My 2008 lexus gs350 makes this clunking sound when I turn the steering wheel half way. It intermident so the dealer cannot replicate the problem to figure out what wrong.
You can feel it when it make the clunk on the steering wheel

 

Do you have AWD

 

No i have a rwd

 

did they put it in the air to see if theres play in the tie rod ends or ball joints

 

No the dealer just drove it and turn the steering wheel trying to replicate the clunk

 

The thing that annoy me is it not constant. It come and go

 

not sure this will help but my car is lowered

 

I would try and spray some dry film lubricant around the springs where they make contact . Check the sway bar links and bushings

 

ok I'll try that. But also the clunking noise happen when I am parked and turning the steering wheel. When I'm driving and turning I don't feel it

 

Did you purchase the car recently, or have you had it for a while? Also, was any suspension work done or new wheels/tires put on around the time this started happening?

Also, how many miles are on the car?

 

Had the car for 18 month. Car has 70k miles. Nope didn't have any new suspension work done and no new tires when it happened. Problem just started bac in july

 

I think SILENTM has the right idea – check all the bolts, nuts, bushings and ball joints on the control arms, steering gear, steering knuckles and shocks to make sure everything is tight and that there aren't any ripped ball joint covers. Also, check the inner tie rod boots for any rips or tears – a damaged boot can allow dirt to get into the ball joint and steering assembly and foul the grease.

Also, the early F-sport sway bars had clunking as a very common issue (it was a problem with the bushings if I remember correctly, and the redesigned bushings solved the problem) – so if you have F-sport sways, that may be the problem.

Could also be a wheel bearing starting to go bad, so it would be a good idea to see if there's any play in the front wheels.