Can a DPF cause turbocharger failure?

There are many technical documents relating to how a faulty turbo can lead to Diesel Particulate Filter damage. However, the DPF is responsible for more turbo related failures than you might think. Antony Collins, Technical Specialist at Melett, explores what effect a blocked DPF can have on a turbocharger.

DPF’s, first introduced in January 2005 with the Euro 4 emission standard, concentrated on cleaning up emissions from diesel cars, especially reducing Particulate Matter. Reducing PM from
the combustion process to this level was not technically possible, so this meant diesel vehicles after September 2009 were fitted with a DPF to capture soot and other harmful particles, preventing them entering the atmosphere.

A DPF can remove around 85% of the particulates from the exhaust gas. A blocked DPF, however, will not work correctly to achieve this.



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,
causing problems with efficiency, oil leaks, carbonisation of oil within the turbo and exhaust gas leaks from the turbo. Drivers may experience turbo lag or over boost of the turbo.


• Discolouration of parts within the core assembly (CHRA), usually with evidence that the heat is transferring through the CHRA from the turbine side. The excessive temperature is caused by
back pressure forcing the exhaust gas through the piston ring seals and into the CHRA. The high temperature exhaust gas can prevent efficient oil cooling within the CHRA and carbonise the oil, restricting oil feeds and causing wear to the bearing systems. This type of failure can often be mistaken as a lack of lubrication or contaminated oil.

• Carbon build-up in the turbine side piston ring groove caused by the increased exhaust gas temperatures.

• Carbon build up in the turbine housing wastegate and VNT mechanism will restrict movement of the levers and affect performance of the turbo. In some cases, soot build up can be seen on the back face of the seal plate where the exhaust gas has been forced through.

• Oil leaks into the compressor housing can occur due to exhaust gas forcing its way into the CHRA from the turbine side and forcing oil through the oil seal on the compressor side.

• Turbine wheel failure through high cycle fatigue, caused by temperature increase.

It is essential to identify the failure mode and determine whether a DPF related issue is the root cause. If the entire rotor assembly is OK and there are signs of overheating at the turbine side of the CHRA, the failure is likely to be caused by excessive exhaust gas temperatures, indicating a blocked DPF.

To help prevent turbo failure caused by DPFs:


• Determine whether the DPF is blocked.

• Contact a DPF specialist for advice.

• Replace the DPF with a high-quality replacement.

• If the DPF is blocked, always replace the turbocharger CHRA to prevent possible oil leaks.

• Check the actuator achieves its full range of movement, particularly if electronic, as internal components could be worn.

One final consideration, it takes time for a DPF to block, sometimes years. Once blocked though, turbo failure can occur very quickly. If you don’t check for a DPF issue when installing a replacement turbo, there is a very high chance the replacement turbo will suffer the same failure, as it will be subject to the same operating environment as the previous unit.

Melett Latest Article in Technician July 2018 –

Why a Visual Comparison of Turbo Products can be Unreliable

It is not uncommon for some turbocharger repairers to compare turbo products visually and assume that if the products look the same, then the products have been manufactured to the same standards. Here, we offer  advice as to why  visual comparison cannot be relied upon when considering the quality of products.

When new turbocharger components are under development, the cost of producing new tooling for that component can be very expensive. To aid development of components, manufacturers will often source  parts from foundries that already have existing tooling for those components.

For such high-volume turbo products, foundries will develop their own tooling, enabling them to sell their castings to many different manufacturers. This enables the manufacturers to price their parts more competitively as they have saved in tooling costs.

So, what are the differences between these ‘quality’ turbo products?

Even in cases where the same tooling is used, a foundry will produce castings to the specifications of their individual customers. These requirements can include completely different material specifications. Different post-casting processes (such as heat treatments or surface treatments) and different ‘pass/ fail’ quality criteria.

For example, quality manufacturers, including Melett, specify 100% high pressure oil/water gallery testing on all bearing housings; an extra cost which some lower cost manufacturers often prefer not to pay. Quality manufacturers may also specify strict dimensional controls on turbine wheel castings to ensure the balance quality of the end product. This means that the foundry typically incurs extra costs as it has a higher scrappage rate of substandard parts.

Another difference can be the tolerance levels requested on the design drawings. High tolerances on drawings mean more parts do not meet strict machining criteria. This again increases scrappage rates. For instance, for every 100 pieces produced, a manufacturer may have as many as 30 out of tolerance parts. This means that these 30 pieces will be scrapped and the production costs of these added to the overall price of the remaining 70 pieces.

To reduce such out of tolerance failures, some manufacturers will accept tolerance changes which reduce the machining quality required. In the above example but with lower tolerances, 85 items of the 100 pieces produced could meet the revised criteria, with only 15 pieces scrapped. Therefore, whilst the cost of the parts may have dropped, the component quality will also have reduced.


A low quality BV50 thrust bearing (left) and a Melett BV50 thrust bearing (right).

