I looked the jiggle valve up on google, I swear the thermostat was like molded into the housing and didn't spin within the plastic housing, so it would be in the correct orientation when installed but now I'm wondering.

 

Actually that was my bad...the 350 comes with the thermostat as part of the housing, so really you can't install it wrong.
The 4 cylinder turbo model has the conventional thermostat that is a seperate piece from the housing.

Back to the drawing board.

 

Maybe try bleeding it again to be sure all the air it out.

Leave the car on level ground and remove the radiator cap (with the engine cold).
The coolant should be full right to the cap and the reservoir at full. If either are low top them up.
Start the car up and turn the heat on Face at full hot, fan speed Low.
When you start to feel heat out the vents, turn the temp to max cold...leave the Face and fan speed the same.
If the coolant gets low in the rad cap opening, top it up as you go along.
Ideally the fans should come on at some point (might take a while) and you will likely notice the level drop...at that point top it up and throw the cap back on.
Let is run for a few more minutes and shut it off.
Confirm the reservoir is still Full...top up if necessary.

Let the engine cool right down and recheck the reservoir level again...only the reservoir...top up if necessary to Full.

Take it for a drive and see if it still has the same issue.
Obviously this entire process will take some time.

 

Thanks for sharing!

 

No dice bro. Tried that, the fans wouldn't come on after almost 20 minutes without me revving it a few times to 2,000 rpms. Once they came on it cycled the coolant and the lower hose got hot. Coolant level didn't change, no real bubbles and I squeezed both hoses a bunch of times.

I shut it off and let the coolant in the radiator settle back down. Took it out and it was fine until I really got on it, got up to about 3/4 then went back to under half after running the heater for not even 2 minutes.

I flushed the radiator, no debris or sediment came out and the water came out the bottom just as fast as I poured it in the top

At this point I'm just about convinced it's the water pump internally, impeller or is slipping under hard acceleration. I'm going to hit up a bunch of shops on replacement cost, if it's $700 or more I might try to tackle it myself. There's a couple good youtube videos on it, just don't want to take that much stuff off it seems involved but maybe I'm over thinking it. Sucks man but almost 200k on one pump I guess I can't be that mad. Now I'm wondering if I should do the alternator too to be safe.

 

If the rad fans came on and the bottom hose got hot then that confirms the thermostat opened.
You said you didn't see any bubbles, but did you see the coolant rushing past the opening (like a running stream/river)? If yes, that means the waterpump was circulating the coolant through the system. If no, then that's an issue.

Let's just say for the sake of argument that the belt was slipping under load and not turning the waterpumnp fast enough...then it's not a waterpump issue, it's a belt/belt tensioner issue...so changing the waterpump won't fix anything...you'd be looking to replace the belt and tensioner.
Let's assume the answer to the question above was yes (you did see the coolant rushing by the rad cap opening), then the impellor on the waterpump is fine...cause if it broke off, no coolant would circulate and the car would pretty much overheat in less than 25 minutes of idling...forget about driving, the gauge would be pegged at the top. Plus you'd be the first ever on here to have a waterpump impellor break off...I can't imagine you're that lucky.

It's good you flushed the rad and confirm flow was just as fast going in as out.
Maybe you could try flushing the engine side of the cooling system...but that involves taking the thermostat out again.

It sounds like you've done all the right things so far to try and resolve this...just missing something.

 

I didn't run it without a funnel in the top, didn't want coolant everywhere, the other issue was it wouldn't get hot enough to open the thermostat with the cap off and just idling. I measured the coolant after 20 minutes in the funnel it was 180F. I had to rev it over 2,000 rpms a few times to get the fans to come on and thermostat to open but I should try it without the funnel in to check... I ordered a new radiator cap from Longo Lexus, don't think that's going to matter though cause the original one looks new, rubber seems fine and pliable, depresses fine. I'm lost here.

