Maintaining Your Diesel

Drive A Diesel? Here are some key things you need to know …

In our first blog, we look at some of the problems modern diesels experience and highlight how, by following a few simple rules, you can help prevent serious maintenance headaches.

Modern Diesel Engines Are Complex

There was a time when diesel engines were technologically simpler than their petrol equivalents. However, ever-tightening global exhaust emission and fuel efficiency regulations have resulted in diesel engines becoming more advanced, and in many cases far more complex than petrol engines. With this added complexity comes the potential for higher maintenance and repair costs.

Fortunately, the latest generation of diesel engines have been around long enough for the team at John Dale Motors to build up a huge knowledge base of best practice expertise to enable us to diagnose diesel problems quickly and accurately, fix them first time and importantly, advise our customers on how many of these problems can be avoided by following a few simple rules.

So let’s take a look at some of the problem areas …

Exhaust Gas Recirculation (EGR)

The exhaust gas recirculation valve, or EGR valve, recirculates exhaust gas back into the engine intake system for increased engine efficiency, reduced fuel consumption and lower NOx emissions.
The exhaust gas re-entering the intake system effectively changes the air entering the engine. This diluted mixture burns slower, lowering temperatures in the combustion chamber by almost 150°C, and reducing poisonous NOx production for cleaner, more efficient exhaust emissions.

EGR Valve Failure

EGR valves are subject to wear and tear over time. However, the single biggest cause of failure is the build-up of carbon particles from the exhaust gases in the EGR and intake system passages. Over time this will clog tubes, exhaust gas channels and eventually the valve’s plunger mechanism, causing it to either stick open or closed. Failures can also be caused by a rupture or leak in the valve diaphragm.

The symptoms associated with EGR valve failure include:

  • Check engine light: as with most engine management components, a problem with the EGR valve may trigger the check engine light.
  • Engine performance issues: if the valve is stuck open, the vehicle’s air-fuel ratio will be disrupted, causing engine performance issues such as reduced power, poor acceleration and rough idle. It may also produce turbo boost pressure leaks, causing the turbo to work harder.
  • Increased Exhaust Emissions. If the EGR valve is clogged or completely blocked, it can no longer re-burn harmful emissions inside the combustion chamber. The NOx emissions will flow unregulated through the combustion chamber and out of the exhaust pipe. The excessive NOx emissions will be seen as thick, black exhaust fumes.
  • Engine knock: higher temperatures and NOx may also result in increased detonation or knock, heard as knocking noises in the engine.
Blocked EGR

Diesel Particulate Filter (DPF)

A diesel particulate filter is a trap that captures and stores exhaust soot in order to reduce particulate emissions from diesel exhausts. Because they only have a limited capacity, this trapped soot must be periodically emptied or ‘burned off’ to clean the DPF and avoid blockage of the filter.

This regeneration process burns off the excess soot deposited in the filter, reducing the harmful black smoke you see from diesel vehicles, particularly when accelerating.

To make sure that the regeneration takes place, most manufacturers suggest that every few hundred kilometres, the vehicle is driven for a period of more than thirty minutes at a consistent speed in excess of 60 kph. Doing this will trigger a DPF regeneration to clean out the filter.

DPF Blockage

Short journeys at low speeds are the prime cause of blocked diesel particulate filters.

If blockage does occur, the DPF won’t be able to regenerate itself and will need to be cleaned or even replaced. Should the DPF need to be replaced, most manufacturers’ warranties will not cover the cost if the fault is deemed to have been caused by the owner’s driving style rather than a fault with the filter itself, potentially leaving you with a four-figure bill.

Poor Servicing

A DPF should last for around 200,000 kilometres, but on a poorly serviced vehicle may fail sooner. Check the recommended service intervals for your vehicle, and always make sure it is serviced on time.

It’s also important your workshop uses exactly the right type of oil – using the wrong oil can create by-products that block these filters.

Air Intake Carbon Build-Up

Carbon build-up on diesel engine components such as valves, fuel injectors and intake manifolds is a big problem. Carbon is like cholesterol, it slowly builds up over time, helping to block intake manifolds and restrict airflow through the inlet valves.

Causes include the use of poor-quality fuel, frequent short-distance trips, excessive idling, and infrequent oil changes.

This carbon build-up will slowly rob your engine of power and fuel economy. Tell-tale signs are check engine lights on, rough running and poor performance and fuel economy. Usually, when it gets to this stage, your vehicle is suffering from a heavy build-up of carbon in the induction system.

As always, preventative maintenance is the key, and we recommend regular cleaning of the intake and fuel system to ensure that carbon never builds up to the level where your vehicle will experience drivability issues or need expensive repairs.

Prevention Is Better Than Cure

There’s no point beating around the bush – fixing many of these problems on modern diesels can be expensive. For example, Diesel Particulate Filters alone can cost thousands of dollars, so we’ve compiled a list of things you can do to keep your diesel in tip-top health and prevent frustrating running problems and unexpected repair bills.

  1. Go for a long drive – frequent short distance driving is a killer for modern diesel engines, so make sure that at least once a month you get on the freeway or a dual carriageway and drive for at least forty-five minutes to clean out your DPF and help burn off carbon from your intake system.
  2. Always use quality fuel – premium quality fuel has a lower sulphur content, better lubricity and will clean the fuel system as you drive. As with everything in life, when it comes to fuel you get what you pay for, so buy the best.
  3. Service your vehicle on time – vehicles require servicing based on either distance or time. If your vehicle’s service schedule is every 15,000 kilometres or twelve months it’s important you get a service every twelve months, even if you have only driven five thousand kilometres since your last service.
  4. The correct oil is critical – diesel engine oils feature a higher-grade additive package than other oils. They also create less ash, which will keep your DPF cleaner for longer.
  5. Find a workshop with diesel expertise – as diesel vehicles have become more complex, many workshops have decided they are in the ‘too hard basket’ and have not kept up to date with modern diesel technology. This means that the very high levels of regular maintenance required by diesels are not always met, and when problems do occur, they do not have the expertise or tools to diagnose and fix the issue quickly and the first time.

At John Dale Motors, our team of experienced technicians are experts in the servicing of all makes and models of diesel vehicles, including passenger cars, four-wheel drives and commercial vehicles.

Our ongoing training ensures we stay ahead of the latest diesel engine technology and problem-solving techniques, to keep you on the road and unexpected repair bills at a minimum.

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The team at John Dale Motors are proud of our reputation for industry-leading technical excellence and outstanding customer service on the New South Wales Central Coast. We look forward to welcoming you.

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Delivering expert car servicing and repairs for most makes and models, combined with outstanding customer service to motorists in Charmhaven and throughout the Central Coast.


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(02) 4392 1327

4 Botham Close, Charmhaven 2263

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