damage brochure mahle original turbochargers

7/30/2019 Damage Brochure MAHLE Original Turbochargers

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AFTERMARKETTechnical information

TURBOCHARGER:DAMAGE PROFILES, CAUSES, AND PREVENTION


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Table of contents

1 Preface

2 Inadequate lubrication

3 Contaminated oil

4 Oil leakage at turbocharger

5 Foreign object damage

6 Damage due to excessive exhaust temperatures

7 Overspeeding

4

6

8

10

12

13

14


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Preface

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1 Preface

MAHLE s one of the most mpor tant development partners and man-

ufacturers of engne components and systems as well as filter systems

n the automotve ndustry. The engneers at MAHLE develop products

of the hghest qualty throughout the world n conjuncton wth engne

and vehcle manufacturers. The same hgh qualty gudelnes are also

appled for the spare parts n the aftermarket.

Numerous checks durng and after producton ensure the hgh qualty

level of MAHLE products. If falures occur n practcal operaton, the

causes are mostly found n the engne envronment.

TURBOCHARGERTHE FUNCTION

Turbochargers are used to enhance the performance and optmse the

combuston. To acheve good and complete combuston n the engne,

a mxture rato of 1 kg fuel and approxmately 15 kg ar s necessary

(stochometrc fuel rato). Ths ar volume corresponds to about 11 m.

Durng turbochargng, the densty of the ntake ar s elevated and the

ar volume ncreased.

The volumetrc eicency and thus the eicency of the combuston

engne are sgnficantly mproved by means of turbochargng. In add-

ton, the torque can be ncreased consderably, whch n turn serves

to enhance the performance. The turbocharged engne wth the same

power output as a naturally asprated engne can therefore be desgned

wth a smaller dsplacement and hence lower weght (downszng).


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Preface

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This brochure summarises typical damage scenarios and sheds light

on their possible causes. The information is supplemented by tips on

how to avoid such damage in the future.

In this way, we aim to make it easier for repair shops and engine

reconditioners to troubleshoot potential damage causes and ensure

appropriate engine repair, which in turn is necessary for the long and

reliable functioning of our products and hence the entire engine.


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Fig. 1

Impeller after contact with housing

Preface

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2 Inadequate lubrication

Inadequate lubrcaton s one o the most requent causes or turbo-

chargers to al. I the turbocharger s not suicently suppled wth ol,

damage wll occur wthn a very short tme. Ths s due to the very hgh

speeds o the turbocharger.

EFFECTS

The mpeller and turbne wheel can strke the turbocharger housng

on account o bearng damage (Fig. 1). Ths can be dscerned rom

wear marks on the housng (Fig. 2).

I the turbocharger boost pressure s too low, the engne wll not

perorm properly: the rotatng assembly no longer reaches themaxmum speed and can no longer buld up the ull boost pressure

as a result. The reason or ths s the mxed rcton caused by the

nadequate lubrcaton.

The exhaust system emts black smoke. These are the efects o the

engne not beng suppled wth enough ar and a correspondngly

too rch uel-ar mxture.

The shat shank exhbts clear dscoloraton (Fig. 3), whch arses

rom rcton and the resultant hgh temperatures between the shat

and the bearngs. The cause o ths s nadequate lubrcaton. I

the temperature exceeds a certan level, the bearng materal wll

become deposted on the shat (Fig. 4) or the bushng mght even

become completely used to the shat.

A broken shat shank (Fig. 5) s the result o operatng the turbo-

charger or a prolonged tme wthout enough ol. The shat materal

can th s b rn o t and break


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Fig. 5

Broken shaft shank

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CAUSES

The ol level n the engne s generally too low. As a result, not only

the engne but also the turbocharger receves an nadequate ol

lubrcaton and ol coolng.

The ol used s not suicently temperature-resstant, leadng to

ncreased carbonsaton. Ths mght cause problems: the ol supply

lne o the turbocharger and the ol bores n the bearng housng o

the turbocharger can become carbonsed.

