Disclaimer: Please note all information provided is intended for basic knowledge of the vehicle & parts. Suncore Industries is not liable for any damage incurred during any attempt to follow the information shown in the video above.

Troubleshooting: What Part of The C5 Suspension is Failing?

The Audi Allroad Quattro is a dynamic car with the space and cargo of a station wagon but the off roading capabilities that have been compared to the Jeep. While the 2001-2005 Audi C5 is still sought after for its diverse performance features, a common issue with the Allroad C5 is the body dropping and refusing to maintain ride height adjustment features or lift into Jack Mode. When you see signs of failing suspension, the first thing you must do is find the source of the problem.

The Allroad C5 uses an Adaptive Air Suspension system with height sensors in all four corners. You will have electrical components to inspect as well as air supply systems to consider when working on the C5’s suspension. To make these complex systems a little easier, these are some of the basic guidelines to the common issues found in this type of air suspension system.

  1. Listen to the air compressor. If it whines, grinds, or clicks the chances are the motor or fan has gone bad and will need to be replaced. Once replaced you can troubleshoot the air springs and struts to make sure they are holding air pressure.

  2. If the compressor doesn’t run at all you will have to check for a blown fuse and bad electrical connections. Replace wires that look distressed and make sure connectors have solid contact. This would also be a good time to check level sensors to make sure they haven’t been bent which will provide the suspension with false readings. If the electrical components all come back as okay and the compressor still isn’t running, it’s time to replace it.

  3. If the air compressor is running fine, your next area of troubleshooting is the air lines and bellows. You can use soapy water in a spray bottle to follow the air lines from the compressor to the wheel well, including the front air struts and rear air spring bellows. Bubbles will form wherever there is a leak and you will know which part needs to be replaced.

TIP: If one air strut is leaking and not the other, you will want to replace them in pairs. They wear down together and when one leaks the other is right behind it. This will also help you keep track of when you repaired portions of your suspension and will help take the pressure off your air compressor.

If you are finding several air leaks, replacing air lines and springs or struts in all corners of the vehicle will maintain a steady level of air pressure throughout the entire suspension system.

Replacing Front Air Struts

Because the Allroad C5 has such a dynamic air suspension system, a common issue is the air struts losing air overnight which makes one side or the other have a noticeable height difference. If the front end is experiencing the problem then the 4-level air suspension won’t be able to keep up and the rear will rise while the front points downwards, risking nose dives. Replacing the front struts will help your Allroad C5 lift faster when changing air levels and will improve your steer handling for better ride control.

The Allroad C5 is considered relatively easy to work on, and this video gives you step by step instructions on how to take out your old front air struts and how to install replacements. The list below is some tips to keep in mind as well as the tools you’ll need to follow the installation video.

What To Keep In Mind When Replacing Front Air Struts on Your C5

  • Be sure to watch the level sensor wire located on the control arm in each corner. Damage to this wire will cause the air suspension to fail and warning lights to appear on the dash.

  • When removing the air connection, the collet may damage the end of the air line. To ensure proper fit of the collet you may need to snip the end of the line or carefully use a screwdriver to open the collet enough to fit the entire tube opening into the connector.

  • When assembling the new air strut into the top hat, align the groove at the center front of the top hat with the forward-facing mounting hole for correct positioning as shown to the right:

  • Replacing Rear Air Struts

    Like the front suspension, when the rear struts fail to remain inflated the back end will drop. Not only does this cause the back end to scrape and bottom out, but the Allroad C5 loses its independent self-leveling feature resulting in horribly bumpy rides and an inability to do any light loading or towing, which is exactly what the C5 was built for.

    To get your rear end back up to its original ride height and load leveling capacity you’ll need to change out your rear air struts. This video will guide you through the process to make rear strut replacement easy for you. Remember to be gentle with the collets on the air lines and the level sensors on the control arms. Here are some additional tips on the rear air struts and the tools you will need to prepare your work space.

    Audi C5 Rear Air Strut Replacement Tips

  • Spray your pinch bolts with rust penetrating oil the night before replacing the rear air strut so it comes off easily.

  • The lower strut mount bolt will have its head facing the rear of the car if they have not been touched since factory assembly. This will require a floor jack to position the lower control arms so the bolt can be removed.

  • During re-installation be sure to listen for air leaks before putting the wheels back on.

  • Replacing the Air Compressor

    If the air compressor is overworked from age or faulty spring assemblies, or doesn’t run at all, you will need to replace it to maintain the Allroad C5’s air suspension.

    Before jumping into the air compressor installation at home, watch this step by step installation video. If you need to buy a new compressor be sure to find a direct replacement part that includes a relay. Without the relay you will not be able to utilize the Jack Lift Mode and you will not be able to drop your suspension when you need more grip on the road. A great replacement part is Suncore’s C5 Air Ride Suspension Air Compressor with Dryer for the Audi Allroad Quattro, the parts are linked at the bottom of this page for reference.

    Torque Specs

    Front Strut Torque Specs
    Top Mount to Chassis 23 Nm
    Mount to Strut 40Nm
    Control Arm To Mount 50Nm
    Lower Mounting Bolt 90Nm
    Turn an Additional 90° After First Click