We’re reminding technicians of top tips on how to ensure their turbo story has a fairy tale ending this Valentine’s Day. As manufacturers build smaller engines but look to maintain performance with higher power delivery, turbochargers have become essential across the market, especially as emissions requirements become more stringent.

Because of this, more turbo-related issues are arriving with technicians, and our product manager Tom Wright has several top tips for best practice to ensure technicians’ close encounters with turbochargers go without a hitch this coming Valentine’s.

“As over 90 percent of turbocharger failures are consequential of other on-vehicle issues, it is essential that the root cause of the problem is identified before fitting a new turbo. This will save time down the line and will prevent any potential issues with the new turbo,” says Wright.

Oil contamination is one of the top reasons for a turbocharger failure – a number of factors can play a part here, so it is essential that the oil system is serviced correctly when fitting a turbocharger to ensure debris from the previous failure does not remain in the system. If the technician doesn’t carry out this step, the new oil can become contaminated also, causing premature turbo failure within minutes, warns Wright.

To avoid failure through insufficient lubrication or oil contamination, oil inlet pipes should be inspected, cleaned or preferably replaced to remove carbon deposits or sludge that could restrict oil flow and/or contaminate the new oil. In addition, in all installations of a turbocharger, priming the oil feed and oil systems is a must, as this will prevent the turbo from instant failure through a lack of lubrication caused by a delay in the delivery of oil.

Modifying driving style is another way to prolong the life of the turbocharger and other vehicle components. This is as simple as allowing time for the engine and turbocharger to warm up before accelerating hard and cool down before switching off. “Operation temperatures will be significantly higher if a turbo has been worked hard and therefore it needs time to cool, as shutting the engine off immediately after a spirited drive can cause the oil to carbonise within the turbo.” Wright adds.

Driving style can also impact the operation of the diesel particulate filters (DPF), which have been compulsory to fit to diesel vehicles since 2009. In turbocharged, diesel-powered vehicles, technicians should advise drivers to perform regular longer journeys to allow DPF regeneration to occur successfully. This can be achieved via a 10-15 minute journey on a motorway at mid-high revs.

A blocked DPF prevents exhaust gas passing through the exhaust system at the required rate. As a result, back pressure and exhaust gas temperatures increase within the turbine housing of the turbocharger, affecting the turbocharger in a number of ways, including problems with efficiencies, boost levels, oil leaks, carbonisation of oil within the turbo and exhaust gas leaks from the turbo. “It’s therefore important that technicians maintaining, and servicing diesel-engine cars pay attention to the condition of the DPF in the event of turbo failure to prevent premature failure of the new turbocharger,” Wright adds.

Just as with the exhaust system, any blockages, restrictions, leaks or contaminants in the air intake system will impact the turbochargers performance and could lead to failure. Wright recommends replacing the air filter on an annual basis to help minimise dirty air passing through the turbo. Contaminated air with pollutants, dust and debris can lead to poor performance and foreign object damage to the compressor. Blocked or restricted filters can lead to incorrect pressures in the compressor housing and therefore oil leaks, which can lead to failure.

At Melett, we’re renowned for producing OE quality products to help the turbo aftermarket produce the highest quality repairs. With an in-house team of highly qualified mechanical engineers, our turbochargers are subject to rigorous engineering and testing processes to ensure they match OE specifications. All our turbochargers are built, balanced and flow tested in the UK to the strictest quality standards to ensure OE performance during operation.

If a vehicle is suffering from rattling or grinding noises during operation, and drivers experience loss of engine power, this could be due to a loose shaft nut on the turbocharger.

In a turbocharger assembly, the shaft nut, also known as a ‘locknut’ or an ‘impeller locknut’, plays a critical role in holding the compressor wheel and rotor group parts to the shaft. To ensure proper functionality, the shaft nut must be tightened using the correct procedure and setting. If there is any kind of resistance or locking up within the rotor, the centrifugal force will continue, and the shaft nut will come loose.

A loose shaft nut can result in catastrophic damage to the compressor wheel within seconds of the turbocharger commencing operation, says Tom Wright, Group Product Manager at Melett.

