The Audi S6, S7, and S8 were the first production vehicles to have the 4.0t V8 twin-turbo, abbreviated 4.0tt. The engine has a V8 configuration with a 90-degree angle, and it generates 520 horsepower and 479 lb-ft of torque at the crank. In addition to being standard on a wide range of Audis, Porsches, Bentleys, and Lamborghinis, it was also widely installed.
This cutting-edge motor used a novel cylinder on demand mechanism, which enabled the deactivation of four cylinders during light load operation. This technological advancement significantly decreased emissions while decreasing fuel usage by 5%. The Digital Trends 2018 Engine of the Year was the 4.0 TFSI v8.
All 2012–2018 Audis with the 4.0T engine 2012-2017 Audi C7 S6 Audi S7 2012-2018 The Current-Generation Audi D4 A8 2012-2020 Audi D5 A8. For the Years 2013-2019, the Audi D4 S8 2013-2018 Audi RS7 Aston Martin DB11, Audi C7 RS6, and BMW M3
Before delving into the typical issues with this engine, it’s important to note that it’s your responsibility to ensure that the new components really fit your car.
Problems with the Audi 4.0T Engine
- An Issue With The Ignition Coil
- Filtration Device for Turbo Oil Supply Line A Breakdown Caused by Clogged Motor Mounts
- Failure of the Positive Crankcase Ventilation Valve or the Engine Oil Separator
- Accidental Turning Down of the Heat
1: Broken Ignition Coil Pack or Spark Plugs
Many Audis have problems with their ignition coils and spark plugs. In order for the spark plugs to produce a spark and ignite the fuel, the voltage from the battery must be increased by the ignition coils. Normal wear and tear, or using an engine under less-than-ideal circumstances, seems to be the primary cause of failure for both of these.
If you follow this rule of thumb, you won’t have to worry about replacing your spark plugs until the 40,000-mile mark. When one of your ignition coils stops working, you should replace all 8. Even if it ends up costing a lot, it will have been money well spent.
The following are signs of a failing coil pack or spark plug:
- The Malfunction Indicator Lamp (MIL) Is On When the Engine Is Misfiring
- Idle roughness
- Poor Engine Performance No Start
Replacement Choices for the Coil Pack/Spark Plug:
It is recommended to change the spark plugs and ignition coils together to give the car a new set. If you have the right equipment, this is a very simple project you can do on your own. To avoid doing it yourself and instead have it fixed at a shop, you should expect to pay roughly $1,200. This is mostly due to the price of the necessary components.
- Replacement Ignition Coil Pack for 4.0T Vehicles Available Here
- Get Your Spark Plugs for Your 4.0T Here!
2. Clogged Filter in Audi 4.0T Turbo Oil Supply Line
Many blown turbochargers may be traced back to this issue, which is widespread in Audi 4.0tts. There are a number of different names for this component, but its primary function is to filter oil before it enters the turbocharger to prevent dirty oil from damaging the turbos. Insufficient oil was reaching the turbos, and the filters were failing straight from the factory.
Due to its prevalence, Audi released TSB 21 18 30 2044640/5 to fix the filter. Audi has released a number of modifications to the filter in response to customer feedback about the problems it was creating. Make sure the engine in any Audi 4.0ts you own or are considering buying have been changed.
Turbo Oil Filter Clogging, Symptoms of Advanced Age:
- Overheated turbochargers
- Breakdown of the engine
- Rough running engine
- Sluggish engine performance
- An inadequate amount of oil pressure
Replacement Filters for Turbo Oil Supply Lines:
Get a new set of filters for the turbo oil supply on any Audi 4.0tt you’re thinking of buying or already possess. The filters in this project are not the simplest to access, but if you are familiar with the engine, you should be able to change them out on your own. A trip to the repair shop would set you back about $750, most of which would go toward paying the mechanics.
