Whilst trying to determine where the annoying intermittent 'clonk' is coming from on the back of my Classic Wagon (Turbo 2000), I've noticed some very strange behaviour from my shock absorbers.

Firstly, I should mention that (as far as I'm aware), these are still the original shocks and springs - so 17 years old and 100K miles. General driving though, the suspension all feels good - nice and firm. I've had cars with worn shocks before, and this doesn't exhibit the bouncyness/wallowing or instability that I'd associate with worn shocks when driving.

But... I've found that if I leave the car for, say 5 mins, and then try and bounce the suspension, I get an initial large amount of bounce (and sometimes a 'clonk') - identical behavior to that which I would expect for worn shocks. However, after a couple of rebounds, it all stiffens up, and the suspension becomes nice and firm, seems to stay that way and all appears to be good. If I then leave the car again for a another 5 minutes, I get the initial 'weakness' again, which then promptly firms up again after a couple of rebounds.

I've tested the front suspension in the same primitive way, and it seems to do exactly the same thing - initially weak, and then firming up quickly.

Is this expected behaviour for standard Turbo 2000 shocks? I don't understand how they can go from 'weak' to 'strong' within a few bounces.

Has anyone got any suggestions or advice, or experienced this before?