbine, it rapidly damages the turbo. This can be located by prior inspection and, on occasions, the material causing the said destruction can be seen. This foreign object that has impacted against the turbine blades, provoking the destruction of the same, also unbalances the rotary assembly affecting the shaft motion in its own housing.
Once the source of the failure has been determined, special care should also be taken to ensure that no material has entered the inlet through the EGR conduits.

Foreign object in the intake compressor wheel:

When the compressor wheel is damaged due to the ingress of some foreign body in the inlet impeller, the damage spreads to the centre housing and bearings, creating total imbalance and even the breakage of the shaft.

Shaft breakage:

An impact to the impeller is a common cause of breakage, causing total turbo imbalance with high vibrations that the shaft is unable to absorb, leading to friction with the turbine and the subsequent breakage of the shaft. Another common cause of breakage is the continuous turbo overloading, causing compressor wheel over-speeding, vibrations and turbo imbalance, ending in the breakage of the shaft. The injection should also be checked in case it is delivering too much fuel, leading to an excessive temperature increase and which could also cause the shaft to break. A sudden seizure of the shaft against its bearings also causes shaft torsion and subsequent breakage.
We are now going to detail a list of possible causes and solutions.
We have taken it for granted that the technician has diagnosed the cause of the problem and that the turbo has been correctly mounted on the vehicle, all the seals have been replaced, the air intake line and the gas exhaust line to the catalytic converter have been thoroughly cleaned or replaced, the cartridge has been pre-lubricated before starting up the engine and that the turbo removed from the vehicle did not have the same problem as the one now occurring.

1- OIL LEAKAGE THROUGH THE INLET PIPE:

Causes:

Too much axial and radial play.

Clogged or obstructed oil drainage from the turbo to the engine.

Excess pressure in the engine crankcase (engine compressions, engine rings).

Obstruction or clogging of the engine crankcase blow-by

Excess engine oil pressure.

Check to see whether it is the result of an accumulation of oil from the previously dismounted turbo.

Check that the engine oil decanter is functioning.

Restriction in the turbo intake line (dirty air filter)

Internal engine problems.

Accumulation of dirt in the cartridge body interior (contaminated and degraded oil or internal deposits)

Turbocharger defect or damaged turbocharger.

2- OIL LEAKAGE THROUGH THE EXHAUST:

Causes:

Too much axial and radial play.

Clogged or obstructed oil drainage from the turbo to the engine.

Excess pressure in the engine crankcase (engine compressions, engine rings).

Obstruction or clogging of the engine crankcase blow-by

Excess engine oil pressure.

Look to see whether it is a result of the accumulation of oil from the previously dismounted turbo.

Check that the engine oil decanter is functioning.

Internal engine problems, ring segments, valve guides (if the turbo exhaust gas intake is damp with oil)

Accumulation of dirt in the cartridge body interior (contaminated and degraded oil or internal deposits)

Turbocharger defect or damaged turbocharger

3- OIL LEAKAGE OUTSIDE THE CARTRIDGE:

Causes:

Inlet and outlet oil seals not hermetic.

Connector housing cracked.

Defective or broken seal between the aluminium plate and the cartridge.

Over temperature in the turbo and deterioration of the o-rings.

Cartridge threaded plugs or machined balls not hermetic.

Cartridge oil drain seals broken or pinched.

Turbo with too much radial or axial play and loss of oil through the screws sealing the crankcases and the housings.

Engine defect, entering exhaust gases with a high quantity of liquid oil into the exhaust housing and leakage of this oil between the cartridge and housing.

Defective turbocharger.

4- ENGINE OIL CONSUMPTION:

Causes:

Check that there are no leaks outside the engine and that the engine is fully hermetic, otherwise correct this first.

Check that points 1, 2 3 above are correct.

Excess engine oil pressure.

Restriction at the air inlet.

Restriction at the turbo oil drainage pipe.

