One air strut has failed. Do I have to do all four?
No. Same axle together is the sensible rule, the way it is with any damper, because two different rates across an axle change how the car behaves under braking. All four at once is a decision about age, not a technical requirement: if the other struts are the same age and have lived through the same summers they are on the same clock, and we will say so — but we will not present that as the only option.
Can I convert the air suspension to normal springs?
Conversion kits exist and people fit them. What you should know before you decide: the suspension module still expects ride-height signals and will normally log faults and light the dash unless that is dealt with, the ride is not the one the car was engineered around, and on models where the rear self-levels the loaded behaviour changes. We will tell you what it will actually do on your specific model before you spend anything, including where it is the wrong idea.
My compressor was replaced last year and it has failed again. Why?
Almost always because the leak that killed the first one was never found. The compressor is a small pump with a duty cycle; a strut or a valve block bleeding air makes it run until it overheats, and it dies of overwork rather than of age. That is why the leak test comes before the compressor quote here, and why we would rather tell you the job is bigger than you hoped than sell you the same part twice.
Is the 7G-Tronic gearbox really filled for life?
Mercedes-Benz publishes fluid and filter intervals for these gearboxes. "Sealed for life" is a phrase that travelled through the trade, not a manufacturer instruction, and a gearbox in this country lives at a fluid temperature Europe rarely sees. The important part is how it is refilled: the 722.9 has no dipstick, so the level is set with the fluid at a stated temperature and read electronically. Done any other way the level is wrong even if the right amount went in.
Why do several unrelated warnings appear on my Mercedes at once?
Because a dozen modules share one supply, and on these cars a weak battery shows itself as a list of faults rather than as a slow crank. Heat is what ends a battery here, not cold. There are two more items worth naming: the auxiliary battery — on some models a small capacitor-based voltage converter rather than a battery — which throws its own message, and a parasitic drain from a module that never goes to sleep. On the W211 the rear SAM sits where water from a blocked plenum drain reaches it, and a wet SAM produces faults that look like anything except water. We measure the drain and load-test the battery before replacing modules.
Do you work on the diesel models?
Yes, but honestly: diesel passenger Mercedes are far less common on the road here than in Europe, and most of what arrives is an OM642 V6 in an older ML, GL or a van. We would rather tell you that than copy out a European diesel fault list as if it were the local picture. If you have one, bring it and we will look at it on its own terms — and if a part or a job on it has to come through a channel we cannot reach quickly, you will hear that before the car is stripped, not after.
