– Diesel turbo failures –
Why is it that petrol engines seem to last so much longer than the average turbo-diesel?
The answer is anything but simple.
Try as I may, being simplistic about this issue isn’t going to help.
So here I am going to get a bit technical.
So, if you own or are planning to purchase a turbo-diesel vehicle understand the pitfalls because some are very costly.

I 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 hands.
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 both.
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 power, 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 them!
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 damage?
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 form.
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 apart.
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 torque.
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.