2006 RX400h Overheating at Freeway Speeds

michellecat · August 2, 2016

This has only happened twice since I've owned the car and both times it was in the exact same spot 75 miles south of where I live on a hot summer day after going about an hour at freeway speed with the AC on. The first time i freaked out and rented a car (both times I was heading out of town for vacation). The second time I just pulled over to a gas station, waited twenty minutes until it cooled off and then went the rest of the trip (about 400 miles) with no problems as long as i didn't run the AC.

bought in 2013 with 36k miles

had to replace the cracked radiator about a year later it was leaking on garage floor but not causing any overheating issues

3 years later i am at 85k with no issues running the AC on 100 degree days as long as it's around town or a max of 50 miles from home.

It will be hard for a mechanic to recreate unless they spend two hours driving it out of town and back so i am wondering if anyone else has had this problem?

Also,

problems getting full heat in the winter, especially when the outside temp is about 40 degrees.

There is a strange sound (vent doors maybe?) that comes from just right of the stereo. Almost sounds like water boiling but it happens the minute i turn on the car and it's intermittent.

Thanks for you input!

TrevC · August 3, 2016

Hi Michelle,

It sounds like you have some air in the cooling system.

Two reasons, one...the engine overheating, and two...the heater not producing warm air.

If you have air in the system, this can lead to poor circulation of the coolant around the engine and heater matrix. The important question is how is the air getting into the system.

First place to start is the testing, or replacing the coolant pressure cap on the expansion tank to ensure that the system pressure is maintained, if this drops then the coolant boils off and leaves air in the system.

Secondly, look for traces of leaks in the system...usually a trail of coloured staining around hoses and joints. A pressure test of the system will reveal this.

Let us know how you get on with it

Regards Trevor