sagging rear suspension - air spring or shock absorber failure

[nooreaga]

context - 2014 C7 RS6 with Air Suspension
My rear suspension has been acting weird. Sometimes after the car has been parked and off for a while I will come back to find the rear suspension sagging significantly (low enough that the rear tires tucks into the fender.

but, as soon as I unlock the doors I can hear the air hissing and the suspensions raises back to the standard height. This does not happen all the time. Sometime i happens when the car has been parked for an hour, and doesn't when the car is parked overnight or for the weekend.

I had a mechanic Shop take a look and they said my rear shock absorbers need to be replaced. How can I tell if it's the air springs or the shock absorbers that are the culprits?

My assumption is that shock absorber is the problem and is not "carrying its weight" and the air spring is covering for it when the car is on and compressor is pumping air. When the car turns off though is it normal for the air spring to "deflate"

[alex760]

I had an old 5 series with this exact problem, fairly common in those circles to happen. Obviously not same but in principle it is. I changed the compressor and the solenoid block and it cured it. Problem is something is intermittently leaking and allowing air to escape from the rear air springs, when you start the car the compressor kicks in and pumps them back up.

The damper doesn't affect the height at which the car sits, the air spring does. If you imagine a traditional spring setup you can have a completely blown damper and the ride will be terrible but the resting height will be the same. It is the same for an air spring.

[nooreaga]

I had an old 5 series with this exact problem, fairly common in those circles to happen. Obviously not same but in principle it is. I changed the compressor and the solenoid block and it cured it. Problem is something is intermittently leaking and allowing air to escape from the rear air springs, when you start the car the compressor kicks in and pumps them back up.

The damper doesn't affect the height at which the car sits, the air spring does. If you imagine a traditional spring setup you can have a completely blown damper and the ride will be terrible but the resting height will be the same. It is the same for an air spring.

Thank you! This is the reason I posted. It didn't make sense that the shock absorbers were the issue. Granted, they may still need to be replaced - but I did not think they were the cause of the sagging.