wdtony

Hi, new here. I could use some direction. I am concerned with an engine noise.

Has anyone else experienced an engine noise like this or know someone familiar with this engine? I would like to narrow down possible causes.

5 months ago we bought a 2005 Lexus RX-330. It had 109k miles on it (now has 113k). There is a faint but noticeable engine tap/ knock/ tick coming from the engine. I think it has the 3.3l, 3gr-fe engine.

I have listed some observations:

The sound does not occur on startup, when the car is completely cold.
The sound starts after 5-10 minutes of driving or idling.
The sound diminishes and is almost imperceptible after another 10 minutes of driving.
The sound is only noticeable at idle.
The sound/tap seems to occur about 5 times a second at 600 rpm (idle)
The sound increases frequency with rising of rpm.
At approximately 2k rpm the sound cannot be heard.
If the vehicle is stopped after driving, allowed to sit for 5-10 minutes and then restarted, the sound will be loudest even though the engine is still hot.
The engine is quiet overall with exception of this sound. The fuel injector sound is the next loudest sound.
The sound doesn't seem to have gotten louder in the last 5 months but it may have gotten just slightly louder by my estimation.
I can hear the sound inside the vehicle and outside as well.

No other symptoms are present.

I had the timing belt, water pump, idler and tensioner replaced as maintenance and as a possible solution to this problem right after buying the vehicle.

The mechanic heard the sound but told me he wasn't sure of the cause. He and I agree that it sounds like an internal engine noise. It is not a pulley, idler or exhaust sound. The mechanic told me not to worry about it and it was a normal sound. He also said to start troubleshooting would get expensive. I am still concerned.



I have used a mechanics stethoscope and after listening at every engine point for several weeks, I cannot pinpoint the area of the engine the sound is coming from.

We spent our savings on this car and took out a loan and just found out we have a baby on the way. So we don't have much extra cash to go exploring this sound professionally if it is too costly.

My best guess at this point is that it may be something in the valve-train such as a worn shim, bad lifter or misadjusted lifter shim. I am hoping it is not emanating from the bottom end.


Does anyone have any experience with something like this or an educated guess? Any idea how much it might cost at the dealer to get a diagnosis? Thanks for any support.

nipponbird

In the first place: Welcome here at CL.
What I'm going to suggest, may sound like the observation of someone in the loony bin, but are you quite sure it comes from the engine? Make sure all other items that rotate like the interior fan are off when you listen to this sound and remember: the ABS checking system can make noises which can sound if it comes from the engine. Simply start with the most "silly" possibilities, before you strip the engine. These engines are known to be rock solid for extremely high mileages, they are not in the list of suspects easily, when it comes to noises.

Just to illustrate this: I knew a guy with an Alfa Romeo, who nearly had the whole car rebuilt to get rid of an ominous tapping sound, just to find out that it goes away if the interior fan is switched off - real cause: the fan sucked a little piece of grit into the squirrel cage.

robbyk

I had a engine noise similar to yours and I could not tell where it was coming from, I was pretty sure it was either engine noise or fuel injector noise. Lexus dealer replaced the fuel dampener.

LazarusLng

Where is the fuel dampener? I also have a bit of a tic. I have heard this same tic in 4 other 3.3 engines. I was,thinking injectors?

TriniLex

Do you smell gas fumes?

Bon

There have been LOTS of discussions about the noises of Toyota engines during warmup. An often discussed cause is piston slap that's a result of the short-skirted pistons used in these engines. This type of piston has less drag/friction/mass than previous designs and it results in smoother more efficient engines. The different warming and expansion rates of the pistons relative to the cylinder block are said to be the culprit. When everything comes up to temperature the slapping is gone. I avoid driving my engine hard/fast until it has thoroughly warmed up and a good indication of this is when the ticking stops!

wdtony

First, I appreciate all the posts. All ideas are helpful.

Now...... It does not seem to be the interior fan. With the car in park and running at idle, this is when I hear the noise.... tap, tap, tap, tap. It is louder outside near the engine. So it isn't anything like brakes, tires, suspension etc. I also don't believe it is a pulley because I had the entire timing circuit replaced and I am familiar with bad bearings sounds and it is nothing like that. I also crawled under the car a couple months ago and checked all heat shields, etc. just to make sure nothing was vibrating causing the noise. Nothing from the exhaust was the culprit. It is also not the AC compressor.

I did not have the oil pump replaced, so that is a possible cause.

The sound to me seems like it must have something to do with one of the cylinders. The sound increases in frequency with a slow rise in rpm at idle.

That said, I can't entirely rule out the exhaust among other things.

