Hi all,
I am new at forum, I have 2008 rx400h with 101k miles on it, today I realized that coolant in inventor reservoir is boiling, it happened one time though, I parked my car, opened hood to check engine oil level then I realized that reservoir on driver side is boiling, first I thought it was gas engine reservoir, called my mechanic told him that coolant is boiling, first he said it sounds like head gasket issue, then a little research I found out that boiling coolant is at inventor reservoir, I dont believe it is related to gas engine coolant, any idea?

 

There is a electric cooling pump for the inverter. It may have failed and the coolant isn't being circulated. It is located on the drivers side down on the frame inside the engine compartment. Has two rubber hoses attached to it with an electric connector for power.

 

Thank you for quick reply,
Is it necessary to change electric cooling pump? Would it cause any major issue if I continue to drive like this? I see that part is about $300 :/

 

Have you confirmed that the coolant is 200+ degrees with a thermometer? The hybrid coolant generally stays much cooler than regular coolant. The electric pump causes some turbulence in the reservoir so that may be what you are seeing. The people that had failed pumps got a hybrid system warning telling them there was an issue. Hopefully you don't have an issue.

 

No, I haven't.
Only diagnose I have so so far is to touch water reservoir with my hand while it was boiling and it was very cool though, coolant did not feel hot or warm at all.

 

As for the pump failing yes you do get codes. I had mine fail, and the system basically shut down after awhile. I cant say I have seen the bubbling in the reservoir, but I will check when I get a chance. And yes if the pump failed it will put the car in limp mode.