EXHAUST MANIFOLD W/ TURBOCHARGER

OUTLINE OF TURBOCHARGER FAILURE

State of Turbocharger Failure Repair

It is well known that turbocharger malfunctions cause many symptoms as shown below. However, the mechanisms resulting in these symptoms that indicate turbocharger malfunctions are not well understood. As a result, many unnecessary turbocharger replacements and other repairs are being performed due to lack of knowledge about the turbocharger and turbocharger failure. Therefore, knowing the facts regarding turbocharger malfunctions is useful for making effective repairs and saving time.

Turbocharger Failure Classification

Symptom		Symptom Description	See page
Noise	Whistling noise	Continuous high pitch noise proportional to engine speed	"NOISE" listed below Flowchart "Turbocharger Noise" for CCo: Click here for DPF: Click here
Noise	Whining noise	Relatively low pitch noise compared to whistling noise
Oil leak	External oil leak	Oil leak on surface of turbocharger visible from outside of turbocharger sub-assembly	"OIL LEAK AND WHITE SMOKE" listed below Flowchart "Turbocharger Oil Leak and White Smoke" for CCo: Click here for DPF: Click here
Oil leak	Internal oil leak	Oil leak from inside of bearing housing to inside of either compressor housing or turbine housing through seal ring
White smoke	Oil smoke	Oil smoke is emitted from exhaust pipe	"OIL LEAK AND WHITE SMOKE" listed below Flowchart "Turbocharger Oil Leak and White Smoke" for CCo: Click here for DPF: Click here
White smoke	Unburned fuel smoke	Unburned fuel smoke is emitted from exhaust pipe
Black smoke		Black smoke is emitted from exhaust pipe	"BLACK SMOKE" listed below Flowchart "Black Smoke Emitted" for CCo: Click here for DPF: Click here
Lack of power or hesitation		Vehicle does not reach target speed	"LACK OF POWER AND HESITATION" listed below Flowchart "Lack of Power or Hesitation" for CCo: Click here for DPF: Click here
		Poor acceleration
		Shock during acceleration
MIL turns on	P0234	Overboost condition	Diagnostic Trouble Code Chart for CCo: Click here for DPF: Click here
	P1251	Overboost condition (too high)
	P0299	Underboost
	P0045	E-VRV failure (not turbocharger failure)	Diagnostic Trouble Code Chart for CCo: Click here for DPF: Click here

Tech Tips

This table shows only typical problems related to the turbocharger sub-assembly.

NOISE

Description
Probable Cause	Probable Failed Component
Turbine shaft imbalance	Turbocharger sub-assembly
Leakage from intake line	Intake line
Gear noise (Mistaken for turbocharger noise)	Balance shaft gear Transmission gear

Tech Tips

It is easy to confirm whether the turbocharger sub-assembly is the cause of the noise or not, and confirming this before inspecting the turbocharger sub-assembly or removing it from the engine is an effective way to reduce troubleshooting time.

Confirm whether the turbocharger sub-assembly is the cause of the noise or not.

*1	Turbocharger Actuator
*a	Disconnect vacuum hose

Disconnect the vacuum hose from the turbocharger actuator.

Check whether the noise is reduced or not compared with the noise under the original conditions.

Reconnect the vacuum hose to the turbocharger actuator.

Result	Cause of Noise
The noise is reduced (or disappears)	Turbocharger sub-assembly
The noise does not change	Not turbocharger sub-assembly (other parts)

Tech Tips

For details regarding the troubleshooting of noise, refer to the following.

for CCo: Click here

for DPF: Click here

OIL LEAK AND WHITE SMOKE

Description
Oil Leak Type	Description	Main Trouble Area
Internal oil leak (White smoke)	Oil leak from bearing housing to either compressor housing (intake side) or turbine housing (exhaust side) through seal rings. This type of oil leak is not visible from outside of turbocharger sub-assembly. If oil leak occurs from turbine side seal, large amount of white smoke will be emitted from exhaust pipe.	Compressor side seal ring Turbine side seal ring Clogging of oil drain Shaft breakage Shaft or bearing seizure Compressor impeller damage
External oil leak	Oil leak from inside of turbocharger sub-assembly to outside of turbocharger sub-assembly. Includes oil leaks visible from outside of turbocharger sub-assembly.	FIPG sealing part Oil pipe flange Oil pipe union Hose connection of intake pipe

*1	Turbine Housing	*2	Seal Ring
*3	Turbine Wheel	*4	Bearing Housing
*5	Oil Inlet	*6	Turbine Shaft
*7	Oil Drain (Outlet)	*8	FIPG Sealing Part
*9	Compressor Impeller	*10	Compressor Housing
*11	Compressor Inlet	-	-
*a	Internal oil leak to turbine housing	*b	Internal oil leak to compressor housing

