GS400 engine noise

Does the engine still run smoothly once the noise starts? Does the noise get louder on acceleration?

My first thought is the 'gravelly-sounding noise' could be a connecting-rod bearing although with only 35,000 miles (I assume those are original miles?) it seems kind of remote that it could be a rod bearing but anything's possible. I also thought, even more of a remote chance, that it could be a wrist pin.

Have you tried putting in 10W40 or 50 oil to see if the problem quiets down? If it does, you're really only masking a potentially very serious (and expensive) problem.

My advice is to take it to a mechanic you can trust first, then if he can't figure it out, go to a dealer.

Also, try calling/e-mailing Pat Goss of "Goss's Garage" and "Motorweek" (on PBS) or Tom and Ray Migliotti ("The Car Guys" on NPR on Saturday or Sunday mornings). Pat Goss helped me with a problem I had with my van before taking it to the service station.

The engine always runs smoothly; that's not a problem. Because the noise is pretty subtle, I can't hear it in the car, so I can't say whether it gets louder on acceleration.

Yes, those are original miles. I spun a rod bearing on a Blazer years ago (with 20,000 miles on it!) and you could hear that rapping a block away. I would be really surprised if the problem were a rod bearing or wrist pin.

Lexus prefers 5W-30 oil and permits 10W-30. Overhead-cam engines don't like thicker oils because oil takes longer to reach the cams on startup. (These oils also void the warranty.) I use 10W-30 because I rarely drive the car in very cold weather. I would expect to hear similar noise if I tried 10W-40 or 50 oil.

Thanks much for your advice. At this point, I'm suspecting some wear in the overhead-cam timing chains or other cam-related mechanism. Even though the car is out of warranty, and depending on the diagnosis, I may lean on Lexus to pick up some of the repair cost because of the low mileage. Thanks again for your thoughts. John

Noises are difficult to diagnose without actually hearing them first hand. Check the power steering fluid level - if it is low, the pump can get noisy. Also, if the PS fluid level is low, check for fluid leaks.

A loose timing belt can make noises, as can a failing water pump, although water pumps tend to leak before they make noise.

Your best bet for a proper diagnosis is to have a competent technician listen to it.

Belt noise!

Common irritation.