ColdFusion

iTrader: (2)

Recently in my '06 IS350 I've started to get this weird fluttering noise from my engine bay. It's loudest when the engine is revving from about 1k-3k RPM, but it's VERY noticeable at around the 2k RPM mark. I originally didn't think of this as a problem, but today my friend riding in my car even heard it, and it's been getting slightly louder/more obvious in the past week.

The noise seems to be rev-induced (meaning, it'll get noticeable when I press down on the gas pedal during acceleration or in neutral). Since in my hands the alternator was changed (only 200 miles after buying it), but the alternator belt wasn't swapped at that time. The car is not sending any codes to me, so I can't pinpoint exactly what problem it is. My first guess might be the alternator belt, but past that I have no idea.

I've provided a video below - you might have to turn up your volume to hear it clearly (it is VERY clear in the cabin if there's no audio or exterior noise coming in). Has anyone else experienced this sound before, or can any other engine techs/experts chime in and let me know if the problem is severe?


(Yes, I know, my TPMS sensor is dead, it's on my to-do list )

Thanks for reading, this community is awesome for all the help you've given me

carlos3366

Sounds like a lose catalytic converter or muffler.

Gville350

iTrader: (10)

Hopefully exhaust leak. BUT, it could be the beginning of a spun bearing. Is the noise coming from the engine or under the car?

ColdFusion

iTrader: (2)

Would I check for this under the car?

It seems like it's coming from the engine. I haven't had the time to pinpoint it, I'll try to get a clearer answer tonight.

ColdFusion

iTrader: (2)

Update: did a spark plug swap today (hasn't been changed since the car was bought...), noticed the plug closest to the passenger side firewall almost had the top bit completely eroded out. Other plugs were in great shape though.

I also inspected the alternator belt; there were a TON of small stones within the insides of the grooves, but no marked belt damage was seen. I don't know if this would cause the sound (I didn't think so).

After these two changes, the sound is still there, but it's less noticeable than before. One of my friends mentioned it could be a problem with the vacuum lines going into the intake. I checked all the tubes going into the main air flow tube or whatever it's called, but I didn't see any cracks or damage.

Has no one else had this kind of sound before? I'm tempted to take it to a friend's shop tomorrow to see if they have any input.

Gville350

iTrader: (10)

Can you post a picture of the bad spark plug? The noise could be what is causing the plug damage.

ColdFusion

iTrader: (2)

Sure.





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The last picture shows the most worn plug. The rest of the plugs actually don't look too bad.

I'm heavily assuming these plugs haven't been changed since the car was bought (~115k miles now), since the previous owner didn't have any records for a spark plug change.

So I actually got a professional opinion today from a shop my friend knows, he says the sound seems to be coming from under the car. He mentioned it's possibly a worn rod bearing (is this the same as the spun bearing you're talking about?), but he couldn't know for sure unless he took apart the oil pan.

Is that a common problem for these engines? I searched and found a few threads regarding spun bearings, but I'm not too familiar with the part/process of replacing it.

MWIS350

Does the car feel like is bogging lack of performance. When acceleration.

ColdFusion

iTrader: (2)

Doesn't feel like it.

MWIS350

If still running good maybe it's not engine problem or something serious.

ColdFusion

iTrader: (2)

The metal shavings I found in my oil filter from the last oil change lead me to believe otherwise. I'd much rather have this problem fixed now rather than continuing to drive it until the engine destroys itself.

KIS350

Unfortunately metal shavings in the oil would most probably point to a spun rod and or crank bearing. You're absolutely correct in the need to have this fixed and not driving it until it is. It will destroy just about everything in the engine if it hasn't already. Sorry my friend it's a very serious issue when you have aluminum or steel shavings in your oil/oil filter. At this point an overhaul is needed. Might as well rebuild it while the engine is out. Possible requirements for your fix:
New crankshaft (if it's damaged from the spun bearing)
New bearings obviously...all new crank and connecting rod bearings for each piston
New engine block if the crank bearing spun...it could have damaged the bearing seat in the block
New connecting rods...at the very least the one with the spun rod bearing
New piston rings and seals
Master overhaul kit for all needed gaskets and seals for rebuild
New oil pump maybe...
Etc,etc...
While it's apart you might as well do clean the valves and polish the heads and grind the valve seats

Sorry man...huge job here if your mechanic friend is correct. And your oil is agreeing with him. I would maybe look for a used engine for it...might save you some time and money.

ColdFusion

iTrader: (2)

Thanks for the input, this is what I am fearing as the worst case scenario. I'm beating myself over the head right now for not paying attention to the shavings in the oil earlier; it's been driven quite a bit since that change.

Currently I am planning to get a second opinion on the car from another independent dealer, then most likely taking it to my local Lexus dealer for a proper diagnosis with their master tech. They quoted me $150 for the diagnosis, then if any work is done by them the fee will apply to the final cost.

Which leads me to my next question. I found two other instances here on CL where drivers had spun bearings, but I think one or maybe both had Lexus pay for their fix. This car is not under warranty, and I am the second owner; both of us have religiously taken care of the car and have not done any modifications to it whatsoever. I am curious to:

1. What exactly would cause this kind of problem, considering oil changes and maintenance were kept up regularly?
2. Is there anything I can communicate to Lexus directly that would convince them to cover the cost of an engine rebuild?

Thanks again for everyone's input. I'll get back and post what the dealer says once the car has undergone a diagnosis.

KIS350

Spun rod bearing






You can see the bearing rotated out of position on the crank end of the connecting rod.





You can see the damage to the crank shaft from the connecting rod bearing being spun.


This will give you a noise and steel in your filter... there are other causes of steel in the filter but I think your noise coupled with the steel shavings would point to spun bearing. Hope some of this helps.

KIS350

Sorry my last post was in the works when you posted...

Cause of a spun bearing can vary. Typically it's something that causes the bearing to become misshapen in some way...typically lack of viscosity and increased temperatures. For instance...little or no oil on that bearing would increase friction, changing the shape and fit of that bearing during operation, thus perpetuating itself into further friction...until the precise bearing clearance around the crankshaft becomes not existing and the bearing "grabs" onto the crank and rotates...then jams for a brief moment and the engines power and momentum breaks it free again...at this point the engine has sustain the damage and it's downhill from there. The bearing is now set to wear away quickly from all the debree and crankshaft damage. Car will still run...but will be noisy and will eventually breakdown as the crankshaft will wear out the bearing completely then you connecting rod will break...and most likely destroy the engine block with a broken piston.

Under normal operation with no mods and regular oil and oil filter changes this should never happen. If you and the previous owner have been decent with maintenance then I am unsure of what could've cause this. Dirt in the oil could cause wear an perhaps heat up and spin the bearing. Driving at really high RPM's for long durations could heat up the bearings...usually cars that have increased horsepower have this happen a lot due to improper engine work and bearings.

What's the milage of the vehicle? I would say Lexus will not be flipping the bill for this. But I will add it's a great project over the winter to rebuild the engine...and it will be as good as new when you're done.

I'm glad you're getting a second opinion. Even a third if you want...never hurts and there is other possible causes of your symptoms.

Best of luck friend. I'll cross my fingers for you. And please keep us posted.

PS...don't beat yourself up...if it still runs than you're okay...piston is still attached and everything. The damage was already done when the shavings are in the oil... so you haven't really lost anything from driving it.