Hey all,
It’s been hot around here, was driving with A/C on the highway for a couple hours and noticed temp gauge climbing on my 2006 rx400h. Killed the AC and luckily got off highway before any warnings. Once off highway I was able to get home due to hybrid system taking over at slower speeds but temp gauge was all over the place as soon as engine would kick on. I think thermostat is to blame as heat wouldn’t work… I think that helps us eliminate the possibility of broken fan? Also, coolant hasn’t been changed during my ownership so there’s that.

Anyway, I know this is a challenging job- or at least more so than one would think when one thinks of thermostat replacement. I know you need to disconnect and remove inverter to get down to the thermostat… I’ve been looking around for some step by step instructions or a youtube video and found very little. I have done work with hybrid systems on Prius’s and know my way around the mechanics, don’t think this job is too far beyond me. Was wondering if anyone has access to some instructions/ a video they can find?

 

Hi pwinks!

My apologies but I don't have an RX400h but I do have the manual and will look up some stuff when I have time.
Someone correct me plz if I am wrong but I believe you can sneak that thermostat out of there without removin the inverter- almost positive from looking at the drawings.

If it's located in the same place on the 3MZFE engine as my RX330, here is the easy access way and should take only 10 minutes to find out.

Steps:
1) remove the air cleaner assembly
2) remove the lower air cleaner box
3) remove the battery
4) remove the lower battery tray

Sounds like a lot but it comes apart fast and easy and now you have room to work and SEE.
Next, take a flashlight and feel & look up in there.

Mine removed with a 3/8" ratchet and socket using a mid length(9" approx) extension if I remember and I was working kinda blind- limited visibily and more feel.
Let me know cuz if you can do it I will post up the info on the install- new Tstat has a jiggle valve that must be inserted properly or you will have hell trying to get all the air out.

 

Much more likely your radiator is leaking leading to not enough coolant, which will result in no cabin heat.

 

Sorry, I should have mentioned, levels in reservoir are good, radiator is filled to the top.