guide to four wheel drive
Diesel turbo failures -
|Why is it that petrol
engines seem to last so much longer than the average
answer is anything but simple.
as I may, being simplistic about this issue isn't
going to help.
here I am going to get a bit technical.
if you own or are planning to purchase a turbo-diesel
vehicle understand the pitfalls because some are
am not advocating staying away from diesel engines but rather
an understanding of them will not only prevent huge repair bills
in the future but also enable you to get the long life that
a diesel engine can deliver if treated correctly.
|In 2000 owning a Mercedes 290GDT,
I experienced an engine failure which resulted in a huge learning
curve for me.
It happened on a trip through Johannesburg so I called Steve
from Steve's Auto Clinic in Vanderbijlpark.
| Having more experience with
diesels than anyone else I knew, I felt confident I was in safe
To cut a long story short, a blocked air
filter had caused an excessive exhaust
gas temperature which caused turbo and injector damage.
Two years later, just before this book was published, I purchased
another used 290GDT.
I remember the famous quote, "Those who do not learn from
history are condemned to repeat it". I visited Steve and
again I was on a learning curve.
In just two years problems with damaged turbochargers in thousands
of vehicles had spread from turbo failures to cylinder
heads as well. I wanted to know why?
| Steve uses an effective analogy.
A new vehicle is like a healthy child, fit and energetic.
The child's body is like the vehicle's engine.
Once a child becomes a teenager some begin to smoke, drink or
The body begins a path of deterioration, and becomes diseased.
By forty, the equivalent of forty-thousand kilometers, doctors
says, "Stop smoking!".
So the smoking is stopped.
Is the adult suddenly healthy because a bad habit is kicked?
No. Damage has already been done.
| A new vehicle drives energetically
out of the showroom.
In the case of a diesel engine it is often mishandled recklessly;
like the teenager on a binge.
Driving a turbo-diesel at full power
for long periods, hauling heavy trailers up steep hills at full
hour after hour of speeding down to the coast at 150 kph.
That's how to abuse a turbo-diesel.
These engines are not designed to work this way and it damages
So if you want your vehicle to perform these tasks, buy a petrol!
Petrol car engines are more suitable than diesels for running
at full power
over long periods.
| The advice on fitting a exhaust
gas temperature gauge early in the vehicle's life cannot
be over emphasized.
Drivers inadvertently abusing the engine, driving it in a manner
which over stresses it will be warned by the gauge and buzzer.
This is one of the problems with buying a used turbo-diesel.
Fitting an EGT
gauge after the vehicle has covered 50 000 km is like a forty
year old quitting smoking.
The damage has been done.
Not smoking at all is the most desirable: never abusing the
engine because a gauge is telling you that you are. It's a bit
like a government health warning, but instead it reads, "RUNNING
THIS ENGINE LIKE THIS WILL SERIOUSLY DAMAGE YOUR WEALTH".
| Does the fitting of a EGT
gauge effect the warranty?
No and Yes.
It can in no way have a negative effect on the engine as it
is fitted to the exhaust.
A bloody-minded dealership may claim it has an effect in an
attempt at avoiding a claim, but I was told by Steve that never,
in any one of their nine branches has Steve's Auto Clinic seen
a warranty claim discarded due to an aftermarket fitment of
either an EGT
gauge or intercooler.
| Modern diesels are mostly alloy
head and block.
With cast iron engines high EGT caused turbo and injector damage.
With modem alloy engines high EGT often leads to head, valve
and pre-combustion chamber damage as well.
But how can he be so sure it is high EGT that's causing the
Writers in magazines have come up with other theories, but 99
out of 100 turbo-diesels in for turbo or cylinder head damage
are clearly caused by excessive combustion temperatures.
Heat fatigue shows itself by cracks as the metal changes its
| I was one of the rare 'lucky'
ones as my new G seemed to be in good shape.
| "It happens very rarely
that we see a turbo-diesel
vehicle over 50K with no damage", Steve told me.
He explained that many vehicles without particularly high mileage
arrive for a conversion of some sort.
Sometimes they even try to talk the customer out of it because
a diagnostic test tells a tale that the engine is likely to
have a major failure before 100 000 kms.
While the damage has been done it is lying invisible inside
the engine but it can't be proven without taking the engine
Should they do a modification, even an intercooler,
it is often perceived to have contributed to the failure.
It's a real problem.
| Diesel engines are happiest
when driven on or close to the revs that produce the highest
At higher revs, torque drops off and while power increases so
does the temperature generated.
The result is high fuel consumption and high engine temperatures.
This is why above 140 kph most diesel engines will consume about
as much fuel as a similar petrol vehicle.
At this speed the petrol engine is happiest, revving high and
burning its fuel efficiently, while a diesel is at high-stress,
running hot and burning fuel inefficiently.
| So when considering a new or
used vehicle, think about what kind of driver you are.
If you are towing, buy a petrol.
If you want the economy of diesel, decide now that long stretches
at high speeds are a thing of the past.
If the vehicle is used do a diagnostic test to see if damage
has been done and if its new fit an EGT
gauge without delay and reset the diesel pump on an active dyna
to limit the combustion temperatures before damage is done.
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