This bulletin applies to 2008 Audi Carbriolet A4, S4 and RS4 vehicles with noisy power steering.
If the power steering fluid is below the minimum mark during cold conditions, air may be drawn into the power steering pump. If system components were replaced or disconnected, system filling or bleeding procedures may not have been carried out properly.
Do not replace any power steering system components until the following is checked:
1. Verify the customer concern.
2. Check the power steering fluid level.
3. Check the system for leaks.
4. Check installation of the filter/screen in the reservoir.
5. Check for other possible sources of noise such as belt driven engine accessories (belts and brackets).
6. Ensure that hoses are not rubbing against the body or other components.
7. Ensure that the suction line from the reservoir to the pump is not squeezed, pinched or twisted, causing reduced fluid flow.
8. Check the fluid level.
With engine cold (outside temperature approximately 68 degrees Fahrenheit), fluid level must be at the MAX level. With the engine warm (engine oil temperature 176 degrees F), fluid level must be 10 mm above the MAX level.
9. If the fluid level is below the MIN mark (engine hot or cold), there is a chance that air has entered the system.
a.Test drive the vehicle to warm up the fluid.
b. Park the vehicle. Switch the ignition off and let the vehicle sit for one minute.
c. After one minute, open the fluid reservoir and inspect for air bubbles. If air bubbles are not present, no air is in the system. Air is not causing the noise. Check other system components.
d. Allow the vehicle to sit for at least two hours.
e. Check fluid level and add as necessary.
f. Perform a test drive to ensure that the noise has been eliminated.
g. It may be necessary to repeat this process more than once.
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