I the engne was turned of whle hot, the ol supply lne can become

carbonsed, whch means the turbocharger s no longer suppled

wth enough ol. I the cold engne was brought to hgh speeds mmedately ater the

start, there s a rsk that the ol supply n the turbocharger s not yet

suicent and hence the ol film n the turbocharger tears of.

I oregn substances make t n the ol crcut, such as drt or sealng

resdues, the ol supply lne o the turbocharger and/or the bearng

housng o the turbocharger mght be clogged.

I the vscosty o the ol s too hgh, the ol transport to the bear-

ng ponts s delayed, whch means that the tmely ol supply o the

turbocharger s not ensured. At too low a vscosty, the carryng

capacty o the ol s too low, whch can lead to mxed rcton.

I the engne s operated wth bodesel or vegetable ol, there s a

rsk o the engne ol gellng. Ths ncreases the vscosty o the ol

and t can no longer be transported through the thn ol bores n the

turbocharger.

Th t th b h l b ht b


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Fig. 1

Grooves in the radial bearing

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3 Contaminated oil

Dirt, soot, uel, water, combustion residues, or metal abrasion can

contaminate the oil. Even the smallest particles in the oil can cause

serious damage to the turbocharger due to its extremely high speeds.

EFFECTS

The smallest oreign substances in the oil cause grooves in the

bushings (Fig. 1). The piston rings in the turbocharger can undergo

serious wear. As worn piston rings can no longer adequately seal

the turbocharger, the oil enters the turbine side, which can be dis-

cerned by increased oil consumption.

The bearing play o the rotating assembly increases due to the wornbushings. This leads to wobbling movements and causes the tur-

bine wheel or impeller to come into contact with the housing (Fig. 2).

The shat might subsequently break of.

The bearing collar, i.e. the thrust washer o the axial bearing, exhibits

grooves.

Grooves or retting marks are discernible in the ax ial bearing.

Due to a blocked oil return line, the oil in the turbocharger can no

longer flow of and is instead orced out to the compressor and

turbine side. On the turbine side, the oil might then burn onto the

shat and coke (Fig. 3). Owing to the oil carbon layer, the bearing

housing and the piston rings might be significantly worn of as a

consequence.

The shat o the turbocharger shows clear signs o wear at the bear-

ing points (Fig. 4).


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Fig. 4

Clear signs of wear on the shaft at the bearing point

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REMEDY/PREVENTION

The maintenance intervals according to the manufacturer's recom-

mendations should always be complied with.

Only high-quality oil filters specified for the respective vehicle should

be installed.

Only engine oils specified by the vehicle or engine manufacturer may

be used.

A new charge air cooler and air filter should always be installed when

replacing the turbocharger. In addition, an oil change including oil

filter replacement must be carried out.

The air filter housing and charge air line should be cleaned bysuction.


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Fig. 1

Carbonised oil return line

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4 Oil leakage at turbocharger

If the engine shows signs of increased oil consumption and emits blue

smoke, it is imperative that the turbocharger is included in the cause

analysis. Important: Oil is forced out of the housing from a turbocharger

only if divergent operating conditions predominate in its environment.

EFFECTS

Oil is forced out of the turbine or compressor side of the turbocharger.

Blue smoke is emitted from the exhaust system.

Engine oil has accumulated in the intake section and charge air

cooler.

The engine experiences a power loss. Uncontrolled overspeeds resulting in the engine (so-called rising)

due to the engine oil accumulating in the charge air cooler, which is

blown into the intake of the engine and combusted.

The guide vanes might be coked in a VTG turbocharger.

CAUSES

If the oil return line of the turbocharger is clogged (Fig. 1) or con-

stricted by a kink, the oil can no longer flow out of the turbocharger

(Fig. 2, diagram B). A possible cause for clogged oil return lines is

the coking of the return line, which might be due to missing heat

shields, a poorly routed return line, heat soak, inadequate oil quality,

or the use of liquid sealants. As the turbocharger is still supplied

with oil from the engine circuit, the oil then escapes to the turbine or

compressor side.

