2005 Ultra, 145k miles... I was accelerating a bit briskly yesterday morning and my LS430 started...buzzing... at higher revs (4k+) until I reached speed. My son said he thought I had gone over a rumble strip. But more like a buzz saw, and definitely from the engine (not suspension, etc.) . It happened again near my house when I got brave to not feather the accelerator home. Then it stopped completely, with normal acceleration noises, when I drove it onto highway ramp to test it a 3rd time, and has not come back. However, the car then (immediately after, in my driveway) got a fairly loud whirring noise at idle that varies a bit in frequency with engine speed. My 4 year old water pump always made a tiny bit of noise, if you listen, but this sounded like a more serious thing -- though not like the engine was about to rip apart like that buzzing.

Oil was changed 8 months ago with about 3k on it and looks fairly clean (yes, a bit overdue). Coolant was low in overflow tank and added perhaps 25 ounces of the pink long-life in case to bring it up near max line. It has been low a while (not sure why) but not missing. Given no coolant added in years, I think it is OK. Car never overheats and is not obviously or quickly losing coolant.

This morning the whirring noise continued, and I drove car to a mechanic. By time I got there the sound had pretty much gone away. At end of day he said he did not find an obvious issue. He'll redrive it in morning. The whirring happened once before, but restarting the car or driving it a block or so fixed it. I changed the serpentine-belt once years ago (will have to see when) but probably not more than 6 years/50k miles ago. (I have owned the car almost 13 years). I thought perhaps water pump since coolant was low (could not see any in overflow window) but it only needed a bit and level is holding fine -- and water pump has under 25k on it and < 4 years, along with the timing belt.

Shop mentioned an engine "air pump" / injector of some sort but admitted that was pure guessing so far, and I'm not sure what that referred to.. And it does not explain the loud buzzing as I revved up, which is what really worried me. I feared hard internal engine damage when I heard that, so really happy it resolved (vs. say, the engine seizing).

Any thoughts? I am not sure on reproducibility, which may or may not be a good thing... I will update if I learn more. I have had codes before (warning light for 1 new cat and new y-pipe almost 3 years ago) but never anything like this. Car is 17 years old but drive train has been impeccable until now, and I put on just 3-4k a year so hoping it would last...

 

Power steering.
Fluid is more viscous in the morning when it’s cold outside so it doesn’t flow easily. The whine you hear is the PS pump being starved of fluid. I’m guessing once the car warms up the noise goes away…?
Check the level, use the cap/dipstick, as the reservoir is likely stained making it visually misleading. Prob not a bad idea to change the fluid. Use Dexron ATF not conventional power steering fluid.

 

Interesting thought, thanks... I never actually check level and not sure where to begin (will have to have a look when I get the car back, I assume just a cap like brake fluid that I can remove)! I actually had fluid replaced there last year for first time ever just pro-actively. All others fluids have been done (even differential fluid every 60k). But what you are describing matches my conditions to a degree (the whirring started after that other issue but happened again next morning when cold). If low, hope it is not a big deal (leaking etc.). But this gives me something to consider, so thanks.

 

Just an update. Back from mechanic and nothing found. Car seems fine to mee, too, power steering level was fine too (and I had replaced it last year). Did have that whirring sound briefly and not as loud once more after I got it back, and not on first time, but acceleration is quiet and smooth as always. Since then perfect so far. Nothing like an interim issue to be frustrating. I have to remind myself car is 17 years old. A more obvious fail would be easier to fix. Other than a dead battery or damaged tire, it has never left me stranded. I hope that continues. Identifying groans and glitches on an old car (if no codes thrown, etc.) is not always easy, is it? I like the car compared to many new ones I have driven. Great headlights, great visibility. Hoping it's fine. I would love a newer car with added safety the with all the attributes of this one, but I got the Ultra specifically for the adaptive cruise back in 2009 and love it. My Cadillas XTS (wife's car) cannot compare: screen is too low, controls not as intuitive (distracting), headlights not as good. Newer but not better except it does feel tighter/suppler due to being so much newer. I can't see myself in an LS500 even if I could afford it. Didn't love my es350 as a loaner 2 years ago. Argh... well, the car seems perfectly fine for now!! Here's hoping for a few more years. Closest thing I ever tried to this was a Genesis G80 (never tried a G90). Really liked it, but next car I would want better MPG, so perhaps hybrid or consider electric if it was the right car.

 

Two thoughts:
1. It sounds like you have maintained your power steering fluid, but just a friendly reminder that we've seen cases where the reservoir had gotten stained and appeared full when actually empty. I doubt that's the case here, but thought I'd mention it just in case.

2. I'm thinking serpentine idler pulley may be the cause of your noise. When mine went, it led to a very loud whirring noise that subsided as the engine warmed up. These are cheap and easy to replace, and they aren't unheard of to fail.

Good luck figuring it out.

 

thanks, LexRex. It occurred to me belt could be bad, but I had nor thought about pulley, which is funny because when I do my timing belt I always ask to do the whole kit, which incudes tensioner or whatever...My question back is this: can idler pulley suddenly fail, leaving me stranded without a functioning serpentine belt? If a relatively small job for a mechanic, and it can fail suddenly leaving me stranded (what does it power, the alternator? power steering?) I would consider replacing it proactively if it is a candidate as the cause.


Thanks again.

 

If the pulley seizes, it will throw or break the belt, and then you can be stranded.

But I wouldn't throw money and parts at having a mechanic swap the idler unless you had confirmed the likelihood of it being the problem.

If I were you, I would try a stethescope (or paper towel tube or wrench to your ear) to see if the noise is coming from the area of the idler pulley. Or, you can also slip the serp belt off and see if the idler spins smoothly (tensioner too).

if the problem is either pulley, it's a quick DIY swap for a new part. Or if you're feeling mildly adventurous, there are numerous posts on this forum about just swapping the bearings instead of the whole pulley.

 

I wanted to update in case anyone else gets intermittent weird grinding (like metal being machined... ouch) sound under acceleration, even though it only happened on one day. Mechanic found nothing, but a month or so later, car died (started fading out, managed to get to edge of road).. I did have a warning light about a week before, but it turned off after 1 day. FWIW, from the behavior (llghts fading while running, etc.) I guessed properly that the alternator died. New alternator, new serpentine belt (alas, not sure about any idler pulleys) and the car has been fine a couple of months. Maybe that was the sound? It took some time after that before the failure, but throwing it out there...145k miles on the car. $600 at chain center for the alternator and belt.