06 RX330, 195k, timing belt was done at 100k, car was meticulously serviced at a Lexus dealer all it's life.
I got it with 190k, no problems, planning to do t-belt and all associated stuff... and today it starts overheating to about 3/4 hot.
I shut it off and notice the reservoir is dry, weird. I add Toyota pink coolant to the full mark and start it back up. Heat coming out is lukewarm, but I get on it a little and heat starts coming out nice and hot, but the needle starts creeping up again slowly. I'm watching the temp in the Torque app, and it's climbing like 1º every ~15 seconds maybe. I pull over as it reaches 3/4 again, and notice the coolant has gone down some in the reservoir, and it's boiling like hell.
Please tell me it's just air in the system and not a bad head gasket

I babied it home 5 minutes with the heat on full and parked it. It's never had a coolant leak before this, except likely behind the thermostat where it leaks onto the knock sensors (CEL is randomly on/off for those, no other codes).
Obviously I'm going to burp the system when I have time, but idk. I suppose I don't know what kind of reply I'm looking for here... but just kind of frustrated as my last car got a bad head gasket probably 1k miles after I had the whole timing job done, ****ty luck.

 

I'm sorry friend, I really hope it's not a head gasket.

If your thermostat is stuck closed it can overheat quickly.

Add a bad radiator cap and it can maybe backflow the hot coolant into reservoir.

Maybe wishful thinking, just ideas based on your symptoms that are not head gasket related.

Hoping for your success

 

You could luck out and find it's as simple as air in the system but not likely as it is a closed system so how did it get there? Could be an old dried out radiator cap as they do degrade over time (I'd replace it as a maintenance item anyway). My guess is at those miles it's the radiator itself... take a very good look at the sides, both front and back look for any dried pink color of it is there it's time to replace it. Good time to closely inspect the houses as well. As said probably a good time to change out you thermostat as a maintenance item. Radiators are known to go at those miles.

I just did my radiator at 170k miles as I could see some pink on driver's side front and rear once I took it out I could clearly see it was leaking more than I thought... Only replace it with an OEM or Koyorad never a cheaper brand. It is not a tough job to replace it at all.

I doubt it's your head gasket unless it went over danger temp. Pull the dipstick, is the oil clean or milky? Is your exhaust clean and odorless or is there any steam and does it have a sweet smell to it?

 

Before spending a lot of time trying to figure out what might be causing the problem, tackle the dreaded head gasket first. You can buy a test kit or go to your mechanic and have them test for combustion gasses in the coolant. Then at least you'll know. Bob

 

Assume the plastic radiator shoulder is not split. It is a classic on the 400 and I assume similar on the 330. I had this problem and the radiator emptied quite quickly. Radiator replaced problem solved

 

1. Thermostat (oem)
2. Knock sensors (oem cheapest I could find from an actual brick & mortar dealer was $139 each)
3. Knock sensor harnesses (ebay cheap)
4. Intake manifold gasket (oem)
5. Coolant temp sensor (oem)
6. Coolant bypass hose (oem)
7. PCV (oem)
???
Anything else?

 

I got to do this today... thermostat finally opened at 194º, upper hose was cold until well after reaching operating temp.
Pumped the test kit for a good minute and it stayed blue, hooray!
Took it by the exhaust and 3 pumps in it turned yellow, so I know it works.
Time to tackle that thermostat! I made a new thread with a shopping list, trying to get everything in there at once.

 

194 is not bad, but the thermostat could be sticking. You didn't mention the fan; I presume it is functioning ok. Another possibility is a plugged radiator. You would need an endoscope to view the internal drain passages. Generally, if you can see clear passages through the cap opening, you can infer the others are ok.

 

And certain it isn't a classic plastic hairline fracture rad leak from. No mayo in oil filler area?

 

Someone please correct me if I'm wrong but I think 190f is the spec for the thermostat.

However, if it sticks(even one time) can overheat and ruin the engine do to restriction of coolant flow.

I don't mess around, I put in an OEM thermostat when I first got my car just for preventative maintenance.

Only other thermostats and radiator caps I trust are ones made by Stant.

They've been around for ages and also made high end mechanic duty coolant system testing tools too.

 

I am thinking 180 but not 100% sure. I know my 07 Tacoma V6 is 180 and the average temps are 190-195 with Aisin thermostat. Before that one I had a Motorad 180 thermostat and the average range was 200-205. But, in both instances, the temp needle was always at the half point.

 

OE thermostat 90916-03129 *WAX 82-95

Gauge cluster is not real time or even the actual temperature it is fuzzy logic.

 

I did the thermostat yesterday, not nearly as bad as working on an Audi, that's for sure.
There was some kind of parts store thermostat in there, it had zero writing on it, couldn't even tell what kind it was, replaced with oem tstat (90916-A3003) and gasket (16325-62010)

Did a test drive today, and I left small wet spots every time I parked somewhere...

I flashlight around, and notice what Vincenze was talking about, it's leaking from the side plastic, under the sticker!
Unreal.
I'm going with a Koyo radiator, as I know they are better quality than OEM, and all aluminum, no plastic.

OEM on left

 

Koyo rad that is all aluminum? Where did you find that?

 

This^^^ As last yr, I had to replace mine & find no alloy radiator for this vehicle.....Its not a truck or muscle car.