In the majority of cases, a loose shaft nut is not the primary case of turbocharger failure, and being mindful of this can help identify issues and prevent them from worsening, adds Wright.

Overspeeding causes excessive radial expansion of the impeller wheel but shortens its length. This relaxes the tension on the shaft, which in turn results in loosening of the shaft nut.

Foreign object damage to the compressor or turbine wheel can affect the balance of the assembly. This can cause abrasion with the housing and loosen the shaft nut.

A blockage in the oil feed pipe can cause the bearing system to ‘grab’ onto the shaft, preventing it from rotating, this in turn causes the shaft nut to loosen. What’s more, scoring to bearings, potentially caused by oil contamination, allows the impeller wheel to rub and ‘stall’ against the housing, eventually loosening the shaft nut.

It is also important to note that in most turbochargers, the shaft nut thread direction is opposite to the direction of rotation on the shaft. If the compressor wheel rotates clockwise, the shaft nut threads should be left-handed – if this is not the case, the nut has the potential to become loose during operation.

Our UK-based turbocharger production facility adheres to strict guidelines and processes to ensure that shaft nuts are tightened to the correct tolerances, with each turbo model having its own specific torque settings carried out by its assembly team.

“Detecting the signs that indicate a loose shaft nut can help prevent further damage and reduce the risk of total turbocharger failure,” says Wright.

These include noise from the turbo during operation such as rattling or whining. The compressor blades, when checked, may display chipping or other damage if the shaft nut becomes loose and falls into the compressor wheel inducer. Technicians should also be mindful, Wright advises, of pitting around the compressor inlet or on the compressor blades.

“It’s difficult to prevent turbocharger failure from a loose shaft nut but the key symptoms of the issue can be identified to prevent the issue from worsening. The first step to avoiding loose shaft nut related turbo failure is to keep the engine in good condition and ensure the turbocharger is installed correctly.

“It’s critical that the root cause of a turbo failure is identified, as it can lead to the instant failure of another newly fitted turbo if the incorrect parts aren’t checked and changed. It’s also good practice to always change the oil and oil filter when fitting a turbocharger, using the correct grade as specified by the vehicle manufacturer,” Wright adds.

Click below to view our Loose Shaft Nut failure guide:

For further information on our turbocharger systems, part fitment, technical guides and troubleshooting, explore our website here.

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Effects of foreign object damage on turbochargers laid bare

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If a vehicle is suffering from rattling or grinding noises during operation and drivers experience loss of engine power, this could be due to foreign object damage on the turbocharger.

A foreign object refers to anything that enters the turbocharger through the air or exhaust inlets. When a foreign object enters the turbocharger, its performance will be affected, potentially resulting in considerable damage. Tom Wright, our Product Manager, explains various reasons why this can happen, as well as offering signs to look out for and ways to prevent it.

“It’s critical that technicians pay special attention to the condition of other components within the vehicle to mitigate the risks posed to the turbocharger,” says Wright.

“There are various scenarios that can result in contaminants in the turbocharger air supply, all of which can have devastating effects on the system’s longevity. This includes previous turbocharger failures leaving remnants in the system, debris from engine components or objects left within intakes during regular servicing.”

Causes of foreign object intake can also include faulty or damaged turbo hoses, which inadvertently cause small particles to enter through any gaps in the system.

A turbocharger repair specialist will be able to diagnose foreign object damage if there are visible marks on the compressor or turbine blade, or pitting marks around the compressor inlet and nozzle ring assembly vanes.

If the turbine or compressor blade is found to be damaged, the turbocharger should stop being used immediately, as the rotor balance will be affected, and this could impact its service life.

“To prevent turbo failure from foreign object damage, we recommend that technicians always replace or fully clean intake pipes and check for debris before fitting a replacement turbo,” says Tom Wright. All air hoses should be free from contaminants and blockages. Hoses should also be checked regularly as part of routine turbocharger servicing.

