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GS400 engine noise

I own a 1999 GS400 and recently noticed a gravelly-sounding noise at the front of the engine. The noise isn't loud enough to be noticeable with the hood closed. At first, I thought the noise was coming from the idler pulley that puts tension on the accessory drive belt. However, after placing a stethoscope on the pulley, that's not the problem.

I let the engine cool for a few hours and restarted it. On restart, the noise was not present, but it returned after running the engine for several minutes. That pretty much convinced me that the problem is internal to the engine and that the noise can only be heard after the oil warms and thins out. I use 10W-30 oil, which is acceptable according to the owner's manual, and change it every 5,000 miles. The car only has 35,000 miles on it.

Before I take the car to my super-expensive Lexus dealer, I wanted to get this group's opinions on what the problem might be. Thanks in advance.

John

Reply to
do_not_reply1
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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.

Reply to
Mike Piacente

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

Reply to
do_not_reply1

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.

Reply to
Ray O

Belt noise!

Common irritation.

Reply to
Jerry Whitaker

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