Hey all!

My 2007 Lexus RX350 is having a problem. I haven't had it very long (about 1 month). Within 15 minutes of driving (the past two times I've had it out) the temperature gauge goes almost to the overheated mark (not quite overheated, no bells go off or anything) and then it will drop back down a bit (not all the way back to midline, but enough to look safe to drive). It will go up and down as I drive. It doesn't seem dependent upon engine or vehicle speed. There is no visible coolant leak, but the overflow tank was empty. I refilled the overflow and it is not pulling coolant to the radiator (a buddy tried taking the cap off and warming the engine and I'd guess around 2 cups boiled out. We refilled the reservoir, let the car idle for a bit, and the level in the reservoir has not dropped). I am replacing the thermostat and am debating replacing the ECT sensor while I'm doing that.

My question is, am I missing something? My experience with car repair is on old school/classic cars. I'm not used to sensors, computers, etc. So, I need to know if I'm overlooking something obvious. If it was a radiator or hose the gauge wouldn't drop back down and it should run rough or give some other indication that there's a problem. There hasn't been any odd odor, no signs of a leak under the car, etc.

 

Read this, post 9 about how to fill coolant, harder than it appears...

https://www.clublexus.com/forums/rx-...g-coolant.html

 

Happened in my wife's 08 RX350 a 3 years ago. Had to replaced both Coolant Temp Sensor and Thermostat. My mechanic went the cheap route and replaced it with a aftermarket Thermostat. Long story short, after replacements the RX350 still overheated, he had to do the job again with an OEM Thermostat. No problem ever since.

 

There's an air bleed screw on top of the engine. Loosen it and the air will purge. Do so until it trickles only coolant. Take off your engine cover and you'll find the bleed screw over on the passenger side of engine.

 

It's also worth noting to confirm both cooling fans are operational.

My non-technical observation through research and first hand experience is that the fan motor magnets could wear out and cause intermittent symptoms.

 

Definitely. It sounds like there's something failing to cause this issue. I wanted to mention the bleed screw as there's lots of comments in this forum about difficulty bleeding air off, but little mention of the bleed screw. Trapped air can cause issues as well.

 

Check radiator, check cooling fans, check for head gasket leak.

 

I drained and refilled my coolant and apparently I have air in the system from what I can gather by searching posts. My heater is not blowing hot air and I'm overheating. I have an 07 RX350 and took the engine cover off. I can't seem to locate the bleed screw. Where exactly is it and what does it look like? I also saw several postings about a bleeder valve on the radiator. I do see something on the top of the radiator on the passenger side that looks like the drain plug on the bottom of the radiator - is that it? Do I need to open both of these or only one to burp the system? And should I do that with the engine hot and should it be running when I open the valves?
Thanks.