bumping

I've a 2000 W208 CLK and have noticed when on full lock (three point or parking) theres a kind of bump/clunk from the axle/wheels as if something is catching then releasing. Car is totally standard on 16" merc wheels. Any thoughts anyone?

Check out the seller of this Smart Car on eBay. The highest bidder is currently 'breakdance69' but if you check the feedback of 'breakdance69' he had previously attempted to sell a Honda Prelude and had the following in his item description "WE ARE ACTUALLY SELLING 2 CARS, THE OTHER IS A "SMART"...