How do you test for balljoints on a 300SE??

[dracman]

I've got a '91 300SE that runs really well but has developed a 'clunk' sound in the left front suspension over the past month. On the highway it sounds and runs just fine but get on a bumpy road and it'll make you cringe.
I've jacked up the front and tried to wiggle the tires.... all seems really tight. I've been told that you can't test balljoints on the SE this way. Can anyone help me with this problem.
I'm only assuming it's balljoints because I can't find anything else that's loose or could make that sound.

Thanks!