Internal engine problems.

Problems with the engine crankcase blow by.

Check for the correct operation of the vacuum pump or brake depressor.

Housing or cartridge interior with oil with sediments

Damaged turbocharger.

5- BLACK SMOKE FROM THE EXHAUST:

Causes:

Turbo intake pipe restriction.

Engine air intake pipe restriction.

Intercooler obstructed or blocked.

Problems with the vehicle injection system.

Excess fuel injected for the small amount of air delivered.

Restriction in the intake manifold, accumulation of sediments.

Exhaust gas recirculation valve (EGR) functioning incorrectly (open)

Defective air mass measurer or flow meter.

Loss of pressure between the turbo and intake manifold.

Restriction in the exhaust pipe.

Fuel delivery system incorrectly adjusted (engine out of tune)

Internal engine problems.

Accumulation of dirt on the blades of the turbo geometry, preventing correct functioning.

Loss of turbo blow pressure.

Defect in the boost pressure gauge.

Internal turbo defect, turbocharger incorrectly adjusted.

6- WHITE / BLUISH SMOKE FROM THE EXHAUST:

Causes:

Check that points 1, 2 and 4 above are correct.

Check to see whether it is the accumulation of oil from the previously dismounted turbo.

Check that the turbo high-pressure channels and the gas outlet to the catalyst converter are completely clean.

Restriction in the turbo oil drainage pipe.

Restriction in the engine crankcase blow by.

Centre housing interior with oil with sediments.

Internal damage to the engine

Damaged turbocharger.

7- STRANGE CYCLIC NOISES:

Causes:

Rule out any noise coming from the engine.

Check the turbo axial and radial clearance.

Check for possible air leaks and the connection between the engine and turbo.

Check that the seals are correctly placed between them.

Check for possible high-pressure air leaks.

If the turbo has an electronic servo drive, then reprogram this.

Rule out any ingress of foreign material in the exhaust turbine interior and air inlet, and that these are not damaged.

Check the exhaust gas recirculation valve EGR.

Damaged turbocharger.

8- WHISTLING:

Causes:

Check that point 7 above is correct.

Check for possible air leaks in the intercooler and its connections.

Check the inlet manifold gaskets at the engine cylinder head.

Check for cracks in the exhaust pipe.

Check for damage at the inlet compressor wheel.

Check that the shaft is fitted with a nut securing the compressor wheel.
Check whether the exhaust turbine is damaged through the impact of some foreign object entering with the exhaust gases.

Check the rubber sleeves on the turbo to engine connection.

Check that there are no exhaust gas leaks on the turbo or its channels to the exhaust system.

Check the functioning of the exhaust gas recirculation valve EGR

Check for the correct functioning of the pressure adjustment valve.

Check that the intake circuit is airtight.

Check whether the turbo has a waste-gate and, if so, that this opens and closes correctly.

Damaged turbocharger.

9- FAIL SAFE MODE, ACTIVATION OF THE VEHICLE PROTECTION SYSTEM:

Causes:

Reading of failure codes.

Excessive turbo pressure.

Turbo pressure defect.

Defect in the vehicle pressure regulation electro-pneumatic valve.

Defect in the turbo electronic servo drive.

Defect in the turbo pressure sensor (MAP)

Drainage lines to the regulating valve not hermetic.

Fault in one of the onboard electronic devices.

Turbo adjustment failure.

10- ENGINE POWER FAILURE:

Causes:

Ensure that points 7, 8 and 9 above are correct.

Measure the turbo operating pressure in bars, on the high-pressure line and compare with the manufacturer’s data.

Check whether the problem existed before the turbo was replaced or whether the problem occurred when the new one was mounted.

Check that the vehicle exhaust system is not blocked.

Check that the EGR is not continuously open.

Check the parameters for the sensors, actuators and probes, from the engine to the ECU, particularly the pressure gauge, flow metre, Lambda probe, air gauges

Internal engine defect (measure compression)

Turbocharger defected.

