More than 20 years ago, Audi introduced the A4, a brand-new model that completely revitalized the brand and firmly established the Volkswagen Group as one of the leaders in cutting-edge automotive engineering. While the A4 was new to the Audi line-up, it continued the lineage of the venerable Audi 80 and was built upon a new edition of the same Volkswagen Group B platform, now designated the B5.
The Audi A4 had the distinction of being the first vehicle from the Volkswagen Group to be powered by the now legendary 1.8 liter 20 valve turbocharged engine which has gone on to be used in nearly every model line from each of Volkswagen’s major brands. If you think about it, there probably isn’t a day that goes by where you don’t see a car powered by one of these engines. In fact, Volkswagen is still producing it to this day while it continues to provide motive power in all of their brands as well as their industrial offerings. There’s even a version that is used in the FIA Formula Two Championship capable of 450hp!
One of the great things about turbocharging is that it allows the relatively small engine to produce much more power than similarly-sized engines that are naturally aspirated. Under load or heavy acceleration, the turbo will scavenge waste energy from heavy exhaust gasses exiting the engine and use it to compress intake air into a smaller and denser volume. By getting more air, and therefore more fuel, into the combustion chamber, a turbocharger can in essence dynamically increase the displacement and power of the engine. With a different fueling profile, the same mechanism can be used to recycle some energy back into the intake, letting the engine breathe easier and improving overall fuel economy. In the mid-nineties this combination of power and efficiency blew away the competition with almost 170hp and 28 mpg on the highway, numbers that are still pretty good today.
However, it didn’t take long after introduction for the problems to start creeping up. In most cases, the problems had to do with oil sludge and varnish deposits left in the engine. If the owner wasn’t meticulous about changing their oil (and let’s face it, most of us aren’t) these deposits could build up and obstruct oil passages, leading to premature engine wear and even failure if the rotating surfaces were starved of oil for long enough.
Eventually, the problems were traced to engine oil pooling and breaking down inside the hot turbo after the car was driven. A service bulletin was issued and Audi began requiring fully synthetic motor oil along with a larger oil filter from the optional V6 engine to increase total oil capacity. For a long time these measures worked and the 1.8t engine was mostly free from serious problems. Over time, it even developed a reputation as a reliable and efficient powerplant.
But with many of the first Audi A4s now hitting the 200,000 mile mark, even the best maintained 1.8t engines are starting to show their age and some may be in need of a replacement turbocharger. While it is easy to diagnose needed maintenance and many issues with engine belts, hoses, fluids, or filters, wear or failure of the Audi turbocharger is often invisible to the untrained eye.
If you suspect that the turbocharger in your Audi has failed there are a few things you should keep an eye out for. One of the most common problems that can lead to turbocharger failure is turbine shaft bearing wear. These bearings not only hold the turbine in place while it spins at up to 250,000 rpm, they also maintain the seal that keeps oil and coolant inside the center housing. Often, when these bearings fail they’ll develop excessive play that will cause the turbine shaft to rattle at certain engine speeds, or let oil and coolant seep out through the exhaust where it will be visible as smoke coming from your exhaust.
Another place where there can be problems is at the compressor wheel. Occasionally, small pieces of debris can get past the filter and into the intake where they can strike and damage the leading edges of the compressor wheel fins while the turbo is spinning. This can throw off the delicate balance of the turbo rotating assembly causing further wear and loss of boost pressure. Often damage to the compressor wheel isn’t diagnosable without first removing the turbo inlet piping and examining the wheel visually.
There can even be problems with the integrated wastegate. The wastegate is a valve that allows some exhaust gasses to bypass the turbine. On the Audi A4, it’s controlled by a vacuum actuator through a short linkage. This allows the valve to open at higher engine speeds in order to control excessive boost pressure. It is also attached directly to the side of the turbocharger which is one of the harshest environments under the hood of your Audi where the ambient temperature can reach hundreds of degrees. Problems with the wastegate will occur in one of three places: the valve in the exhaust-side of the turbine housing, within the linkage, or in the vacuum actuator. A problem with any of these components will let exhaust gasses out prematurely, limiting the turbochargers ability to produce boost. And because the wastegate is integrated into the housing of the Audi A4’s turbo, it often necessitates the costly replacement of the entire turbocharger assembly.
Fortunately, BuyAutoParts.com has you covered with replacement Audi A4 turbochargers that will save you from breaking the bank on a new unit. We stock the highest quality OE replacement units, as well as genuine BorgWarnerStigan turbos. We even carry high performance K04 versions that will transform your humble 4-door into a road-devouring sport sedan! If you suspect your Audi A4 is in need of a replacement turbocharger, get in contact with one of our helpful parts experts who’ll help make sure you get the right parts that are a guaranteed exact fit for your vehicle.
Ready to purchase your Turbocharger? Check out our Turbocharger buying guide to help make a well informed purchase decision. If you would like to speak with a BuyAutoParts.com specialist about turbos, please call (888) 907-7225. When it comes to quality car parts, we are proud to be your preferred project partner