350Dave

The full tank noise does not bother me, just as long as I keep getting 25+ MPG I could not care less...

toneman

Maybe I'm not following the logic completely, but if the above is indeed the case...then wouldn't it make that noise only once per full tank? On my ES w/ a full tank of gas, I can repeat the clunk at will, except if I accelerate very gently/slowly from a stop...at least until the gas tank goes below roughly 3/4 full or so.

ChipM

Not necessarily once per tank; believe it has something to do with pressurization so it happens throughout driving cycle. However, mine is not necessarily "at will" on the RX

micosan

Was there a final answer to this question?

garsarno

Never heard any clunk from the rear gas tank area, whether full or not.

zhivuyatut

Mine is definitely making this thump. I was dismissing it as some cargo dislodging and hitting trunk walls, before realizing I don't have any cargo. I did not pay much attention to this before, but now that I know it would be haunting me.
I did not get the correlation with full/empty gas tank yet. Simple sloshing of gas in the tank would not do this. But it is conceivable that a wave of gasoline in the tank hits some baffle or rushes into some tight corner, making a hydraulic shock.
I am curious too if somebody did get Lexus to acknowledge the issue. None of my previous vehicles did this.

garsarno

Could a baffle be loose?

pestleman0

I'm experiencing the clunk.

jinnjia

same here, I have the exact same noise, rather than "clunk" I think more of a "thump".....

kewl

This is an old issue, first ID'ed back in 2007. It is, as someone said earlier, likely the float hitting the top of the tank when the tank is full. Dealer's everywhere say it is normal and there is no fix for it...as of now, and my guess is there never will be one from Lexus. It is nothing serious...just another noise source - at least while the tank is near full. Once you use a bit of fuel it will go away until the next fillup.

micosan

This noise is really annoying. My dealer also said it was normal. I am hoping someone is able to definitively determine the cause of this noise. Meanwhile I was looking at suspension components which I thought might cause the noise. Hopefully the attached images might provide some insights to knowledgeable members who could guide us to possible solution if these components are the cause of the clunking noise. The gaps shown in the images are created when the car was lifted at the left rear jack position.

I am guessing there may be some nose diving during a stop causing the rear of the car frame to ride up and cause a gap between the frame and rear suspension cross-member support, and also between the cross-member and the stabilizer bar support bracket. Once the car starts moving forward the rear of the car frame sits back down closing all the gaps which causes the clunking noise.

It would be great to hear from others about my speculation and possible solutions. Thanks

Suspension Component link http://www.trademotion.com/partlocat...layCatalogid=0

Jimbo68

micosan, thanks for the work on the suspension. I have the same noise, sometimes pronounced. Don't know for sure, but it may well be gas movement in the tank when almost full. It isn't a float, that not the way it works. I think it may be a baffle design flaw that doesn't address the forward and backward movement of the gas. I will be checking on the noise as the tank gets somewhat less full.

Jimbo68

It's definitely a full gas tank issue. The thump in my car went away after a couple gallons of gas had been used up. A poorly designed baffle is more than likely the reason. Just my two cents.

overclock

I just turn up the radio and I don't hear anything.