The invention of the turbocharger has paved the way for more powerful cars by making full use of energy that would otherwise be wasted in the car’s exhaust, channeling this back into the engine for improved power. Because the turbocharger has become a very important component of the modern combustion engine found in many cars, turbocharger failure typically means engine failure is not far behind. As such it is imperative that you keep this engine component functioning optimally. One way to do that is by learning the top reasons why turbochargers fail so you’ll have a better grip on how to prevent such failures from ever occurring.
Oil Starvation
Undoubtedly the most common reason for turbocharger failures is the presence of problems in engine lubrication. Simply put, if you have either oil contamination or even oil starvation, then this can lead to turbo failure.
Everyone knows that the engine oil is essentially the life blood of your car. When it comes to the turbocharger, the engine oil is responsible for maintaining the optimum functionality of the main shaft assembly. This assembly is where the turbine wheels and the turbo compressor are mounted. Movements on the main shaft assembly are made possible by a system of bearings. This means that the shaft should have optimum freedom of movement especially when it comes to high-speed rotation. The shaft should never have contact with its housing. As such, the main shaft should be supported by high-pressure oil. This is the very first function of engine oil with respect to the proper functioning of the turbocharger.
The second function is inherent in the effects of high-speed rotation. As the main shaft rotates at a blistering 4,000 rotation per second, this leads to the very rapid generation or buildup of heat. This heat must be conveyed away from the turbocharger’s highly-stressed components so the excessively high temperatures will not soften and damage these components. This is the second function of engine oil relative to the function of the turbocharger. It carries excess heat away from the sensitive components of the turbocharger to keep its structural and functional integrity.
Given that engine oil is important in the friction-less operation of the main shaft and the protection of turbocharger components from excessive heat buildup, one can almost imagine what will happen to the turbocharger if there is insufficient engine oil running through the system. There is no oil to keep the main shaft from getting in contact with the housing. There is also insufficient oil to carry excess heat away from sensitive components. The result is damage or total failure to the turbocharger.
Some of the more common reasons why the turbocharger may have insufficient lubrication can include not observing the correct intervals of changing the oil which can lead to sufficient low oil or the complete absence of oil in the sump. Restricted or broken oil feed pipe can also lead to insufficient lubrication. If the turbocharger has been refitted without adequate priming insufficient oil can also occur. It is also possible that there is sufficient oil but the pressure is so low that it cannot circulate the oil properly. This can happen if the lubrication system has malfunctioned.
It is, thus, imperative that the engine oil be replaced at the vehicle manufacturer’s recommended intervals. If the manual says you should change oil and filter every 7,000 miles, then by all means observe such recommendation. It also helps to use only the engine oil with the correct grade as specified by your vehicle’s manufacturer.
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Oil Contamination
We discussed in the preceding section how oil starvation or insufficient engine oil can damage the turbocharger. The same can be said if the engine oil has been contaminated with debris or any other foreign particle. These contaminants can get in the way of the proper functioning of the engine oil. These particles or contaminants can also get lodged in other parts of the turbocharger such that these affected components will also show signs of poor functioning and eventually damage. More specifically, these contaminants can cause heavy scoring or deep scratches on the surface of the bearings on the main shaft.
There are many reasons why the engine oil can be contaminated. It is possible that the oil filter is of poor quality that it gets easily blocked or damaged. Once the filter is damaged, it can no longer prevent contaminants from being circulated throughout the system. The oil filter may be functioning properly, but if its bypass valve is not, then it is still possible to introduce contaminants into the engine oil. It is also possible that contaminants are inadvertently introduced during the servicing of the engine. If automotive technicians don’t observe strict sterile techniques in handling the engine, they might introduce particles into the system. Severely-degraded lubrication oil can also lead to dirty oil.
If any work is to be performed on the engine care should be observed not to introduce any contaminant into the engine, engine components, or the engine oil itself. It is also critical to use only the parts and lubricants that are approved by the manufacturer for use on your vehicle.
Foreign Object Entry
The turbocharger is essentially composed of two fundamental components: the compressor at the front and the turbine at the back. While the engine and the turbocharger are essentially a closed system, the nature of the work of turbochargers mean they will have significant openings through which debris or foreign objects can enter.
If the foreign object enters the compressor housing, it often comes from the air filter. This can damage the seals and bearings of the turbocharger. Foreign object entry into the compressor section of the turbocharger can be due to damaged or cracked air hoses. It is also possible that the adjustment screws on the hoses are already very brittle because of old age. The incorrect installation of air hoses as well as the inadequate cleaning of such components during the servicing of the turbocharger can also introduce foreign objects into the compressor. To help prevent such occurrences, replacing the air filter and adjustment screws may be needed. Also, the intake hoses should be thoroughly inspected and cleaned.
If it is the turbine that gets damaged because of foreign object entry, it usually means that the problem is originating from the engine itself. It could be due to part of a guide, the valve seat, or even a part of the valve itself. Again, this can damage the bearings as well as the seals of the turbocharger.
Hot Stops
One of the most common, albeit often overlooked causes of turbo failures is what experts call hot stopping or simply hot stops. This is especially true on performance cars.
We already know that during full operation the turbocharger main shaft spins at an amazing speed, creating in the process excessive heat. While adequate lubrication can help dissipate this excess heat away from the more sensitive components of the system, abruptly shutting off the engine while the turbocharger is still at its peak speed will also stop the main shaft from spinning. Unfortunately, because it is still very hot it can rest on one particular area. This can lead to the slight bending of the main shaft. Any change in the alignment of the shaft can lead to an imbalance in the system. Over time this can damage the turbocharger.
It is for this reason that performance cars with turbochargers have to run their engines at idle for several minutes before turning the engine off. This is to allow the turbocharger’s main shaft to reduce its velocity and reduce the heat that it generates. One can easily accomplish this by driving the car at a slower, gentler pace than usual for the remaining 5 minutes of your journey. By the time you arrive at your destination, the turbocharger would have already cooled itself sufficiently that its main shaft will no longer stick to the other components.
Restricted Breathing
There are some vehicles that can have a clogged engine breather system. This simple one-way check valve functions by allowing high-pressure blow-by gases from the crankcase to pass through or escape in a highly controlled manner. Unfortunately, this can get easily clogged over time, leading to an increase in pressure while also restricting flow. This also increases pressure within the turbocharger system, overloading it with oil. In turn, the excess oil also passes through the air intake and exhaust systems of the vehicle resulting in the characteristic blue engine smoke.
The problem is often seen when a new turbocharger is fitted into the engine. Interestingly, the symptoms are only present right after the installation of a new turbo, leading vehicle owners to think that there is something wrong with the newly-installed turbo when in fact they simply forgot to replace the engine breather filter.
The proper functioning of your turbocharger is dependent on a host of factors. Understanding how these factors can impact your turbocharger’s performance can help you avoid costly engine repairs since the turbocharger is an important component of your car’s engine.
Sources:
- How Turbochargers Work – howstuffworks
- Failure Cause Analysis – Turbo Servis