Tech Tips

Above illustration is an example.
When there is an internal oil leak, white smoke is emitted from the exhaust pipe and oil is consumed excessively. However, the cause of white smoke or excessive oil consumption can vary. Therefore, do not assume that the turbocharger sub-assembly is the cause of the failure when there is white smoke emission or excessive oil consumption.
When there is an external oil leak, the sources of the oil leak are limited to the points mentioned in the table above. If oil leaks from a FIPG sealing part, replace the turbocharger sub-assembly. If oil leaks from an oil pipe flange or a hose connection, do not replace the turbocharger sub-assembly, but confirm and repair the flange or hose.
For details regarding the troubleshooting of oil leaks and white smoke.

for CCo: Click here

for DPF: Click here

BLACK SMOKE

Malfunctions are classified into 2 types as shown below.

Description
Malfunction	Main Fault
Intake air volume shortage	Insufficient mass air flow due to, for example, excessively low boost pressure, which results in fuel injection volume being relatively excessive with respect to mass air flow.
Excessive injection volume	Excessive injection volume or incorrect injection timing due to fuel system trouble.

Main Components Related to Black Smoke

Possible Faulty Component	Main Fault
Turbocharger sub-assembly	Abnormally low boost pressure
Intake system	Leakage between turbocharger sub-assembly and intake manifold
Fuel system	Excessive fuel injection volume Incorrect fuel injection timing
EGR valve	Stuck or does not close completely
Diesel throttle	Stuck or does not move smoothly

Tech Tips

The components listed above are only the main ones. Not all the components potentially related to black smoke are listed. For details regarding the troubleshooting of black smoke.

for CCo: Click here

for DPF: Click here

Relation between Turbocharger and Black Smoke

If the boost pressure is lower than normal due to a turbocharger failure, black smoke may occur due to a lack of mass air flow. However, abnormally low boost pressure can be caused by the failure of various components such as intake lines, the EGR valve, etc. Therefore, do not assume that the turbocharger sub-assembly is the cause of abnormally low boost pressure, but check all the components possibly related to abnormally low boost pressure. Components related to abnormal boost pressure are shown in a chart Click here. For simple and effective troubleshooting, refer to the chart before starting troubleshooting.

LACK OF POWER AND HESITATION

Malfunctions are classified into 2 types as shown below.

Description
Malfunction	Main Fault
Intake air volume shortage	Insufficient mass air flow due to, for example, excessively low boost pressure, which results in fuel injection volume being restricted.
Abnormal injection volume	Abnormal injection volume or timing due to fuel system trouble.

Main Components Related to Lack of Power and Hesitation

Possible Faulty Component	Main Fault
Turbocharger sub-assembly	Abnormal boost pressure VN does not move smoothly
Intake system	Leakage between turbocharger sub-assembly and intake manifold Clogging or blockage of intake line
Fuel system	Abnormal injection volume Incorrect fuel injection timing
EGR valve	Stuck or does not close completely
Diesel throttle	Stuck or does not move smoothly
Exhaust system	Clogging of exhaust line

Tech Tips

The components listed above are only the main ones. Not all the components potentially related to lack of power and hesitation are listed. For details regarding the troubleshooting of lack of power and hesitation.

for CCo: Click here

for DPF: Click here
If obvious malfunction (lack of power) has not been reproduced, perform test driving another vehicle, which is the same model and has the same engine, and compare the engine conditions and performance. If a great difference in engine performance is not present, explain to the customer that lack of power the customer mentioned is not abnormal.

Relation between Turbocharger and Abnormal Boost Pressure

If the boost pressure is lower than normal due to a turbocharger failure, lack of power could occur due to an intake air volume shortage. However, abnormal boost pressure can be caused by the failure of various components such as intake lines, the EGR valve, etc. Therefore, do not assume that the turbocharger is the cause of abnormal boost pressure, but check all the components possibly related to abnormal boost pressure. Components related to abnormal boost pressure are shown in a chart Click here. For simple and effective troubleshooting, refer to the chart before starting troubleshooting.

MIL TURNS ON

If a DTC related to a turbocharger malfunction is stored, refer to the troubleshooting section for each DTC.

BRIEF OUTLINE OF TURBOCHARGER OPERATION AND CONSTRUCTION

A turbocharger is a component used to supply a larger air volume to the cylinders by recovering exhaust gas energy using a turbine coaxially connected to a compressor.