“Technicians should always use the correct air filter suitable for the specific vehicle model, and regularly replace it according to the manufacturer’s recommendations. As with intake pipes and air hoses, following a turbocharger failure, the filter and surrounding intakes should be cleaned to eliminate any debris or fragments that could harm the new turbocharger,” Wright says.

For more information on Melett, including more technical resources, please check out our Turbo Tips

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Expert advice on turbocharger overheating

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If a vehicle is suffering from lack of power, the exhaust is smoking excessively, or there are abnormal whirring noises, it could be because the turbocharger is overheating.

Product Manager, Tom Wright, explains the symptoms, causes, and the steps that vehicle technicians can undertake to prevent an untimely turbocharger failure.

“If a turbocharger is suspected of overheating, it’s critical to undertake a thorough inspection, as it can cause serious issues in the long term,” says Wright. “While it’s not a reversible process, complete failure can be prevented if problems are diagnosed and resolved quickly.”

Turbocharger specialists can establish if a turbocharger has been affected by overheating by conducting a thorough examination of the internal components.

“The heat-soak effect sustained during periods of overheating will cause discolouration to the turbine shaft and bearing housing, as well as internal components, such as the thrust washer and flinger, without necessarily displaying other symptoms of excess wear,” comments Wright.

If the issue is not addressed, this can lead to sections of the turbocharger turbine blades displaying becoming fractured, bent, or damaged. Furthermore, excessive heat can cause carbonisation of the lubricating oil, leading to catastrophic turbocharger failure.

Thankfully, preventing overheating conditions and the resultant strain on a turbocharger is relatively straightforward.

“Vehicle technicians should check that there are no leaks in the cooling lines, and that on diesel-powered vehicles, the DPF is not blocked. Drivers can also take steps to ensure longevity of their car’s turbocharger by giving it time to cool after long journeys,” says Wright.

For more information on us, including technical resources or how to find your nearest turbo specialist, please contact us or visit www.melett.com

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How a blocked diesel particulate filter can damage a turbocharger

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Not enough attention is being paid to the impact of blocked diesel particulate filters (DPFs) on turbochargers, says Tom Wright, our product manager.

If technicians don’t check for a DPF issue when installing a replacement turbo, it could lead to the untimely failure of the new turbo, Wright warns. All diesel-powered vehicles manufactured since late 2009 feature a DPF, which is designed to capture soot and remove it from the exhaust gas as the vehicle is driven. To keep the DPF working efficiently, regeneration processes are employed to burn off any excess soot.

However, there are many factors that can stop these regeneration processes from working effectively, such as the type of fuel and oil used, driving style, vehicle age and mileage. Vehicles that are regularly driven on short or low-speed journeys often don’t reach the required temperatures to activate the regeneration process.

“Blockages prevent exhaust gasses passing through the exhaust system at the required rate, which can cause increased exhaust gas temperature and back pressure,” Wright says. “This can affect the turbocharger in a number of ways, ranging from oil leaks and performance degradation to component failure.”

Increased back pressure forces the exhaust gas through the piston ring seals and into the turbo core assembly (CHRA), leading to excessive temperatures, within the CHRA. This prevents efficient oil cooling within the CHRA, and can even carbonise the oil, restricting oil feeds and causing wear to the bearing systems particularly on the hot side of the turbo. These high temperatures can also lead to failure of the turbine wheel through high cycle fatigue.

A blocked DPF can force exhaust gas through the smallest of gaps, including the clearances in the bearing housing variable nozzle turbine (VNT) lever arm and turbine housing wastegate mechanisms. If this happens, carbon build up can restrict movement of the levers, affecting performance of the turbo. Oil leaks into the compressor housing may also occur as a consequence of exhaust gas forcing its way into the CHRA from the turbine side and forcing oil through the oil seal on the compressor side.

“It is critical that any DPF issues are identified and rectified prior to installing a replacement turbocharger,” says Wright. “Failure to address the original problem means the replacement turbo will be subjected to the same operating environment as the previous unit, and will ultimately suffer the same failure in a significantly shorter amount of time.”

 

For more information on us, including technical resources or how to find your nearest turbo specialist, please visit: https://www.melett.com/technical/