I have been noticing some slight rattling/faint screeching sound coming from the engine area when under load. My car is a 2003 GS430 with 89k miles. If I were to rev the engine while parked I cant replicate the cound but once the engine is under load, the rattling can be heard very slightly. I assume under load more vibration is taken into consideration and is making this noise. I have not had the timining belt or waterpump replaced yet, but will have that done next weekend at Lexus.

Looking for input from other members if there are certain areas I should look into. The car is stock engine wise. During cold start ups, I've been having some noise from the serpentine belt which goes away after 5 mins. Inspected the serpentine belt and it appears to be in good shape. Was replaced with OEM Lexus belt at 60k miles about 3 years ago.

Please let me know your thoughts. Thanks!

 

To replicate it, try revving (by hand with TB) very little, meaning barely move the TB and letting go quickly; only move like an inch or half inch, I bet you'll replicate it. If its what I think it is, its probably some engine knock.

If not that, possibly need a valve adjustment.

 

Thanks I will check it out. Have you had engine knock on yours? What have you replaced to get rid of the knock?

Honestly it sounds like something under the hood may be loose.

 

Yea, I have a slight knock caused by Up until a month ago, I never knew what the sound was, a neighbor mechanic says its knock, but I'm not very sure thats true because its very slight, more like a deep clicking sound coming from the plenum area, thats why I'm thinking more valve adjustment. Only happens at about ~500rpm when I gas then goes away when I drive. Comes back when the car comes to a stop. IIRC it goes away after the car warms up. When you check, try to pinpoint exactly from where its coming from, thats why its best to rev by hand with the TB, the only way to pinpoint exactly.

 

Yeah it definitely does not sound like engine knock. I've searched at it appears some other models have had this rattling/ringing coming from the exhaust - y pipe area.