More than meets the eye

When comparing a high quality product with a lower cost alternative, it is risky to assume that they are equivalent parts, even if they look  the same. As explained above, it is important to consider more than just the visual appearance of a component. If it appears to be cheap, it can be worth asking; ‘how do the manufacturers make this product so cheap?’ and ‘what corners may have been cut in terms of quality to achieve that low cost?’

More Examples

The UK government’s planned 2040 petrol and diesel vehicle ban

2040 vehicle ban; emissions

The UK government’s plan to ban the sales of new petrol and diesel vehicles by 2040 dominated the news and media headlines this summer.

Commentators speculated on the death of the internal combustion engine. Around the country drivers were contemplating the potential reduced value of their vehicles.

The move to improve air quality is part of the government’s ‘UK Plan for Tackling Roadside Nitrogen Dioxide Concentrations’. Next year the government will publish a further comprehensive ‘Clean Air Strategy’, addressing how they plan to reduce other sources of air pollution.

What does the 2040 vehicle ban really mean?

Whilst the headlines may lead people to believe that 2040 will see all petrol and diesel cars and vans removed from the streets; the reality is that the government ban only covers the sale of NEW petrol or diesel models. This means that conventional petrol or diesel cars and vans bought and on the road before this deadline, will still be able to be used.

Similarly, Hybrid vehicles (which combine a conventional engine with an electric motor) will still be sold after 2040. So this ban won’t mean the end of new petrol- or diesel- engine models in car showrooms and forecourts of van dealers.

The rise of alternate fuelled vehicles

22 years can be a long time in motor vehicle technology. Looking at the difference between vehicles from 1995 and now, its easy to anticipate that technology developments will accelerate even faster in the future. It’s therefore likely that things will be very different in 2040, compared to 2017 – without any government intervention.

Figures released from The Society of Motor Manufacturers and Traders (SMMT) early this year, showed that registrations of alternatively fuelled vehicles (AFVs) have grown more than threefold over the past five years.

This includes; hybrids, plug-in hybrids, plus fully electric and hydrogen powered vehicles. The choice for customers is also expanding. Currently over 80 different alternatively fuelled cars and vans are available to British buyers, from city cars to SUVs, saloons, and sports cars.

Whilst demand for AFVs is growing, it is clearly still at a low level compared to petrol and diesel vehicles. Customer apprehension is currently restricting further growth. Factors for concern include; the high price of AFVs compared to their conventional counterparts, the restricted travel range of fully electric vehicles before the need to recharge, and the lack of available infrastructure (hydrogen fuel stations and electric charging points). These all prey on the minds of car buyers.

Improvements in all these factors will no doubt be achieved in future years, leading to a greater adoption of AFVs. However getting the public onside is not the only challenge.

Some bumps in the road to a green future

If the government go ahead with their plans for 2040, experts have warned that a large-scale change in the UK to electric power would place unprecedented strains on the National Grid. It is reported that peak demand for electricity could increase by 50%, against a current peak of 61 GW.

The extra electricity needed would require the equivalent total power output of ten new Hinckley Point C nuclear power stations. This would cost around £200 Bn, based on current cost estimates for the construction of Hinckley Point.

Currently electric vehicles account for just 4% of car sales. Concerns have also been raised about whether Britain will have enough charging points for the new generation of cars. Today there are 13,000 electric vehicle charging points in publicly accessible locations. It is predicted that the number of such points will increase to 80,000 by 2025.

Many charging points will be on the car parks of supermarkets, railway stations and shopping centres. But, a large number  will be required in domestic streets. It is currently unclear as to who would foot the bill for such infrastructure.

Another issue is likely to be the lack of the rare minerals required for the large-scale future production of batteries. Battery makers are struggling to secure supplies of the key ingredients required in these large power packs; mainly cobalt and lithium. Currently the plans of both battery and vehicle manufacturers rest on the mining sector finding more deposits of these precious minerals.

The impact on the turbo aftermarket

It’s difficult to accurately predict the likely impact on the turbo aftermarket. Working on the basis that conventional petrol and diesel vehicles could be on sale up to 2039, and assuming an average 15-year vehicle lifespan, conventional vehicles would still be around into the 2050’s.

Also, if hybrids using turbo assisted internal combustion engines alongside electric motors remain popular, the need for turbo replacement / repairs is highly likely to continue towards the 22nd century.

The adoption of hydrogen internal combustion engines could be the ideal solution from many perspectives. Hydrogen engines burn fuel in the same manner that petrol engines do, and require relatively minor engineering design modifications from current engines. They are also refuelled in similarly to current petrol / diesel vehicles, so it would seem relatively simple to adapt the existing fuel station infrastructure.

Typically, hydrogen engines are designed to use about twice as much air to enable complete combustion. Unfortunately, this reduces the engine’s power output to about half that of a similarly sized petrol engine. To make up for the power loss, hydrogen engines are usually equipped with turbochargers or superchargers.

