Not a week passes where we are not asked by a consumer or repair garage to recommend a solution for clogged turbo chargers, particularly variable vane equipped units on diesel engines.
While turbo chargers offer enhanced performance for both petrol and diesel vehicles, they’re not without their problems. One of those is maintenance and cleaning – carbon can build up over time and use, threatening the operation of the turbo, as well as other post-combustion components in the engine.
Understanding the Situation:
Let’s address why turbo chargers clog up or accumulate deposits. A turbo is essentially driven by exhaust gases. These gases are the result of the combustion process and contain particulates, hydrocarbons and even oil that have entered the system. What happens is that these particulates build up on the hot side of the turbo. The carbon can also build up on the waste gate, which creates problems for the turbo actuator in controlling boost. The waste gate can then stick, which means the solenoid that controls the actuator is affected because it’s trying to draw more current than it’s designed for. The ECU picks up this condition and throws a warning light, putting the vehicle in limp mode.
With diesel engines, the most common issue is the accumulation of carbon on the variable vanes mechanism resulting in sticking or complete seizure. This creates either an under-boost or over-boost condition usually resulting in an engine warning light and tripping the limp home mode, restricting the vehicle to low power and 2.5k to 3k RPM.
Why do turbo chargers accumulate deposits in the first place?
1. Accumulated deposits in the fuel system and combustion area will result in a lower quality of combustion resulting in additional hydrocarbons that will deposit in the post combustion areas such as the turbo charger.
2. Driving styles and type of journeys. Stop start driving and/or short trips will take its toll as the engine is unable to reach sufficient temperature to optimise the quality of combustion and/or help burn off existing carbon deposits. More hydrocarbons are produced whilst the engine is in its warm up cycle.
3. Oil – this is the missing link. Many believe that post combustion carbonaceous deposits are the result of uncombusted fuel only. This is not true. On diesel vehicles especially, the carbon is a mix of fuel AND oil. Oil bypassing the piston rings will end up in the combustion chamber, will not be fully combusted and will end up being deposited in the post combustion areas such as the turbo, DPF, EGR etc. Oil recirculating from the crankcase breather system can also deposit within the intake system.
From the above you can see that there are a number of contributory factors.
Turbo Carbon Removal:
If you are unfortunate enough to have a turbo diagnosed with excessive carbon build-up then there are a number of options available to you. Firstly, politely decline any suggestion that the turbo must be replaced unless the unit is proven to be faulty, damaged or excessively worn. Excessive carbon does not fall into any of these categories.
It is equally important to address the cause as well as any remedial work or treatments. It’s pointless tackling the carbon on the turbo directly without ensuring the fuel system is running efficiently, because the chances are high that the turbo will just accumulate more carbon immediately after cleaning if the fuel system isn’t clean and operating properly. I hear time and time again of garages replacing turbos only for the same problem to reoccur shortly after with the newly replaced unit. This may be profitable for the garage but not very cost effective or convenient for the customer.
Therefore, when looking to resolve this issue, the first thing you need to do is make sure the fuel system is clean and operating correctly. There are a variety of products on the market that will achieve this.
In tank fuel cleaners:
Forget the cheap cleaners as these rely on the principle of natural cleaning through carbon scavenging. If you want to learn a bit more about that, read our article “EGR cleaning and EGR Cleaners”. What these products do is clean the fuel system and improve the quality of the combustion process, which result in cleaner exhaust gases. These cleaner exhaust gases, combined with heat, can naturally scavenge and clean the carbon from all post-combustion areas, including the turbo. This is somewhat effective but you achieve the same results from a high quality fuel system cleaner.
If a fuel system cleaner doesn’t fully resolve the problem then you could try a dedicated turbo cleaner. Again, there are many products available but most share a common flaw – they are post combustion fuel catalysts that only address post combustion carbon leaving the fuel system alone.
The best solution is a chemistry that combines modern high-strength detergents to ensure the fuel system is clean AND fuel borne catalyst technology to remove and burn off post combustion carbons.
For this we recommend the Archoil AR6400-D MAX as it uses various detergents and fuel borne catalyst technology that survives the combustion process and is still active post combustion to provide the best chance of removing deposits. If AR6400-D doesn’t work then no other fuel based turbo cleaner will make a difference.
This type of approach works 8/10 times, which is the highest success rate we have seen by far. Also remember that heat is your friend and occasionally dropping a gear or two to increase temperatures will assist the cleaning process.
If unsuccessful, then the only other option (other than cleaning the turbo in situ or removing it) is to try an aerosol based cleaner than is sprayed into the air intake. The good ones contain a blend of chemicals, some of which survive the combustion process and reach the turbo. They are best used when the engine is cold as more product will reach the turbo.
Only those turbos that are severely seized with a combination of solidified fuel and oil-based carbonaceous deposits may not respond to these treatments. If unsuccessful then the only solution is the remove the turbo for manual cleaning.
Remove turbo for cleaning:
As a last resort the turbo will need to be removed and professionally cleaned using the correct detergents.
Prevention and Maintenance:
Carrying out the below will provide the best possible chance of preventing deposit build-up and potential malfunction of the turbo charger.
1. Keep the fuel system and combustion area running efficiently by using a high quality fuel system cleaner and carbon remover such as Archoil AR6400-D and follow up regularly with Oilem Hybrogen Road or AR6900-D MAX. This will improve the quality of combustion and reduce the amount of recirculating hydrocarbons, even when the engine is cold!
2. Use the best quality oil possible or at the very least fortify it with an additive such as Archoil AR9100, AR9200 or AR9400. Not only will this protect the turbo against wear but it will keep the crankcase clean, maintain engine compression (this reduces oil bypassing the piston rings) and help prevent adhesion within the intake system, turbo and EGR even if it does bypass the rings or crankcase breather system.
3. If you suspect a reduction of cylinder compression then use a professional engine flush or advanced cleaner such as Archoil AR2300, followed by an oil change. It is often postulated that compression loss is the result of engine (piston/rings/cylinder) wear. This is not always the case. Most compression loss conditions are actually the result of deposit build-up on the piston rings and/or skirts. The build-up then forces the rings from the bore and thus reduces engine compression. A professional flush will resolve this quickly and effectively. A high quality oil and/or additive pack such as AR9100, AR9200 or AR9400 will then prevent any future deposit build-up or compression loss.
4. Occasionally drop down a gear or two to increase the revs and thus increase the temperature. Heat is your best friend when it comes to removing carbon. This is also important when using any fuel additives as it will enhance the efficacy of the cleaning chemistry.
Many oils, particularly expensive fully synthetic oils that have low SAP or low ash content designed for DPF-equipped vehicles, do not have sufficient quality or enough additive strength to keep the turbo well lubricated for the extended oil drain cycles that we now see. Some are supposedly designed to last up to and beyond 20,000 miles. However, from our experience and oil analysis, we are finding that these oils begin to struggle long before that mileage is reached.
I would recommend researching your engine and vehicle to understand the susceptibility of the turbo charger to failure or deposit accumulation. If there are documented cases of either of these, we advise that you use the appropriate lubricants and additives to ensure your vehicle does not encounter the same problems. If you need any further advice on this matter then please don’t hesitate to contact us.
Summary of Product Links:
High strength Fuel System, Turbo Cleaner & Carbon Remover
Pro Fuel Conditioner to Keep System Clean & Lower Hydrocarbon Build-up
Hybrogen or AR6900-D MAX
Oil Additive to reduce oil-based carbon build-up
Please note that we no longer support the use of the Bardahl Turbo Cleaner