Maybe a partially blocked rad , inside or out . Play in the mud a lot?

Try to avoid it at all costs.. Mud is no friend of mine! I'm old enough to have learned that the hard way through high school lol.

I'm experiencing similar issues. Did this ever get solved?

How to resurrect this old thread???

I would start with changing the thermostat (giggle down) and consider replacing the Radiator good insurance for pinkmilk shake.

@JWaldz Im interested too, my 98 3RZ auto has been getting higher temps lately (200+ on occasion). I've been attributing it to the warming ambient temps outdoors, or heat sink effect (shut down at operating temp, started again within 5 mins and temps are high), but I'm curious if the thermo will cool it down a bit. Mine is most likely stock.

I replaced leaky lines to rear heater, radiator and hoses, water pump and gasket, everything but the thermostat (in the parts box, just got waylaid). I'm guessing that is what's going on with mine.

I had issues with higher than normal temps after having a mechanic do a timing belt change, which includes water pump and thermostat as preventive maintenance.

Before the timing belt change the temp ran about 190F (88C) with a Scan Gauge II device, 'cause the temp meter isn't working, which is normal for a 2000 4runner. After the service the temp would climb to the mid to high 190's, and on an incline would get even higher. Living in WV there aren't many flat roads so I was constantly driving with OD off, and on many occasions having to pull the shifter into 2nd just to keep the temps in check.

Complained to the shop about the higher then normal temps, but they dismissed it, saying anything under 200 wasn't considered running hot. He was used to Chevy's, which run about 215F. They did change the thermostat, but no change.

Finally had enough, so I removed the thermostat completely and took it on a test run on my favorite 8 mile uphill stretch, and temps never climbed above 178F.
Ordered a OEM thermostat from Amazon and when I got it I noticed a huge different between that and the generic one. It is larger and beefier, and the package said high flow thermostat.

Installed it and problem solved.

Glad it helped but your mechanic is right. I've climbed as high as 230 degrees briefly in mine (don't ask) with no ill effects. On that same engine, I'd see 200's regularly in summer heat with A/C on. The coolant is under pressure and has a boiling point of over 235 degrees depending on coolant mixture. 190's isn't really that much at all. GM's do perch precariously hot though since it only takes a bit hotter temps to start doing damage and doesn't give much time to react.

Getting up into the low 200's is a non issue.

@chewie @Crowcifier6

I think it was beginning stages of headgasket failure. Not to mention my radiator developed a leak that was untraceable as it wasn't enough to hit the ground. Throughout the next year or so the engine developed other problems, the headgasket finally went, and the engine was toast. I will say, while yes low 200s certainly isn't an issue, per say, but consistent temps in that range should be addressed. It could have long term effects. The engine I put in along with a new radiator, I hardly ever see 190, and I drive it every day.

I did timing belt/water pump job back in March which included Oem thermostat. Unaware of any issues until 2 months later-
With higher temps outside, I was idling in a parking lot for about 15-20 mins after driving 20 mi on interstate. As I was leaving I noticed the needle was about 3/4 up and thought it needed air so I got moving and it settled down.
At this time I began monitoring the coolant temp via Fixd reader and app which was showing me an average operating temp of 204 with readings as high as 216 in stop and go and up hills.
Research led to the fan clutch test, which failed. I replaced, I also flushed out green coolant and switched to Toyota red.
Back on the road this week, the highest temp I’ve seen is 208 and averaging 199-204. Better but not satisfied as I believe that’s too hot for regular driving here in the low country and it’s not really even hot out yet. I’ll likely see another intermittent overheating episode with the right combo if nothing is done.
I’ve read about the jiggle valve NEEDING to be a six o’clock and fixing similar symptoms. Also read about testing the ECT sensor which may be giving a false temp, and the possibility of a faulty thermostat which apparently happens a lot.
I’ve ordered a new OEM thermostat and will test it before pulling the current. Will also check current thermo for jiggle valve position and, if correct, will test that one for opening at correct temperature.

Thanks @JWaldz . Motivation to try and bring my temps down. I saw 216F on my Scangauge II yesterday after driving around mid day. Outdoor temp was a mild 75F, quick run into the store (engine only off for <5mins.)

The heat sink effect, where the engine actually gets hotter after shutting down before cooling is where I see the highest temps, driving usually not over 197F.

Anyone have the 4 cylinder 3RZFE? Wondering how much coolant I'll lose just replacing the thermo...

I tested two new Toyota thermostats, trying to see when they open exactly and at what temperature. Then pulled my existing for a third try.

**Jiggle valve found at 12 oclock**

Minor difference in one of the 3 which seemed to really open at 185°F while the others at 187-188°F. They all seemed to crack open at 183 and then would let out a little air bubble a couple degrees later which I felt was truly open. Anyways, it's pretty hard to tell any real details of the stove test other than if something were really wrong or faulty.
I did put in the "better" thermo but installed with JIGGLE VALVE at 6 O'CLOCK position and it made all the difference!

80+ degrees outside, I took a test drive over a bridge with a long 2.5 mile grade one way then back with a shorter but steeper grade the other direction. A/C on the whole time with a good load on the engine, the temp didn't go above 194°F giving me at least 10° cooler running temp.
I'm convinced the jiggle valve had everything to do with my issue of low 200° temps.
Thanks to this thread and others on this site, I shouldn't overheat randomly and probably helping preserve the life of my head gasket and ultimately the engine.

Hope this helps someone else!
****SCAN your temps in real time cause your cluster temp gauge won't tell you there is a potential problem!!!