Hi, RX Members!

I have a peculiar cooling system on my 2006 RX330.

Here are the vehicle specifics:
- 2006
- RX330
- 156k Miles
- Canada Built
- No tow package, but has transmission cooler built into radiator
- All maintenance up to date
- No CEL
- No Coolant leakage/seepage/residue after radiator replacement

Context
Last week my wife was driving approx 80 miles, then all of a sudden the A/C turned warm. My wife pulling into a parking lot, turned the engine off, then 'boom', steam poured out and coolant everywhere! After she had the vehicle towed home, I inspected the vehicle and noticed there was an 8" crack/opening in the plastic portion of the radiator on the passenger side of the vehicle.

Fast forward this weekend, I replaced the the radiator with an Lexus/Toyota OEM unit along with upper and lower radiator hoses. Filled it up with nearly 2 gallons of 'pink' Lexus/Toyota coolant; spent 20 minutes burping the system, and all appeared good. Went to take it for a drive and noticed the temp gauge climbing to the 4th tick mark and proceeded to turn the a/c off, temperature balanced out, then temperature began to rise while stopped/idling.

In addition, both cooling and a/c fan are operational and come on simultaneously/independently; system overflow tank in between low and full; spent 10 minutes burping the system with no change in coolant level.

My thoughts
- Possible thermostat malfunction? Coolant is passing through both top and bottom hoses, with each being warm/hot to the touch...
- Radiator Fan Module Going Bad? The fans are engaging/disengaging when a/c compressor kicks on...
- Coolant Temperature Sensor? The coolant dash gauge displays the fluctuating temp...

I'm at a total loss...so thought others might have experienced similar and get insight from those who have solved...

Looking forward to any and all thoughts!

 

I haven't experienced this myself but I'd say change the T-stat. Even if it isn't the cause, if you're on the original it's time. OEM only don't bother with cheap aftermarkets.

But I have heard the fan module as an issue on a few different Lexus' so consider that.

 

When I first purchased my RX330 I noticed the temperature gauge was fluctuating from normal to hot to notice I have a small leak at the very top of the radiator, a small patch of dried pink fluid.
I have the Transmission Cooler & Heavy Duty Radiator (yea, right) option. It took more than 1 gallon of Toyota coolant & more than 10 minutes to fill via burping. Just a thought, perhaps some more coolant required. The Manual states 10.1 Quarts which equals to 2.5 Gallons with the Towing Package.

 

Gone are the good old days when some would wait for the radiator to get real hot & crack an egg into it, radiator leak? problem solved, 2 cents for an egg.

 

Replacing the thermostat is a good idea, but it might not solve the problem because your hoses are warm/hot. That suggests the 'stat is open and hot coolant is reaching the radiator.
What is coolant capacity on your RX? If your change out was for full capacity, it suggests no major clog.
Is the lower hose less hot than the upper hose? The coolant at the lower hose should be cooler because it has passed through the radiator.

Here's a suggestion: has your water pump ever been changed?

 

I would start with going back and making sure system has no air. 3.5l has a bleeder valve on top of engine left side, 3.3 should have one too so find it and unscrew the center partially with RX running and look to see if any air comes out. Radiator has a valve too. If both hoses are hot and fan runs, typically thermostat is working. Could be water pump or any other part of cooling system that's compromised and/or letting air into system. Inspect your engine, particularly water pump for signs of coolant.

 

Many thanks to those who have read my thread and provided insight!

Next steps for me are to take it to a vetted mechanic who has more working knowledge of cooling systems...I'll report back once I know more!

 

Update:

https://www.clublexus.com/forums/rx-...-wanted-2.html

Post #23 appears to have solved my vehicles overheating woes.

Mechanic mentioned the radiator cooling fan for the a/c required a tap/nudge to move as it was intermittently activating.

Hope this helps other users in the future!

 

Good resolution. Thermostat or the cooling fan.

 

The model just sucks that's all there is to it and Lexus doesn't care they just claim total disregard to our issue with this rx model. I also found out another issue that these cars. Seems that when my car started overheating, I thought that once again I was gonna have to replace the radiator and spent a month babying it cause I didn't have the money to do it again it costs over $550 to do each time and that's not at a dealership I heard it's over a 1,000 at dealership. They don't use original manufactured parts either according to my source, at least not for that anyways. Turns out that what's really happened to mine at least this time is that I may have a possible air leak from the head gasket and the antifreeze is seeping into the engine burning off and going out the tail pipe, that's what my radiator specialist told me. I also found out that Subaru has this problem too with some of their models.