Ls400 Rattle When Stopped In Gear

[Philip123]

I purchased a ls400 roughly a month ago today i was sitting at the traffic lights with the car in drive and my foot on the brake with my window down and I heard a rattling noise coming from the engine bay on closer inspection it looked to be coming from near the power steering belt and it also occurs when the revs are held roughly 200 rpm above idle in neutral and park it sounds like someone putting a coin ontop of a vibrating washing machine if anyone could help me or has experienced it too could you help please it's driving me mad! Thanks in advance

[steve2006]

There have been problems with the serpentine belt idler pulley with a dry bearing but this is normally a squeaking noise which goes after a few minutes and is more pronounced in cold weather.

What you could do is remove the belt and then start the engine and see if the noise goes, don't move the car in this state as you will have no power steering, AC or alternator drive ( the charge light will come on during this test)

If the noise disappears it will be one of the moving parts along the sepentine belt ( the above 3 plus the idler or auto tensioner)

If the noise remains it is coming from elsewhere so further investigation will be required.

A useful tool is an automotive stethoscope with which you can probe suspect areas, being aware of moving parts of course and then listen more accurately for the source of the noise.

Link below may help if you do need to remove the belt

http://www.lexls.com/tutorials/maintenance/drivebelt.html

[ambermarine]

Hi

When you say the power steering belt that leaves a lot of area as it runs round the air conditioner crankshaft alternator and power steering pulleys and is known as the serpentine belt.

The fact that it rattles both in gear and in neutral could illinminate transmission and there fore leaves you with two likely candidates the power steering pump and the a/c compressor.With the engine running at rattle speed get a high powered torch and look closely at the fastenings of all components related to the serpintine belt .if nothing shows check the radiator fastenings and the viscous coupling fastenings on the fan.After the engine as cooled down check all areas at the front of the engine for loose fastenings of any discription.

If you are no nearer to finding the rattle then you will have to start illiminating the items by degree initially using steve's removal of the serpentine belt this can be time consuming but nessacary as any rattles in the engine bay of a lexus ls400 are alien to the speices.

[Parrot of Doom]

I'd also check the exhaust manifold heatshields, you should be able to reach them from above the engine. They're only thin metal and would make exactly the sound you describe.

[LowriderUK]

My money would be on exhaust heatshields also.

[Philip123]

Ok well I checked the exhaust heatshield and I tried to remove the auxiliary belt, but when turning the 14mm tensioner bolt the bolt started to undo so I never removed it any advice? And also what should be the idle speed of my engine it's a 1996 Thanks

[ambermarine]

Ok well I checked the exhaust heatshield and I tried to remove the auxiliary belt, but when turning the 14mm tensioner bolt the bolt started to undo so I never removed it any advice? And also what should be the idle speed of my engine it's a 1996 Thanks

Hi Philip

the revs for idle are 600/650 rpm .

try this check

Put the Air conditioning to lowest setting this will send the compressor into full application, check if there are any changes in symptoms the revs will go up to 1100rpm and the clutch for the compressor will engage.

another possibility is the fastenings on the engine covers both under and over and the protection cover to the oil filter.

[Philip123]

Well I just started it up and when the revs have dropped down it idles at about 550 rpm so that might be the cause would that cause that sort of noise? The noise it makes does sound like if your in a manual car and you don't give it enough revs to set off what do you think?

[Philip123]

I found out that the rattle was caused by my tensioner pulley bearing being shot thanks for the advice