They could be the pressure type [I had them on my Vauxhall Astra Estate] which has a valve usually situated behind the side panels. Heavy load! then the shocks were pumped up to accomdate the heavy load and prevent the springs from 'bottoming' by pumping up by garage and making the suspension harder. You released the pressure to soft ride when heavy loads completed.
Of course they could be standard type and one that side has leaked all its pressure/oil
I changed mine to the standard shockabsorbers because the pressure vary ones are very expensive or they were back in the 80's.
Rob
June 2008