So, whilst it’s tough to precisely forecast exactly what will happen, there are enough indications to show that the turbo aftermarket should remain healthy for many years to come.

Also see; How the internal combustion engine is being refined in 2017.

Defining Remanufacturing

caliper measurement remanufacturing

Whilst opinion about remanufacturing has changed significantly in recent years, there remains a common misconception that remanufacturing within the automotive industry belongs in the same category as ‘reconditioning’ and ‘repair’. Here, we look at what remanufacturing really means.

What is remanufacturing?

“Remanufacturing is the process of returning a used product to at least its original performance with a warranty that is equivalent to or better than that of the newly manufactured product.”

The Centre for Remanufacturing & Reuse (CRR)


The process involved in the remanufacturing of automotive parts is very similar to that involved in the production of the original component. The only real difference is that remanufacturing involves the restoration of a used component to its original condition, rather than the production of a brand-new part.

Often remanufacturing (or reman) means bringing the products back to the OE specification, using genuine parts and test equipment. At times aftermarket design improvements mean that remanufactured parts often outperform the OE originals as any design defects can be engineered out.

From a customer viewpoint, the reman product can be considered the same as a new product, providing a more attractively priced alternative to the original. In the case of engines, the price difference between a new and a reman engine can be substantial (with reman costs typically 20% – 30% lower than new).

The benefits of remanufacturing parts

In all instances, remanufactured parts can provide value for money and will perform in the same way as the original parts and last just as long. They provide the end user with an economical and safe way to maintain their vehicle on the road.

Remanufacturing also provides additional benefits on a wider scale. The CRR reports the benefits of reman to the environment can include;
Reduced raw material consumption – as reman preserves much of the material in the original product, less raw material is used than in the manufacture of new products. This is particularly beneficial where the product contains critical raw materials where there is a risk of limited supplies.
Reduced energy consumption & CO2 emissions – by limiting the amount of raw material extracted/recycled and the manufacturing of new components, remanufacturing typically uses less energy than manufacturing a new product; (around 80% less energy used versus production of new parts.) This is usually accompanied by a reduction in CO2 emissions.

Remanufactured turbocharger parts

Turbocharger remanufacturing is very popular within the aftermarket as an original turbo part can often be very costly to replace.

A professional turbo remanufacturer will carry out a ‘pre-production’ inspection of all old units to ensure that only the best turbo core is selected for reman.

Once selected, the turbo is completely dismantled and individual components thoroughly cleaned to remove dirt or debris, prior to a shot blasting treatment that returns the parts to the same visual condition as new. All parts are then individually inspected to ensure they meet the original specification and tolerances.

Then the reman process begins. Crucial parts like bearings and seals are 100% renewed, and the core assembly, turbine shaft and wheel and compressor wheel are checked according to OE specifications. After all parts are prepared, the core assembly is balanced using a balancing machine and only when a unit passes the final balancing tests is it deemed ready for final assembly.

The future of remanufacturing

It’s not just the remanufacturing industry who is benefiting, vehicle manufacturers are also exploring how the extended service life of reman products can provide many benefits, as well as providing cost effective solutions for older vehicles.

An article in The Engineer magazine highlights that a long-time leader in the field of remanufacturing has been Caterpillar Inc, the world’s biggest manufacturer of construction and mining equipment and diesel engines. Since 1973 CAT has developed a sophisticated reman business model of salvaging materials, remaking parts and offering them with the same warranty as new parts. It is currently recovering 2.2 million products, or 63,000 tonnes, through its Reman programme for remanufacturing parts.

Truck manufacturer, Isuzu has also recently announced a truck engine reman programme to assist businesses and owner-drivers with Isuzu engine replacements. The reman engines are covered by a 12-month unlimited mileage warranty, as Isuzu state their reman engines provide a premium solution that is quality-assured, cost-effective and quickly returns vehicles to the road.

It’s not just commercial and heavy plant vehicles that are embracing remanufacturing. As Automotive World reports, a handful of OEMs, including Jaguar Land Rover, have been investigating the potential for reuse and reman.

“The circular economy covers a complex and wide range of initiatives ensuring we work to make the best use of the valuable resources that go into our vehicles. This includes technological innovation – such as recycling, remanufacturing, autonomous vehicles and ownership models that consider the future mobility needs of our customers,” suggested Adrian Tautscher, Sustainable Aluminium Strategies, Jaguar Land Rover.

Renault is a trailblazer for car manufacturers across the world. It generates around half a billion euros annually from the circular economy of recycling and remanufacturing and is investigating the expansion of its European reman model into other regions of the world, including India, Brazil, Morocco and China.

So, with benefits to the consumer, manufacturers and the wider world, it looks like remanufacturing will continue to exert an increasing influence on the automotive industry, whether for passenger or commercial vehicles. Work is still needed to eliminate remaining customer negativity but as has been shown with public acceptance of recycling, such attitudinal changes are certainly possible.