A quick update
just finished a test run before the Alaska trip, 13500km round trip thru 16 states (including route 66), the RX300 was stable except for the following:

1. Had to add 2 Quarts of oil between oil changes, oil changed religiously at 5k intervals.
2. Rear light bulb failed and the indicator light came on. it was loose really, quick fix.
3. On my return and check up / clean up, i found water had leaked under the passenger side carpet from "not sure where" -> any pointers on resolution will be appreciated.
4. Had to add some coolant en route, watching now to see if this is a issue.
5. Thru some mountains (i.e North Cascades and Glacier NP) i felt a loss of power, not sure if this is due to low oil or some other reason. reading up on 'knock sensors" now ....
6. Thru the cities i had the CEL come on with Code P0136 indicating "O2 Sensor Circuit Malfunction" (bank1 sensor2), but this cleared on the highway. I have changed the sensor just before we went. Any ideas why it would do this?
7. Passenger side rear door lock is no longer obeying the remote commands. Guessing the relay issue is the culprit.

I am getting the feeling the RX is getting a bit tired and sluggish, it topped 335000km. Roughly i got 11.5lit/100km [20.45Miles/US Gallon]. NOTE - we were fully loaded with a roof box.

Re-thinking of taking the RX into Alaska due to the issues mentioned earlier (i.e. mainly oil issue and the loss of power) and (after speaking to a Alaskan roadie) who have advised us on the road conditions which is making me think twice.

 

Ignore knock sensor, unless it is confirmed by CEL.
For oil loss, investigate the oil through the PCV .. put a catch can before changing valve cover.
Check the lock actuator of the door that is not responding to door lock switch on the driver or front passenger side.
Water on passenger footwell is typically from A?C condensate that is not being drained out. As the vehicle ages, the heat exchanger clamshell joint stats failing.
Monitor coolant level and if you dont need to keep adding, just ignore.

Salim

 

needing to add coolant is concerning. If you have a bluetooth obd2 reader, you can monitor your coolant temp. If it rises above normal, you need to figure out if your cooling system is holding pressure. It could be something simple as a bad rad cap or as hidden as a pin hole leak in the radiator and/or components. If it down on power, also consider doing a block test..it would indicate whether or not you have developed a head gasket leak....burning coolant as a cause of a head gasket failure can throw o2 sensor code symptoms. Good luck.

 

3. Water on floor is from AC evaporator cloggage. Easy fix. On the passenger floorboard, left side lower console wall there are 2 access plugs. Remove them and the panel. Inside is evaporator. You'll see a rubber drain hose connected to evaporator, this drains out to bottom of car. Disconnect it and spray AC safe coil foam cleaner from Home Depot (6$) into evaporator connection. Fill the evap system. Reconnect drain hose, turn on AC full blast. You will see foam exiting car, along with tons of water and mildew clogged in your system. AC will run much cooler and better, no odors. 6$ fix, Lexus charges 200$ for.

 

As usual you guys are awesome.

thx. for the pointers. i will be checking the AC today.

 

Take pics and please post.

Salim

 

After much deliberation we decided to upgrade and picked up a 2007 RX350 with 160km. (the 2001 RX300 has been transferred to a another owner.) i will start another thread in the appropriate section for the new vehicle.

thanks to all who assisted me with the 2001 RX300, from my experience these are well built, reliable vehicles.