I just picked up my 207 ES350 from Lexus of Las Vegas after leaving it off for three days (over the weekend) to make sure it was good and cold to show them the ticking, tapping, knocking sound. The car has to be stone cold as the annoying noise goes away as the temperature gauge rises above cold into the warm-up process. You have to put a slight load (accelleration) on the car to distinctly hear it. The noise can go away in as little as 2-3 minutes and less than a mile. The noise started almost imperceptibally a few weeks after dealer delivery (late August) and has now gotten to be regular and annoying ... as our weather is getting colder.
It took only a minute for the Master Diagnostic Technician from Lexus to explain that this is a "normal" noise in the "350" engine. He called it "Piston Slap", also known as cold piston knock in the industry. He confided to me that these were his "words" and that Lexus doesn't like to use that term.
I recommend that you visit the website <www.pistonslap.com> and be knowledgable in this subject before having your technician write up your work order. Let me know the outcome of your service manager's response.
I have experienced "piston slap" twice during cold weather and when my ES350 was parked outside for several hours in the cold. It never happens when the car is cold but garaged overnight. I mentioned it to my service adviser last week during the 20,000 mile service. He new about it via a service bulletin and said he would address it during the winter and my next service appointment.