I will look into the fuel dampener. Did your sound come and go like in my description or was the sound always present?

I don't smell any gas fumes except what is normal coming from the tailpipe. Definitely no gas fumes from under the hood.

I can easily hear the injectors through the fuel rail with the stethoscope, the sound is definitely not the same sound or coming from that area.

Thanks for the bit on piston slap. It is very possible this could be the problem. I have read that piston slap is normal but other places online say it is bad and the engine will go bad. I also wondered if it is piston slap, why would it only occur in one cylinder. shouldn't all cylinder tolerances be the same? And if I stop the car, wait a few minutes and restart it at idle, the sound will be pretty loud again. So I was thinking there shouldn't be that much shrinking or expansion that quickly. This is driving me nuts.....ugh

The mechanic told me if it only does this at start-up and then goes away not to worry about it and it might be a loose wrist pin. But the sound doesn't go away like he said, in fact I don't even hear it at start-up until about 5-10 minutes of running the engine. That's weird to me.

Of course I am dreading this being rod knock. I have never heard rod knock start quietly and get louder over time so I am not sure what attributes to listen for when diagnosing rod knock. I have found online two associations with the sound I am having (mostly) which is an upper end issue like a malfunctioning lifter or lower end like a worn rod bearing.

I am going to make a Youtube vid of the sound over the next few days and post it here. I really need that so I won't have to describe it poorly.

Sorry, I know I am asking for everyone to be psychic here without all the needed info. We just sank so much money into this car that if it turned out to be a lemon and needs an engine rebuild...... we couldn't afford it. The mechanic said it was a great car and inspection was excellent.... but the sound isn't very loud and is intermittent.

Anyway, thanks everyone! and I will be posting that video as soon as I can.

wdtony

Ok, so I just listened to a few videos on this forum with piston slap, and the sound I have is absolutely nothing like that .

I think it is safe to say it is not piston slap.

Bon

So, do you hear YOUR piston slap? All of our engines have this noise during warm up. Some quieter, some louder, but it's always there during warm up. If you do hear yours and it's distinctly different/separate from the other noise you're diagnosing then I'm with you. It's a tolerance issue between components within the engine for sure (as it comes and goes during warm up). You have six cylinders, where one, or more, cylinders can be involved. For this very reason the sounds can vary a lot as it might be a front or rear cylinder(s). You'll read where some folks think piston slap is the end of the world (engine) and there's a lot of us who have many miles on our engines that have this and it hasn't caused any problem except for the aggravation of listening to it.

wdtony

When I start the car, everything sounds normal to me. The rpm's are about 800 to 1000 which seems normal and I don't hear anything unusual.

Then after several minutes of the engine running or driving, if I stop at a light or park and the engine is at idle I hear the distinct tap, tap, tap. The rpm drops to about 600 rpm and the idle is relaxed. As it runs and I try to listen and diagnose where it is coming from or what it might be.... over the next 5-10 minutes the tap/knock diminishes more and more until it is almost unnoticeable. At that point I can still barely hear it but it doesn't sound bad.

But then, if I shut the engine off for 5-10 minutes and restart the engine, the sound is back and much more distinct. I notice this sound a lot after going to the grocery and coming back out to the car.... it's aggravating... bap-bap-bap-bap-bap-bap.

Also, when the sound has diminished and the engine is running smooth, the loudest sound from the engine is the fuel injectors which have a distinct sound. That sound is relatively quiet though and sounds normal and smooth.

robbyk

Sounds like lifters to me but hard to tell.

Is the coming from the front cylinders or the rear cylinders?

wdtony

It sounds to me like it is coming from the rear cylinders if I had to pick. But I have listened with a stethoscope and can hear no difference at any point on the engine, including back/front, top/bottom.

I have made 3 clips and will be posting them here tonight after they are finished uploading to Youtube. Hopefully these will be better for a diagnosis.

wdtony

I started the car after it had sat all night, basically a cold start. At this point the noise is difficult to hear or distinguish from normal engine noises. Sounds normal right? Except maybe toward the end of the video.

wdtony

I drove the car 5 miles, stopped for gas with the engine off for 7 minutes and this is how it sounds when I started it again at the gas station. The noise is more distinct..... tap, tap, tap, tap. It gets more quiet as the car is driven and after several minutes of idling will also become more quiet.

wdtony

I drove the car 10 miles, went into the gym for 40 minutes and this is how it sounded when I started it in the gym parking lot. You can hear the deeper pitch when I put the camera below the vehicle.

Again, the sound can be heard distinctly. It is a tapping or knocking sound but gets more quiet as the car is driven and after several minutes of idling will also become more quiet.