Joe G

Is any one experiencing a cold engine knock? I have a 2010 RX350 with 18k miles. All oil changes were done by the dealer using 0-20 sinthetic. Lately noticed an engine knock that comes in on a cold start and goes away on warm up. Dealer clams its a piston slap and is normal due to teflon cylinder walls. He claims there is nothing they can do! He said its documented with Lexus and not to worry, the engine is under warranty. We own another 2010 RX350 with almost same mileage, same services, and no engine knock.

MEP7557

Mine makes a knocking noise for about 5 seconds, if that, on a cold start. I do live in AZ,

happy1977

Man, I do hope that this engine knocking doesn't cause any long term problems as we keep our cars, and by that time, warranty is gone. I'm @ 11K mi already in less than a year and the higher mi I go, the more paranoid I get.

Cruiter

Happy, while some seem to have it and others do not, Lexus say's it isn't a problem. So if you have it, then document it with your service dept., and you should be OK. While we've heard of it, I haven't heard of it becoming a reliability issue yet. And that's good news.

MX5NES350

Ah, the "diesel knock" on start-up. My 2007 ES350 had it and it would calm down after a few minutes of driving. Some of the RX's have it as well, however, IIRC the issue has been corrected in the 2012 year - how I do not know. It's not been a reliability issue and the noise has been present in the 350 series engines since their inception.

sweetboy02

I have it in both Lexus and Toyota car. Thought it a common thing.

kwbuggy

Have you been using 91 octane or higher fuel? I'm just wondering since a lot of posters (including me) here have had no problems with using 87 octane. I know that pinging is the usual result of using low octane but was wondering if it could also cause knocking on start up.

Alpy64

You should knock at the Lexus door (dealer/garage) and ask him to solve the problem just because a 6 cylinders (except diesel perhaps and even, not sure at all) does not knock when starting. The engine as a problem, it's mechanical not more not less.
What he said is not true, just because he does not want to solve it, to be embarrased and to contact Lexus US.
Insist and send letter to Lexus US and you will see that things may change.

mkeeney

Octane won't make any difference at idle. The octane number only comes into play when the engine is under a heavy load - hard acceleration, pulling a trailer, etc. At idle the engine could probably run safely on something like 79 octane, if it were available.

A point I don't think anyone has mentioned is that Lexus/Toyota changed to hydraulic valve lifters on the 3.5 engine. Some of the noise heard on cold startup can be attributed to the valves ticking before the lifters are fully pressurized. The switch to 0w20 oil would serve to amplify this condition since the oil is even thinner when cold. If you've put high miles on a previous generation 300 or 330 engine, you've probably heard your engine ticking and had to have the valves adjusted. The new hydraulic design eliminates this maintenance requirement.

Alpy64

It's maybe right mkeeney but why this case so isolated in forums for RX 350?

sightdev

this is all 350s as they are all same engine [with minor differences with some being DI]. I read online that Toyo did some improvement to reduce the engine noise [2011/12 and newer] and other internal engine components for durability. noise is more noticible for those park their vehicles inside the garage/under ground parking/late at night in quiet streets etc. noise does lessen when it reaches operating temperature but tick/tack never goes away. it does sound "crappy/cheap" but its not suppose to have any impact on longevity.

markrivers

i haven't experience it on our RX.
and how cold is a cold morning? 32 and below?

sightdev

most noise occurs when first starting after vehicle has been parked over night regardless of temperature, "cold start". some will hear/observe more than others but same sound regardless its ES/IS/RX/GS and other Toyo models with 3.5 V6 engine. note, there were no tick-tack noise on 3.0 or 3.3 on any Lexus nor Toyo as far as I can remember. I think 3.0 V6 from earlier Lex/Toyo was probably the quietest engine I have ever owned in a vehicle.

Evitzee

Neither my IS350 or RX350 has ever experienced any cold engine knock, it is just tolerances in various engines that sometimes produce the sound. Don't worry about it.

Joe G

I know everyone is telling me don't worry about noise even the dealer. It is documented with them. Cruiter even mentioned he hasn't heard of a reliabily issue yet, but look at the whole picture. The "piston slap" was not present at lower mileage. Its present now. There must be some clearance between piston and cylinder wall. (some wear). I feel that there will be more clearance at higher mileage. Do you agree?