Common causes of Turbocharger failure.
As a turbocharger rebuild centre, we see turbo failures on a daily basis. With 40 years experience working with forced induction we thought we’d share some knowledge and compile a list of the of the top 5 causes that lead to damage or premature failure in a turbo.
Before we dive into that, let’s quickly summarise how a turbo works!
Turbochargers get a lot of hype, they can transform a Naturally Aspirated vehicle into a powerhouse, drastically reduce fuel consumption if tuned accordingly and when looking at the modern car market, are more of a necessity amongst car manufacturers in a bid for optimal performance and MPG.
Turbochargers are essentially just air pumps - a forced induction system that compresses the air that flows into a car's engine via the intake. The advantage of compressing air as it enters the engine is simple; the more air you can squeeze in, the more fuel you can add, resulting in more power and energy potential in each explosion.
To be able to make boost the turbocharger utilises the exhaust gas emitted from the engine to spin the turbine wheel. The turbine wheel spins in a bearing system (journal or ball bearing) and attaches to a compressor wheel which acts as the air pump.
As the turbo spins, generally between 80,000-200,000 rpm, the fresh air on the compressor side is squeezed into the engine resulting in more power capabilities, pops, bangs, wooshes and lots of heat!
Sounds great right, well it is…until it goes wrong!
Much like the moving components of an engine, a turbocharger requires lubrication. Out of all the moving components in the engine, the turbo the fastest moving systems and with such rotational speed comes lots of heat. This means it becomes very reliant on good oil flow and efficient cooling.
So with that being said, lets look at the 5 main causes of turbo failure.
1.Oil starvation
Turbochargers spin at upwards of 100,000 rpm, if there’s oil in the engine, what would cause the turbo to be starved of oil.
As mentioned, the turbo spins incredibly fast, although there may not be a lack of oil in the engine, oil starvation only needs to take place for a fraction of a second in order to cause catastrophic damage to the components when rotating at speeds up to 250,000rpm.
Here’s a few reasons that can lead to, or cause oil starvation:
Lack of oil changes
A turbo is not a sealed system, oil can seep from the bearing housing meaning exhaust gas can get into the oil. If the engine oil isn’t changed frequently enough, carbon deposits from the exhaust can gradually build up in the oil leading to a sludgy resedue. If left untreated, this can reduce the flow of oil inside the turbo increasing the risk of starvation or even completely block the oil feed.
Oil feed line issues
It may seem obvious, but you’d be surprised by the amount of turbochargers we have that suffered oil starvation due to a kinked, damaged or blocked oil feed.
Always ensure your feed line can flow enough oil in the first place, we’d recommend -4 pipework on a ball bearing turbo and -4/-6 on a journal bearing system.
Check for damage, it’s common for oil feeds to be poorly routed across hot components, if the incorrect pipe is fitted it can melt the internals causing it to close up or become blocked. It’s always a good idea to be mindful of your feed line to make sure its integrity isn’t compromised.
Incorrect Fittings
Make sure the oil feed fitting is correct for the turbo. As a rule you should NOT restrict a journal bearing oil feed.
Ball Bearing turbos are usually built with an oil restrictor inside the turbo, however it’s pretty standard for them to have a restrictor style fitting in the feed itself. Secondary restrictors are often used in ball bearing turbos but it is not the correct solution as they can easily become blocked from contamination. A ball bearing turbo generally only requires 40-45psi of oil so an in-line oil pressure regulator is the best solution.
If in doubt check with the turbo manufacturer or your favourite turbo company. ;)
A lot of turbo manufacturers supply their own oil feed fittings on the shelf.
Poor engine building
This isn’t an attack on hobby engine builders, but often is the case that an engine is built and not entirely fit for purpose. For example, a track car that will undoubtedly experience a lot more lateral G-force than that of a road car and will likely require a baffled sump. In a non-turbo application, this can cause a risk of oil starvation to the engine components, but as previously mentioned it only takes a split second for ‘no oil’ to cause serious damage to the turbo. Make sure the entire engine setup is built for purpose. Oil pressure regulators can help keep things in check as too much oil pressure can also cause damage.
We recommend Turbosmart oil pressure regulators, you can find them here >> Turbosmart ORP
2.Excessive Heat
A turbo car will see far greater engine temperatures to that of their naturally aspirated siblings. More power, more violent combustion, more moving components, all make for more heat!
Getting an engine up to temperature is important for many reasons but when the turbo gets too hot things can begin to go wrong. Distortion of components such as the internal heat shield and turbine housing, warping of the turbine wheel, tightness in the bearing or even melting of the components.
Diesel turbine housings are lower grade material and can crack/distort over 650°C. Petrol applications have a few different material options, some of them lower grade which will begin to crack and distort over 800°C and higher spec options that are safe up to around 950°C. High quality turbine wheels (such as the ones we use in our GBT range) are made from Inconel 713 and will start to melt and breakdown at 1020°C.
