After an initial start up, upon mild acceleration my engine makes a consistent "knocking" sound. At idle it's not noticeable but when a little load is imposed with acceleration it's noticeable. Not pinging, but a distinct knock, a deeper consistent knock sound similar (gasp) to a rod knocking sound. As the car warms up the sound diminishes somewhat but is still to noticeable for me. Car has 9200 miles on it, and I will take it to dealer soon for 10k service and particularly to get it documented that I'm concerned about it. It should be velvet smooth and quiet............ and except for that sound it is. Anyone have similar sounds?

 

Yes, I have that harsh engine noise in our 2008 RX with only 8000 miles when the engine is cold. My understanding is it's a pretty common "complaint" with this 3.5L engine in the RX. My 2 friends with this same engine in their ES350 don't seem to have this issue for some reason. My personal feeling is the noise is really not a "knock" but rather valve train clattering exaggerated when the engine is cold but diminishes when it is warmed up. Yes, the noise quiets down considerably after it warms up but it never goes away. It has been something my wife and I have a hard time getting used to after acquiring this RX because our two other Lexus sedans (one's a 1994 ES and the other a 2000 GS4) are so quiet and exhibit none of this engine noise regardless of whether the engine is cold or not. We complained about this noise to the dealer during servicing and were told this was a common problem with the RX and there's not a fix to quiet it down. The new 2010 RX seems to have this same issue (it has the same 3.5L engine) but the factory may have added more noise insulation to quiet it down somewhat. Let us know what you find out from your dealer.

 

Are you using Premium Fuel? Using Regular octane gas may cause knocking in high-performance engines. Also if this is a recurring issue, definitely get it checked at the dealer.

 

I can assume u are using Premium Fuel, at least 91 Octane. I try to use 93.
There is talk about the valve train noise too. I have heard that from the dealer & others, makes sense to me.

 

This is a known issue and happens with the 3.5 L V6 starting with the 2007 model & up even if you use the recommended 91 Octane fuel. The noise goes away after the engine warms up. May be that is the reason Lexus added more insulation on the '10 RX.


In the ES & other car models the engine is little bit far away from the front seat compared to the RX.
Still do not understand how come Toyota/Lexus cannot fix this "problem".

 

Thanks for the responses. Re the fuel? I have experimented with regular 87 and premium 91 (the highest in Calif) running 3-4 tanks of one, then the other. Truthfully I can't tell any difference on mileage or performance, although we are pretty easy drivers. From prior experience with other cars I know what the pre-ignition "ping" sound is like, but my situation is a very regular, much deeper knocking sound. It is sounding like many others have encountered same situation. Isn't this 3.5 engine also used in Toyota Highlander? Wonder if they experience the same sound?

Scout356

 

I have an '09 RX AWD bought this March and haven't experienced any deep constant knocking sounds. If it's not the fuel then I'm confounded . I'm guessing your climate is quite different from mine. So far in NYC, I haven't had an especially "Cold Day" (ie: Below 32 degrees)

 

This seems to be a common trait of the Toyota 3.5L engine. I have an '06 Avalon and an '09 RX350. Both have the 3.5L engine and both exhibit the same knocking or "dieseling" sound at startup. Fuel octane rating does not matter. The engines do get quieter as they warm up but the 3.5L is definitely not one of the smoothest running V6 engines out there.

 

Pre-ignition is referred to as knocking .. this phenomenon happens when the engine head gets hot. Fuel octane rating can enhance or reduce it.

The thing being discussed here is lifter noise ... which is part of the vale train. The lifter noise resembles diesel truck noise and is more apparent during cold winter mornings, right after the start. The oil circulates and fills up the lifter as the engine runs. This noise is more apparent when you use synthetic oil. It is annoying but part of how the lifters work. So just take it easy and keep the engine rpm below 2500.

Salim

 

It happened on my 05 Scion 2.4L engine too, with synthetic oil, sometimes it gets darn right embarrassing exiting the garage on a cold morning start.

 

I hear that as well in our 09 rx. I brought it to the dealer and they told me there was nothing wrong. I use 91 gasoline so it cant be because I'm using cheap gas

 

Also, be sure to warm up your engines. It puts so much strain on your engine when you just start it and go.

 

^^ this is debatable.

Current thinking is as soon as lubrication is functional (should be 3 sec or so), the engine is capable of producing more than min required power. Then the objective is to reach the optimum temperature quickly as possible. So by adding load (useful work ... driving off) you will get to the optimum temperature quicker.

Note there are other things that do not reach their optimum temp by idling [like transmission fluid.

That said, one should drive at lower speed as due gearing, you will be at high engine revs area.

Salim