11- THE TURBO TAKES A LONG TIME TO REACT AT LOW RPM:

Causes:

Ensure that points 7, 8 and 9 above are correct.

Check whether the turbo pressure relief valve receives sufficient vacuum or electric signal.

Check that the vacuum pump or accumulator delivers sufficient vacuum.

Check whether the vacuum circuit is airtight and that there are no leaks.

Check that the movement of the wastegate or the geometry valve is correct and that there are no abrupt movements.

For variable geometry turbos, check for a vane opening adjustment defect.

For turbos with a waste gate, ensure that this remains closed and idle.

Vehicle defect.

Turbo defect

12- THE TURBO BLOWS TOO MUCH, SENDING A LOT OF PRESSURE:

Causes:

Measure the load pressure and compare with the manufacturer’s data.

Check the pressure gauge parameters.

Ensure that points 9, 10 and 11 above are correct.

Check that the exhaust system is correct and is not empty.

Check that the air intake is the original one for the vehicle.

Check that the turbo has not been tampered with by third parties.

Check that the pipes from the inlet housing to the valve are hermetic.

Check the boost valve adjustment.

Turbo internal adjustment defected

13- A NUMBER OF TURBOS HAVE ALREADY BEEN REPLACED IN THE VEHICLE DUE TO THE SAME PROBLEM:

If the engine is not functioning correctly, then it should not be taken for granted that the fault lies with the turbocharger. It frequently happens that perfectly sound turbochargers are replaced, despite the fact that the fault does not lie with the turbochargers but with the engine.

Only after checking all these points, should the turbocharger be inspected for the presence of defects. Given the fact that the turbocharger components are manufactured in high precision machines with minimum tolerances and the wheels rotate at speeds of up to 300,000 RPM, turbochargers should only be inspected by qualified specialists.

Before manipulating a turbocharger, please consult our Technical Department with regard to each and every doubt you may have.

14- ENGINE OIL FLOW RATE AND PRESSURE:

One of the most common questions asked by technicians with regard to turbo lubrication (being one of the most common failures) is with regard to the oil pressures at the turbo inlet and outlet.

The engine oil pressure is established by the engine manufacturer and the maximum pressure is calibrated by a boost valve. Minimum pressure +/- 1.2 bar at 80 – 100º oil temperature.

The pressure at the oil inlet into the turbo must be +/- 0.4 bar the engine oil pressure (given the fact that the flow of calibrated oil from the bushing exercises an oil restriction).

Whenever a new turbo is installed and the reason for the breakage of the previous turbo is unknown, then it is mandatory to comply with two points. First, the oil pressure should be measured at a lubricant temperature of 80º to 110º centigrade at different engine RPM and this should be compared with the engine manufacturer’s data. Another exceedingly important point is to measure the flow rate of the oil delivered to the turbo and compare this with the manufacturer’s data.

It is possible to have correct oil pressure and an incorrect inlet flow rate, which would lead to the premature breakage of the turbocharger.

Some vehicle manufacturers advise measuring the oil flow rate after flowing through the turbo lubrication pipes before the oil returns again to the engine. This generally ranges between 0.3 to 0.4 l/1 minute.

Whilst other manufacturers take the measurement at the turbocharger oil inlet.

15- REFERENCE BASED TECHNICAL DATA SHEETS:

Currently, together with the material, a series of technical data sheets are supplied based on the product reference. These sheets indicate the most common causes of failure for the reference in question and possible solutions.

It is mandatory to comply with this technical information in order to deal with the material under warranty.

Should it be considered necessary, the Technical Department will request the purchase invoices for the material indicated in the corresponding technical data sheet.

The range of technical data sheets is becoming more comprehensive, day by day. However, there are turbos that still have no technical data sheets. When replacing these turbochargers, the vehicle manufacturer’s technical specifications should be followed.

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