If th i i li d ith t h il th il l fl


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REMEDY/PREVENTION

The engine must only be filled to the specified maximum oil level.

Only engine oils specified by the vehicle or engine manufacturer may

be used.

The oil return line must be routed exactly as in the original state. In

addition, it must be ensured that all heat shields are attached.

The oil return line and the connections to the crankcase must be

checked for continuity. We generally recommend replacing the line

and the connecting piece.

The crankcase ventilation must be checked and replaced, if

necessary. The piston and piston rings must be checked for wear and replaced,

if necessary.

A new charge air cooler and air filter should always be installed when

replacing the turbocharger. In addition, an oil change including oil

filter replacement must be carried out.


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Fig. 1

Damaged air guide plates of the VTG unit

Fig. 2

Impeller damaged by foreign substances

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5 Foreign object damage

I oreign substances, such as dust, sand, screws, parts o piston

rings or valves, and sediments, enter on the intake or exhaust side,

this will usually lead to total ailure o the turbocharger due to the

very high speeds. Damage to the charge air cooler might also be the

consequence.

EFFECTS

On account o previous damage, oreign substances rom the

engine or the exhaust maniold can damage the gas entry edges o

the turbine wheel.

The air guide plates o the VTG unit are damaged and bent (Fig. 1),leading to a significant power loss.

Foreign substances in the intake air result in damage to the impeller

(Fig. 2). The vanes might become completely worn as a result. In

addition, the intake passage o the compressor housing might be

damaged (Fig. 3).

The impeller might be damaged by condensation rozen in the intake

section. Damage to just one vane is characteristic o this cause:

owing to the high speeds, the ice particles burst when encountering

the first vane, with no other vanes being damaged (Fig. 4).

CAUSES

I a valve is torn of or the piston rings racture, or example, these

parts come into contact with the guide vanes o the VTG unit and the

turbine wheel via the exhaust maniold.

B th l k i th i t k ti d t i t d d ti


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Fig. 1

Crack in the turbine housing

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Each turbocharger s desgned or only a defined temperature range.

I ths range s exceeded, the turbocharger can al ater just a ew

seconds.

EFFECTS

Cracks n the housng o the turbocharger (Fig. 1).

Ol lnes can become coked: I the supply lne s carbonsed, the

turbocharger wll not be suicently suppled wth ol. I the return lne

becomes coked, the ol can no longer flow of and ol s orced out

o the turbocharger (see also secton 4 Ol leakage at turbocharger

on page 10).

CAUSES

The temperature level has changed due to tunng.

Combuston aults have occurred n the engne.

The engne was turned of whle stll hot.

REMEDY/PREVENTION

The turbocharger may only be nstalled n the specfied vehcles.

The turbocharger may only be nstalled and operated n the orgnal

state as suppled. Techncal modficatons are not permtted.

The engne must always be cooled down at moderate speeds ater

hgh stress, such as drvng at ull load.

6 Damage due to excessive

exhaust temperatures


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Fig. 1

Dents on the rear of the impeller

7 Overspeeding

The parts instal led in the turbocharger are designed for a defined

speed range. If this range is exceeded, major turbocharger damage

can occur within seconds.

EFFECTS

Small dents can be seen on the rear of the impeller (Fig. 1). The

material (mostly aluminium) has deformed plastically due to high

centrifugal forces at overspeeds. It begins to flow and the outer

diameter increases.

If the speeds increase further, the impeller can come into contact

with the housing and/or break apart (Fig. 2).

CAUSES

The maximum permissible speed of the turbocharger was exceeded

due to tuning.

The VTG air guide plates become blocked in the position for

low speeds due to carbonisation. If the engine speeds are then

increased, the turbocharger enters the overspeed range.

The pneumatic or electric control is defective or leaking.

REMEDY/PREVENTION

The turbocharger must always be left in the original state as supplied.

The turbocharger may only be installed in the specified vehicles.

The engine must always be cooled down at moderate speeds after

high stress, such as driving at full load.

O l i il ifi d b th hi l i f t

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