flyfishman

Have a '05 GX with ~ 20K miles and every so often upon a cold start-up, the engine emits a noticeable helicopter type noise (piston-slapesque) when taking the car out of park into reverse/drive. Completely goes away once warm, but very concerned this could be creating undue wear in the engine and become a significant issue down the road. Asked the dealer about it on the last oil change and they said they would check it out (they indicated that what I described had been an issue w/ other GXs) but when I picked it up all of the service guys were gone and no notations as to the problem. Obviously, I will take back in pretty soon to get a complete diagnosis, but wanted to see if others have experienced this problem or have any insight otherwise.

Aristanet

Mine 07 does the same thing - i had it for a week and noticed that from day one. Noise completly goes away once the car warms or in a minute or so.

RC1818

is the sound coming from directly under the car towards the middle if so it could just be the catalytic converter shield/pan touching while its warming up.....slight adjustment should do the trick, its just rattling, nothing to worry about!!

Salvator

I occasionally get a similar noise... cold start, kind of a ticking or knocking... I was wondering if it was a valve lifter noise, used to hear that in our old '69 Buick back in the day... Please let us know if you find anything out from your dealer...

CVsIS250

don't your joints crack a bit in the cold when you first wake up!

alsilverbullet

My 06 GX with only 8K did the same thing one cool morning. It sounded horrible and was blowing white smoke out of the tail pipe. It was the wierdest thing. I shut the truck off waited a minute and then cranked it back up and it still made the clunking sound but not as bad. After a few minutes of idle the sound went away. It has never happened again. I took it in for my 10K service and was told everything is fine.

flyfishman

Seems to be coming from engine compartment and only makes the heavy knocking noise when I put in reverse from park position (have not noticed it as much when I engage drive out of park). When in park the sound is muted (mainly because the RPMs are higher in park on start-up) , but really noticeable when you put in reverse. Usually this is after a couple days of no use. It has done this in both warm and cold weather. Kind of strange. I will inquire about the cat converter when I take in, but I am not holding my breath that it's the source.

flyfishman

Mine did this once too (heavy vibration - much more than my recurring knocking issue) with less than 5K miles. Scared the ***** out of me, has not done it since. Almost sounded like it had bad gas. Went away on second start-up.

PRSUIT460

iTrader: (3)

I think the noise you hear at cold startup is piston slap.

I6turbo

iTrader: (1)

I think piston slap would be the same every time on startup -- make the same noise until the skirts warm up and expand to better fill the cylinder bores. Instead, what most of the descriptions here sound like is that the engine happened to stop in a particular spot in its rotation where one or more of the oil holes in the crankshaft happened to be lined up with the supply holes in the main bearing saddle(s). As a result, the oil was able to drain out of the galleys in the block and crank/camshaft bores, running back into the oil pan. So, what happened as a result was that the oil system kind of 'lost its prime,' so it took a few seconds upon startup for the pump to pick up the oil and pressurize it back to the bearings. You often hear this happen when the oil is changed in some engines -- you drain the oil and the pump empties as do some of the oil galleys. You leave it sit for a little while to allow all the oil to drain out of the pan, then add new oil, start the engine, and the bearings and valve train rattle for 2 or 3 seconds until the pump pressurizes the oil system.

I'm not certain that this is what happened, but it's something that I've seen on other engines once in a while over the years. The engine has to happen to stop at just the right (or wrong) place in the rotation for it to happen, and that by chance happens pretty rarely, hence the 'once a year' occurrence.

Salvator

I concur with your assessment... it does sound kind of like when you first fire it up after an oil change... I don't however, like what that means, especially in cold weather... Mine happens more frequently than once a year... In fact, I've heard it on average probably about once a month... How much damage is this doing to my engine? Probably not much, but it doesn't seem like something that ought to happen that frequently... Pure surmization on my part, but I wonder if it has something to do with the 5W30 oil? Might it be that that oil "drains off" too easily?

I6turbo

iTrader: (1)

Yeah, I'm not sure if there will be any measurable consequences, but I definitely don't like the sound of it either. I've heard it once on my LS in the year or so I've owned it. Over the years I've heard it a time or two on most every vehicle I've owned. I'm somewhat comforted by the fact that I heard it pretty often on a 460 Ford I had many years ago, and that thing ran perfectly until it had 230K miles on it (well, if you can consider getting 6 MPG running perfectly).

love_lexus

I noticed my 06 GX having the same issue, is there is fix from dealer?

cssnms

It's normal. Common in Toyota V-8 engines. Likely culprits are the fuel injector solenoids and or the common cold clearance noises from the valve train.

If it's a loud knocking as opposed to a ticking could be the fuel mixture, try a different gas or higher octane. If the engine abnormally vibrates when you hear this sound go see your SA.

RXGS

iTrader: (2)

Just a side note, our lx470 does the same thing along with others, and it has been stated as normal with no damage done