A few things to keep in mind when dealing with heat:
Protect the engine bay
Keeping air intake temperatures lower will improve power efficiency. Heat blankets, foils, wraps and cooling ducts will ensure the engine bay stays cooler.
If you’re in the market for heat protection, have a browse at some of the offering we have here >> Heat Management
Water/Air Cooling
If your turbo is designed to run water, run water! Air cooled turbos have specifically designed bearing housings with cooling fins. A water cooled turbo is not efficient at removing heat from the turbo without water so make sure it’s connected up.
3.Oil contamination
Over time carbon deposits creep into the oil creating a sludgy abrasive lubricant that can cause premature wear to the turbo components. This wear can lead to excessive movement in the bearing assembly leading to contact of moving components in extreme examples.
Engine fragments or debris that goes unnoticed is a common cause for oil contamination damage. These small metallic particles can be from previous engine failures, general wear and tear or from poorly serviced engines - All resulting in a similar outcome.
Regular oil changes will offer the best counter measure against oil contamination.
4.Foreign object damage
This an obvious one - Foreign object damage can happen to either end of the turbo. Engine fragments such as sparkplug tips can hit the turbine wheel or poor air filter selection can allow large particles to enter the turbo via the compressor wheel. This causes damage to the blades leading to an unbalanced turbo. One of the critical steps when rebuilding a turbo is to properly balance the major components such as the turbine and compressor wheel and complete core assembly. These steps ensure the turbo spins as efficiently as possible with minimal vibration. When these carefully balanced components get damaged, the vibrations from imbalanced components worsen over time leading to serious damage and turbo failure.
Turbine damage
It can be very difficult to inspect or diagnose a damaged turbine wheel in situ, so ensuring your engine is in good health will give you the best chance at mitigating premature damage.
Compressor damage
Spotting compressor wheel damage is often reasonably easy after removing the air filter. If you’re careful, you could even fully inspect this by removing the compressor cover, although it’s worth noting the tolerance around the wheel is often very tight so you must be careful not to damage the blades when attempting this. We do this in a vice with care and attention so bare this in mind if you’re leaning into an engine bay with a grubby mallet…
Investing in a high quality air filer just may save your turbo, or at the very least save you a lot of money when it comes to rebuilding the turbo. We recommend ITG air filters as they seem to give the best protection against intruding particles while offering fantastic performance.
Check out some of our high quality intake & air filter solutions >> Air Filters & Induction Kits
5.Hot stop/Bad driving habbits
Hot stop refers to the method of shutting down your engine without allowing the turbo to cool for a few seconds.
This becomes especially important in performance cars where the user may suffer from a heavy foot during long summer evenings or Sunday morning drives to explore to countryside….
If the engine has gotten hot it’s important to allow the turbo to spin for 30-45 seconds before shutting down to dissipate heat from the core assembly. This will allow the cooling system to do its job by removing heat soak from the turbine and CHRA assembly, preventing 900°C+ from passing into the turbo internals leading to carbonising from heat transfer.
Spirited driving before the engine is warm is a more common contribution to turbo damage and engine failure. Boosting a cold engine wreaks havoc with the internal components, the rate of expansion from a cold engine which is introduced to charged air can lead to cracks! Letting your engine warm up and cool down is an important aspect of ownership, regardless of the vehicle. Whether it’s a diesel work van or a performance track car, a good warm up and cool down will prolong the life of your turbo.
Signs of turbo damage
Diagnosing impending turbo doom can be hard, so here’s a couple of things to look out for.
Blue smoke: Blue smoke is a sign of burning oil, if this is turbo related it will be during idle once the engine has warmed and on overrun after lift off.
Loss of power: A turbo car generates a large portion of its power via the turbo, if this is damaged or worse, has stopped working, you’ll experience a significant loss of oomph.
Oil leaking: Common places to find oil that are a result of a worn or damaged turbo piston rings are in the exhaust and in the intercooler pipework. Although a turbo seal is not complete seal, they should not leak excessively. A small amount of wet is acceptable if the vehicle has been sat, but with regular use, if it’s healthy, it should be dry, assuming the oil drain is clear and the breather system is working correctly, It’s a good idea to check these first.
Whining & whistling: While your turbo should make satisfying whooshy sounds, a constant whistle or whining sound is not the sound of a healthy turbo. This could be anything from damaged bearings to broken compressor blades. If you experience this, it’s a good idea to get the turbo checked before any further damages arise.
Excessive fuel consumption: A turbo vehicle has a precise air fuel mixture that utilises both the engine and the turbo in unison. If the turbo is not working properly, the engine can overcompensate with fuel leading to reduced MPG.
Oil consumption: Without checking the turbo thoroughly, it can be difficult to diagnose worn seals. If you notice an increase in oil consumption on your turbo vehicle, it may be due to worn seals allowing oil to pass into the intake or exhaust system, but it can also be forced to leak oil from other engine related issues.
If you’re in doubt and think your turbo may need attention, feel free to give us a call for free advice, or send your turbo in for a health check and rebuild quote.