By Greg Arsenault
You may have read about the most common causes of failures in turbochargers in our most recent newsletter. If you missed the article, you can read it here on our blog.
In this article, we have outlined some additional common failure modes of turbochargers and some tips on how to identify these root causes.
- Lack of oil
- Foreign debris
- Hot shut downs
- Engine tuning
As we look at some additional failure modes, one thing to remember is that there is always evidence of how the failure happened, but sometimes there are multiple factors contributing to the failure.
Lack of oil
If lack of oil is the cause of turbocharger failure, the proof will be fairly straightforward. There will be bluing from excessive heat and galling of the metal. There can also be a transfer of the bearing material onto the shaft.
Foreign debris in the engine is also fairly obvious. At full load turbo speeds, any debris that comes from the air box as a result of a a dirty or missing filter will easily cause a catastrophic failure. There will be noticeable fins broken off of the compressor wheel. If the damage is to the turbine (hot side) of the wheel, barring any excessive bearing clearances, internal engine damage could have occurred. This damage could be in the form of small pieces (including spark plug tips, glow plug tips, pieces of valves) coming through the combustion chamber and into the turbine housing.
Hot shut downs
Hot shut downs are very common. Whether in mountainous areas, hauling a load, or racing, the turbo must be allowed to cool down before shutting off the engine. On my vehicles, I have a pyrometer in the exhaust stream so I can monitor the temperature. There are also aftermarket controllers that keep the engine running until the temperature returns to normal or for a pre-set time interval. If an engine is shut down while hot, the turbo burns off the protective layer of oil that needs to be there for the next start. After four or five times of starting the engine with no oil on the turbo shaft, the damage is done. This damage is compounded if the typical starting mode is “Stomp on the accelerator to hear the turbo !!”
There are many versions and degrees of engine tuning, and not all are detrimental. Some design parameters add a certain amount of safety with no harm to the turbo. There are also many methods of configuring the turbo to tweak the performance, but the law of diminishing returns can set in quickly. Particularly in racing and tractor pulling, where there is so much excess boost pressure, the entire shaft is in effect “pushed” into the thrust bearing, causing excessive end play and wearing out the thrust bearing prematurely.
Bottom line: I would make it a policy never to give a customer a replacement turbo or a refund without first analyzing the failed unit to try to determine the cause of the failure.