In the last few weeks I've had this recurring sound under the hood. As soon as the engine starts there is a ratchet-like sound coming from the engine compartment. Somtimes it last for a second. Sometimes it lasts for .5 seconds. Sometimes not at all. But it only seems to happen in the morning after the car has been parked overnight in closed garage. Took it into my dealer. Leaving it for the weekend. He's gonna have his diagnostician call CA Lexus on Monday. Very troubling. Anyone care to guess what the sound might be? It almost sounds like the car trying to start when it won't turn over. It's hard to reproduce with certainty so I can see this as being something that is going to be hard to identify. Wanted to get a thread out here though just in case someone else might have this same problem down the line.

EDIT: And no, it's not the injectors. That's a completely different "clacking" sound. I know about that full well.

 

Hmmm.... you say broken teeth. Come to think of it, it did sound as if something was slipping (a belt ?) across some teeth or something. Had a distinctly platic sound to it though. Thanks for the suggestion. I'll take these with me when I talk to the service tech on Monday.

 

Cross reference for possible solution:
https://www.clublexus.com/forums/sho...77#post2562777