Principle of Turbocharging

Boost pressure is proportional to turbocharger speed, because the intake air is accelerated by centrifugal force generated by the rotation of the compressor and the increased kinetic energy, i.e. the velocity of the intake air, is converted to pressure energy by the diffuser located around the outlet of the compressor impeller. The compressor is driven by the turbine connected coaxially by the turbine shaft. The turbine is driven by exhaust gas energy. Therefore, when the turbocharger begins boosting the intake air, a larger air volume is supplied to the cylinders and more fuel can be injected. As a result, more exhaust energy will be available and the turbocharger boost increases.

*1	Compressor	*2	Turbine
*3	Air Cleaner Assembly	*4	Exhaust Manifold
*5	Intercooler Assembly	*6	Intake Manifold
*7	Diffuser	-	-
*a	See HINT below	*b	Intake Airflow

Tech Tips

*a: If sufficient exhaust gas energy is not available, the turbocharger sub-assembly cannot generate the required boost pressure even when the turbocharger sub-assembly does not have a malfunction.
Considering the fact that the turbocharger sub-assembly is driven by exhaust gas energy, if sufficient exhaust gas is not available due to abnormal injection volume, etc., the required boost pressure will not be available even when the turbocharger sub-assembly does not have a malfunction. Therefore, when boost pressure is abnormally low, checking all the related components using the correct troubleshooting procedure is necessary to perform repairs simply and effectively.

Boost Pressure Control

The amount of energy the turbine can obtain from the exhaust gas is proportional to the expansion ratio, which is defined as the ratio of the turbine inlet exhaust gas pressure to the pressure at the turbine outlet. To control boost pressure, a Variable Nozzle (VN) is used just upstream of the turbine wheel inlet, and controls the expansion ratio. If the VN is closed, the gap between neighboring vanes is narrowed and the turbine inlet exhaust gas pressure, and correspondingly the expansion ratio, increases. Therefore, when the VN is closed, the turbine receives more energy, and the turbine speed and boost pressure increase. On the other hand, if the VN is opened, the turbine inlet exhaust gas pressure decreases, and the turbine speed and boost pressure decrease.

The VN is actuated by a pneumatic actuator. When vacuum pressure is applied to the pneumatic actuator, the actuation rod is moved to close the VN and boost pressure increases. When vacuum pressure is removed from the actuator, the VN opens and the boost pressure decreases.

*1	VN (Variable Nozzle)	*2	Turbine Wheel
*3	Narrow Gap	*4	Wide Gap
*a	VN Closed	*b	VN Open
*c	Exhaust Gas Flow	-	-

Tech Tips

If the VN becomes stuck open, the necessary boost pressure will not be available. If the VN becomes stuck closed, overboost will occur.
If the actuator hose is disconnected, the VN stays in the fully open position, the turbocharger speed does not increase, and sufficient boost pressure is not available. The method of distinguishing turbocharger noise from other types of noise uses this property of the turbocharger.

Mechanical Construction of Turbocharger Sub-assembly

*1	VN Actuator (Pneumatic Actuator)	*2	VN Actuating Rod
*3	VN (Variable Nozzle)	*4	Radial Bearing
*5	Oil Inlet	*6	Thrust Bearing
*7	Compressor Side Seal Ring	*8	Turbine Wheel
*9	Turbine Housing	*10	Compressor Impeller
*11	Compressor Housing	*12	Turbine Shaft
*13	Oil Drain	*14	Bearing Housing
*15	Turbine Side Seal Ring	-	-
*a	See HINT below	*b	See HINT below
*c	See HINT below	-	-
	Exhaust Gas Flow		Intake Air Flow

Tech Tips

Above illustration is an example.
*a: The clearances of the radial bearing and thrust bearing are on the order of 100 μm, and for the accurate measurement of these clearances, an accurate process and accurate tools are essential.
*b: A certain amount of oil mist from PCV gas is contained in the intake air. Therefore, a certain amount of oil at the inlet of the compressor is normal, and is not an oil leak.
*c: The seal rings are C-shaped rings just like piston rings, and have a gap. Therefore, complete sealing is impossible by the seal rings alone. The oil is sealed in with the aid of the boost pressure in the compressor housing, and the exhaust gas pressure in the turbine housing. These pressures prevent oil from exiting the bearing housing through the gap of the seal rings. Therefore, if the turbine shaft is inclined from the horizontal, oil may flow out through the gap of a seal ring. This should not be interpreted as an oil leak due to seal ring failure.

EXHAUST MANIFOLD W/ TURBOCHARGER SYSTEM DESCRIPTION