snomuncher

Here's the new mystery. The 2010 RX350 has been parked in the garage for about six hours. I'm working on another project in the garage and suddenly hear the sound of an electric motor start to run. I look around outside to see if a neighbor is working with some power tool- nothing. Could it be an appliance in the house- no. I go back out and walk around the garage a bit and notice the sound is coming from the rear underside of the Lexus. I poke my head near the rear wheels where it is the loudest and just as I go seek the creeper to investigate the noise stops. All told, this motor ran for about four or five minutes. Anyone have an idea what this might be?

rcy

Yes, something to do with the emissions control. I think it's the charcoal canister being purged or something. My 2006 RX400h does the same thing. I think there's even a TSB regarding this..

garfull

its the emissions evap system purging itself. my service rep check last time i was in and said it was normal even after the car has been sitting. i think its even mentioned in the manual somewhere.

diesel60

Thanks for the post, I've unpluged everything in my garage trying to find this noise. Telling my self it's no the car. Lol

MartyE

This noise is described on page 22 of the 2010 RX350 Owner's Manual in a section that's aptly named "Noise from under vehicle after turning off the engine".

Johnny

Yes, all cars made over the last ten years do this shortly after the ignition is turned off to handle gasoline vaporization caused from a still-warm engine cooling down, however in recent years the sophistication the EVAP is such that the motor that direct fumes to the canister can start up even hours after shut down permitting the vacuum in the engine’s intake manifold to draw in fuel vapors.

During the canister purge's cycle, the system draws this vacuum through the carbon canister and allows fresh air to enter it. The vehicle’s Powertrain Control Module (PCM) determines the duty cycle of the purge solenoid. The purpose of allowing fresh air into the carbon canister is to oxygenate the stored hydrocarbons (HC) before they enter the engine, allowing for more efficient combustion. The mixture of HC and air being purged from the carbon canister is monitored closely by the PCM to assure that the lowest possible effect on vehicle tailpipe emissions is maintained.