 

ran it with the cap off, looked like a weak clockwise whirlpool. Once temp hit about 205F the fans came on and the thermostat opened, it looked more like a river/whirlpool after that. I'm wondering if the original thermostat went bad, and the replacement is crap because it's a duralast, the date on it is 6/2018...I looked on rockauto and the aisin O.E one is supposed to open at 180F. I ordered the aisin from rockauto, guess I'll switch it again and see. I did boil the original thermostat and it opened about 1/4 of an inch, the spring wouldn't collapse any more than that so confirmed the original was a big issue, if not THE issue. This duralast is probably trash, I'm reading issues from other boards with duralast thermostats not opening until 205-210.

 

On the original thermostat there should be a stamp on the neck that states 180...letting you know the opening temp.
I wonder if the Duralast one has a similar stamping. I think this was the first mention of the replacement thermostat not being an OEM one.

 

the side of the housing says 82C, the old googles says that is 179.6F, so 180. (this is the original one I pulled)



I put it in a pot of water to see how far it would open and at what temp







at 200 it was what looked to me to be barely open



this is at boiling temp, i took it out and immediately took a photo...from the photos online I have seen, that large spring should collapse much farther than that, the opening here doesn't seem large enough to allow efficient circulation which would explain why it would get 3/4 up the gauge then go back to normal running the heater on full blast, it was allowing SOME, just enough to not completely overheat. I'm reading that these duralast ones aren't opening until a little over 200. If Lexus designed them to open at 180, they did that for a reason.

I could see how the duralast one not opening until at least 200 would mimic these same symptoms, the thermostat opens when the coolant is already too hot per manufacturer spec, by the time it circulates to cool it gets a little below 200 and closes again...never getting down to the 180 lexus calls for before closing, thus not allowing the coolant to get cool enough. I'm not super knowledgeable here but that's how it makes sense in my mind. This thermostat looks partially open to me, what do you think?






EDIT: tried to shove a screwdriver in the opening when it was "open" to pry it open and see if it could open more, it did, then broke lol. I guess I could install this housing without a thermostat and see if it repeats the issue while waiting on the aisin one to come next week, not sure what a lack of a thermostat would do to emissions components or other things though, might get the "open loop" code

 

I think your assessment of the old and new thermostat are spot on.
If the new thermostat is opening later than intended then it will essentially cause the same issue.
I'm surprised the thermostat stamp was in Celsius...I just assumed it would be Fahrenheit...but I think I forget to account for where the car is built...not where it landed.

Running without the thermostat will definitely stop the issue, and in a climate where the ambient temp is hot, it shouldn't pose too much of a problem.
In a colder climate I could see it being an issue as the motor would struggle to retain heat.

 

central cali, its going to be 110F soon lol.

check this out, I pulled the duralast thermostat, it's actually made by "motorad" whoever that is. I threw it in the same pot, 180F nothing, 190F nothing, it didn't START to open until 200F and didn't open wider until boiling. I don't even know if it was fully open cause water only gets so hot. I installed the old housing with no thermostat and I'm going to see how that runs while I return this POS one to autozone

 

Ran with no thermostat, same thing, WHAT THE ??? I even took the slack off the serpentine belt and tried to see if there was any play with the water pump pulley, nothing, solid as can be. This has to be the water pump or coolant temp sensor, engine temp sensor whatever it is right? I can recreate this issue much quicker by turning the AC on full blast while driving at 4k to 6k RPMs for a couple minutes...that might seem harsh but really it shouldn't get 3/4 on the gauge from just that, something is up.

I'm going to order one of those no-spill funnels, install the new oem thermostat and run it with the funnel in for 45 minutes...if that doesn't do it then there's literally nothing else but the pump, or some temp sensor.

 

I would have gone with an OEM Toyota/Lexus thermostat or even a Denso blue box (first time fit) over a Duralast. I highly doubt the Duralast thermostat will last as long as what you just replaced.

 

I was in a pinch, I ordered the aisin one. I also ordered the aisin water pump, guess I will tackle it since it has 192,000 miles it's probably a ticking timebomb anyways. Also ordered a spill proof funnel to bleed the air. I had a shop quote me $1,800 to change the water pump, not even a dealer, I just watched this asian dude do it on youtube it doesn't seem that hard just messy