Audi 2.7T Common Problems Here

This section is intended to expose many of the more common problems with the B5 S4.

The electronic ABS module commonly fails on these cars and it is very apparent when it does. Upon starting the car, the ABS and the BRAKE indicators on the gauge cluster should illuminate, generating several high pitched beeps. The lights will remain lit until the unit is replaced / repaired and the codes are cleared from the ECU.

Sometimes these indications can be caused by a sensor failure, however the module itself may be the cause of the issue. A replacement module is very expensive, so check your codes to be sure you don't simply have to replace the sensor.

There are companies that will rebuild failed modules at a fraction of the cost of a brand new module.

The gauge cluster very commonly fails in small stripe patterns or 'pixel errors' both horizontally and vertically. Essentially, a string of 'dead pixels' will appear on the digital screen making it difficult to read the notifications displayed. these dead pixels could appear temporarily, but typically will reappear in time. This is most often effected by changes in temperature. There is no easy fix for this and usually requires replacing the cluster altogether which can be expensive.

There are companies, however, that repair pixel errors in gauge cluster for less than what a new cluster would cost. One example of this type of service is http://www.tachopix.de/

Clearly this is a big problem, as the repair will run you >$6000 if you are not under warranty, but it is usually attributable to one of a few weak points in the system (listed below). These trouble spots can create big problems for your turbo if malfunctioning. If you're interested in buying an S4, it's usually good if the seller at least has a knowledge of the potential problems, and even better if they have been remedied. Turbo failure rate does increase when performance modifications are made to the car. Naturally when you demand more activity of your turbo (to give you more power) it's going to see more wear, and probably premature failure.

The following video demonstrates the sound a dead turbo makes:

The Throttle Body Boot - A small rubber boot that connects the two pipes that deliver air from the intercoolers to the throttle body. It is shaped like a truncated “Y”, and frequently tears due to overtight clamps or simply a defective design (poor material). Several fixes are available on the aftermarket: Samco makes a silicon TBB, and it's available for about $60 when I checked last. Some individuals have complained that it does not fit quite properly, and you usually need to buy clamps separately, but it is usually a serviceable part. Another alternative is AMS' Kevlar-wrapped TBB. This is merely a stock TBB with a layer of Kevlar wrapped around it. I cannot recall seeing a failed one listed on the forum, and it looks and fits identically to the stock TBB. This is available for about $90. What most regard as the best replacement for the TBB, however, is a part called the Bipipe. Made by APR, it is a “Y” shaped pipe made of metal that replaces the TBB and the metal intercooler pipes feeding it. It runs about $350 from APR, and is generally regarded as a foolproof fix to the problem. Other options are available, but they will not be addressed here. Here is an AW tech article on TBB replacement: http://www.audiworld.com/tech/eng19.shtml

The following Video demonstrates the 'Dentis Drill' sound that can be caused by a torn throttle body boot.

Instead of using Blow Off Valves, like many turbo cars, the S4 uses Diverter Valves, or bypass valves. There are two DVs (one for each turbo) that frequently fail because of a poor design by the manufacturer. Note that the DVs have an exceptionally high probability of failure if the vehicle is modified to increase performance, but even without modifications, they frequently break.

The most common solution is to replace each one with the DVs found in the Audi TT 225 (called 710Ns, by part #), which are a more robust design. Each will run you no more than $35, and can be replaced easily by yourself using the tech write-up on AW. These DVs are known to perform well even with significant performance modification to the vehicle. Other DV options exist through aftermarket manufacturers such as Bailey, Forge, Stratmosphere, and many more. More information about the B5 and Diverter Valves can be found here. The difference between these valves and the TT valves is that they are constructed of metal. They are considered very robust, but require internal lubrication from time to time. These typically run anywhere from $200-$350 for the pair. Here is an AudiWorld tech article on DVs: http://www.audiworld.com/tech/eng21.shtml

This problem is exclusive to the 2000 and early 2001 model years (late 2001 year models had numerous changes, and are typically referred to as 2001.5). In the S4s where this is an issue, the F-hose is a little hose that, oddly enough, is shaped like an “F”, and is made of rubber. It is prone to tearing. Alternatives available are one made by MTM, which is a metal pipe fashioned in the required shape with rubber connections; cost is about $80. Samco makes a silicon F hose that runs closer to $25. Both seem to work just fine. Note that the F-hose doesn't seem to be as common of a problem as the aforementioned parts.

Some seats like to “rock” back and forth as if there is play in the track. This problem was usually fixed under warranty. If not you can see the following Audiworld thread for the fix:

• Rocking Seat Fix Thread

In earlier models, the pump housing will commonly split as a result of a defect. The design has since been changed.

It is very common to have the secondary water pump which is located under the intake manifold crack and leak. This will cause a constant loss of coolant and if the problem gets bad enough you will be in danger of overheating or damaging other components due to extreme heat. The replacement pump is relatively inexpensive, however the repair time is as much as 4 hours making this a moderately expensive repair unless you are doing it yourself.

This AW thread explains the phenomenon: http://forums.audiworld.com/s4/msgs/691866.phtml. Coupled with weak synchros and a user-base that is frequently running significantly higher-than-stock performance powerplants, this problem *can* cause premature transmission failure. Typically if you treat your gearbox nicely, it will not have problems, so don't power shift through the gears and you should be okay. Transmission problems can also be caused by improper installation of a short-throw shift kit. Follow directions closely if installing one. Just pray that your transmission problems crop up while you are under warranty (if at all), because they will be a VERY expensive fix if you aren't. Do not become overly worried about this issue, many S4s have had no transmission issues at all (like mine).

The mass air flow sensor detects the rate at which air is entering your intake system (to go to the engine). They frequently fail due to (you guessed it) poor design, and could cause gas mileage problems, or a rich or lean condition, even a loss of power. This is about a $350 part (and really easy to replace), so it's not crazy expensive if it goes, but just be aware. This problem appears to be generally limited to MY 2000 cars.

This problem is (some say) due to the end caps on the IC tanks being made of plastic versus the metal of the IC. When they leak, you'll get a loss of power due to the pressurized air that's escaping. Not a terribly common problem.

Due to their very large size (swept area) and inability to trasnmit heat to their surroundings efficiently, uneven brake pad deposits are frequently left on the rotors. This can result in poor braking performance, and can cause a sort of shuddering experience during hard braking. Many people simply buy inexpensive (in some cases cheaper than replacement OEM) aftermarket rotors which perform well with stock calipers. A set of aftermarket front rotors (good ones) can cost you as little as about $200.

Fan internal to the climate control unit makes a buzzing noise. Replacing the fan fixes the problem.

Often the fuel level sending unit will fail. This is a relatively inexpensive repair in comparison to most other common problems with the B5 S4. This unit sits inside the gas tank, measures the fuel level in the tank and reports it. http://www.audiforums.com/m_20295/tm.htm