DIY Project: Intermediate in Difficulty
3. Failed Active Motor Mounts in an Audi 4.0T
Active motor mount failure was another prevalent issue with 4.0t engines. Upon its first release, the Audi 4.0t featured cutting-edge technology in the form of active motor mounts. Active mounts are designed to minimize road noise and vibrations caused by the engine.
Due to the widespread nature of this issue, Audi issued TSB 27 14 22 2036392/2 to rectify it in all 4.0t engines. These may break for two reasons: either the mounts were defective from the outset or they have worn out over time. Also, if you already own or are considering buying a 4.0t, double-check that it has the most recent updates that Audi has issued.
Active Motor Mount Failure Indicators:
- Vibrations from the engine, heavy
- Various pounding, clanking, and other impact sounds emanating from an engine.
- Motion of the Engine
Options for Alternate Active Motor Mounting:
When an active motor mount fails, you may either get a brand new original equipment manufacturer replacement or a used aftermarket one. The aftermarket component is not only superior to the OEM component in price, but also in many other respects. Even if it’s not the simplest do-it-yourself project, you can do it in a day. The cost of having this service performed in a store may exceed $1,000.
Shop Here for a New OEM Active Motor Mount for Your 4.0T
DIY Project: Intermediate in Difficulty
3. Engine Oil Separator/PCV Valve Failure
The PCV valve or engine oil separator on an Audi or Volkswagen is notoriously unreliable right out of the factory. Before the oil enters the combustion chamber, they purge it of any lingering gases. If they break, the engine’s air-fuel ratio (AFR) will be wrong, leading to the following problems.
A checkup of this component is needed every 60,000 miles since it will inevitably break down once throughout the life of the vehicle. Normal wear and tear, or being trapped open or closed, are the two major causes of this component failing.
Signs of a Faulty PCV Valve or Engine Oil Separator
- Engine misfires at low RPMs
- The engine is making a whistling sound.
- Acute Food Scarcity (AFR)
Options for Changing the PCV Valve/Engine Oil Separator:
If the engine oil separator fails, the best solution is to get a new one. DIY replacement is easy and the cost of the component is little. About $600 total, including parts and labor, will be needed to have this fixed at a repair facility.
You Can Get a New PCV Valve and Oil Separator for Your 4.0T Here
Do-It-Yourself Ease Scale: Low
4. Thermostat Failure
Another widespread issue with Volkswagen and Audi engines is broken thermostats. A vehicle’s cooling system is not complete without a thermostat. To control how much coolant is cooled in the radiator before being recirculated to the engine, this valve is installed. If the thermostat fails, the engine will overheat quickly and you won’t be able to drive for very long.
Apparently this was a widespread issue with 4.0t’s, since Audi TSB 19J1 was released to fix the thermostat. Do not delay in replacing the thermostat if it has not already been done so in accordance with the TSB mentioned above. Up to 70,000 miles is the typical lifespan of a thermostat in regular use.
Failure of the Thermostat to Show Symptoms
- Overheated engine
- Poor amounts of cooling liquid
- Lack of consistency in engine temperature
- Complaining squeal from the powertrain
When a 4.0tt’s thermostat fails, it’s advisable to replace the whole device rather than try to repair it. Again, similar to the engine oil separator, you may save money and time by building one yourself since the components are inexpensive. Taking it to a repair shop to get it replaced will set you back around $800.
Replace Your 4.0T Thermostat here.
Reliability of the Audi 4.0t
The turbo oil supply line filter often becomes clogged, resulting in blown turbos, and hence a negative reputation for the Audi 4.0t engine’s dependability. If regular maintenance is performed, the Audi 4.0t engine has a failure rate of less than 5% and is quite reliable otherwise. It’s important to note that, as could be anticipated, this engine’s upkeep and fixes are not inexpensive. Unless we want to spend a lot of money on maintenance, we don’t see this engine lasting much further than 120,000 miles.
Dmitry Petrov is an engineer who specializes in materials science, and has a deep passion for all things related to automotive technology. He is a true motorhead at heart, and spends much of his free time tinkering with engines and studying vehicular dynamics.