mha002

hey guys,

i have a question...when i start up my LS460, i hear some rattling noise comming from the engine..sounds like rocks/sand? im not sure but it only happens when i start up the car..after that..the car is completely quiet and drives perfectly fine...any input would help.

thanks!

CRowe14

Have you tried having someone start the vehicle while you have the hood opened and engine covers off, which would enable you to have a closer listening point to perhaps better observe the sound(s) your hearing?
This may not be the case for you, but shortly after I purchased my car, I didn't hear a rattle on start-up, but did hear a faint occasional rattling sound while driving.
It turned out to be 2 engine cover rivets; 1 completely out bouncing around beneath the hood, the other was loose within its seated position.
Once that was taken care of the rattling was gone.

mha002

ill check that out this weekend! thanks for the info!

Devh

If it's a faint rough sound that goes away after about a minute which is more noticeable when the car is cold then I would not worry about it. All of the LS460s that I have driven including one that had only 14k miles sounded a little rough on start up and quickly goes away. I believe there is a little metal to metal contact on startup before the oil lubricates possibly because of the tight tolerances and thin oil that drains into the pan leaving less residual oil between the parts.

mha002

its less than a minute...literrally within 3 seconds of me pressing the start engine button...i hear the rattling only when the engine is starting..as soon as it gets started..the rattling stops and the car idles quiet.

Devh

The only other thing I can think of is the belt tensioner.
Do you notice the same sound if the engine is still warm and the car restarted.

Doublebase

It's probably the rockers hitting the hydraulic cam followers, sometimes it takes a minute for the oil to fill them up and you get a little valve train noise for a few seconds. I get it once in a blue moon.

mha002

hmm, it doesn't make the sound when the car is warm...only when cold or if i havent started the car for a while.

mha002

hmm, does it sound like a few grains of pebbles or sand in a tin can that rattles for like 2-3 seconds?

Devh

That's what a bad tensioner sounds like. The only way to find out is to remove the belt and start the car. If the sound is gone then it's the tensioner.

CRowe14

And doing such is pretty easy. Just remember the looping pattern, and be sure to use a socket with a lengthy handle for leveraging the tensioner pulley.
May as well take a good look at the water pump while your there.

Devh

Great idea to spin all of the pulleys for noise and for play.

CRowe14

I couldn't agree more, which is exactly what I did while I was doing the water pump.

superdenso

Hello MHA002

You can try using a quality 5w30 weight oil. My personal favorite is Royal Purple. I haven't tried Mobil One's FullSyn 0w30, but that would be my second choice. Please, post the results after your chosen adjustments/checks.

mha002

What exactly would that do?