I replaced my accumulators about a month ago. What a difference. Car rides great, but most significantly, it doesn't drop down overnight. I had thought that the overnight drooping was caused by a bad control valve but apparently not. It was bad accumulators.
But here's my question: I've noticed that when a load is removed from the car, with the engine off, I can hear a hiss as the control valve releases pressure to bring the rear end down to the correct height. I first noticed it when I removed my 200lb raft from the back compartment. But I can hear if even if a couple of passengers get out of the car. Is this normal? I can't recall ever hearing it before I replaced the accumulators.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13