I bought my RX350 last month and sometimes I notice a strange buzzing sound coming from the car while the engine is off. This noise can come at anytime and usually hours after I have turned off my car. It's difficult to isolate where it's coming from and can last just a few minutes. Has anybody else experienced this?

 

I think I may have heard this sound a couple of times also. And it's different than when the gas vapor purge pump is running. That usually happens right when I turn the car off, and then I notice when my headlights turn off after a few seconds, that sound goes away.

But the other day, my RX had been parked in the garage for several hours and I was going to close the garage door before retiring to bed, and I heard this noise that I couldn't tell what the heck it was.

I thought maybe something that was stored in the garage had been turned on or something and I walked around the car trying to locate the source. Well, after I started the car to move it further into the garage so I could close the garage door, the sound went away. So I'm puzzled as to what that sound may have been because it was a different type of sound than the gas vapor pump doing its thing.

 

I spoke to the service tech at the dealership today and he seems to think that it is the gas vapor pump. He said it turns on hours after the engine has been shut off when there's a 1/4 to 3/4 tank of gas. This seems to be the most reasonable explanation so that's what I'm gonna go with. Thanks for the responses.

 

On page 22 on the (2011 RX350) owner's manual, there's a section titled "Noise from under vehicle after turning off the engine." It says, "Approximately five hours after the engine is turned off, you may hear sound coming from under the vehicle for several minutes. This is the sound of a fuel evaporation leakage check and it does not indicate a malfunction."

HTH

 

Thanks for sharing the knowledge. Our 4 month old RX350 just did this for the 2nd time. This time 5 hours after the car was parked in the garage. To stop it, I simply started the engine and then turned it off.

I'm relieved to learn this is expected behavior.

 

Just went into the garage and I hear a humming sound coming from the back of the car. We had been out for dinner 6 hours earlier, came home, turned off and locked the car doors. The 2013 RX has about 3500 miles, completely stock, no wiring changes, no accessories added and has about 7/8 of a tank of fuel. I crawled under the back and clear as day can hear the fuel pump running (could actually hear it when I walked into the quiet garage).

So I start the car, back it out of the garage and run it back in and turn off the car and now the fuel pump stops. I probably would have had a dead battery in the morning if I had not caught this.

Will have the dealer check it out. I doubt there would be a fault code captured for this, but who knows. All I can think of is a sticking fuel pump relay. This should not happen at 3500 miles!

Has anyone ever experienced this unusual behavior before?

 

Normal behavior. Part of the emmisions system, I believe it is purging the tank. It is noted in the 1000+ page owners manual.

 

about 6 hours after turning off he car.

 

Can you be more specific? It is normal on the Gen III RX 350 and 450h to hear various pumps purging vapors (from time to time) after car has been shut down. That is by design, nothing to worry about. They should run for short periods only, not a 'continuous' run. Is yours cutting on and off from time to time or just 'running' continuously? If that is the case, you need to visit your dealer.

 

after 6 hours of sitting locked in the garage. For all I know it ran the whole 6 hrs+. When I restarted and turned the car off the fuel pump turned off right away. I find no reference to this in my manual after page 1000 or otherwise. I have never experienced this since buying the car new Aug 3rd.

 

My Owner's Manual states: Approximately five hours after the hybrid system is turned off, you may hear sound coming from under the vehicle for several minutes. This is the sound of a fuel evaporation leakage check and, it does not indicate a malfunction. Something to consider!

 

Our Evap systems do purging and pressure checks while the vehicle is off and on. What you are hearing in the garage is the EVAP system doing a routine check. I highly doubt it was running the whole time, but it will check at intervals up to two weeks with the car sitting.

Other systems that will run with the car off and locked that you are unaware of:

Smart Key
TPMS
EVAP

 

I just had the same experience in my new RX 350 and thought I was going to go nuts
trying to find the source.
Thanks for all the good information....I've had quite a few cars, and this was a first.

 

Had it happen as well on our 2013 RX. I've only noticed it once though. Glad to find this thread.

 

me too. the first time I heard it I flipped out a little.....$52K car that is already broken????? (I said in my head, of course). A quick google search turned up a thread on this forum about it, and I quickly joined!