+1 on replacing the fan clutch, trust me, you'll thank yourself, and here's why. I bought my 01 back in 2013 and during warmer months when I would run my A/C while idling or sitting in heavy traffic, my coolant temps would rise above normal operating temperature. Took me 8 and yes literally 8 years to figure out that the fan clutch was the problem. Another user on here (Street Creeper?) had mentioned that he had the same issue and resolved it by replacing his fan clutch. So I replaced mine with Aisin p/n FCT-013 and never had the issue again. I can now run my A/C full blast in 3 figure temperatures with no issues. All I'll add is to be careful when removing the 4 nuts that hold it in place, they can be easily rounded. They're like $80-$90 and I would do it all over again if I had to.

Very good thought on the fan clutch. As long as the thermostat is good and the radiator wasn't oxidizing. If those 2 things check out then the fan clutch is definitely a high possibility of being bad.

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That's good to know! Thank you! I'll put it on my list. Did you perform any testing on the fan clutch before removal?

To be honest, I didn't, but it was definitely bad. Like there was no question about it. I'll see if I can upload a photo on here to show you what the old one looked like. The coil in the middle of it was all burnt looking and just gross, but I don't know if that has anything to do with the actual performance of it. Standby for photo...

Old vs. New. Let me know if you want me to makes these smaller so as to not junk up your build thread.

How I test mine is when the engine starts cold it will spin for a little while then stop. You can also feel slight resistance when Turing them. My area doesn't get really hot. So mine and probably bad and I just don't notice..

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The one difference I noticed was that when shutting off a hot engine, the fan kept rotating for a few seconds with the old clutch, but stopped instantly with the new clutch. That would suggest that the new clutch was more firmly "coupled" to the pulley when hot, which seems like a good thing (less slippage).

I will check mine to see if they spin ot stop instantly when hot..

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5/20/2022 203149 miles
-Replaced front rotors (Bosch 50011224 $130) and front pads (Bosch BC611 $45) and new slide pins (Dorman HW14108 x2 $14)
-Replaced fuel filter 23300-62030 $60
-Changed engine oil $FREE
-Replaced oil fill cap gasket 90430-37140 $4

5/21/2022 203165 miles
-Flushed cooling system x3 with distilled water $10
-Replaced thermostat 9091603075 and thermostat gasket 1632562010 $32
-Replaced heater water valve 87240-35070 $35
-Replaced radiator Koyo VH010665N and radiator cap Koyo SK-C13 $420
-Filled cooling system with Toyota red coolant 00272-1LLAC and distilled water $70
-Removed and cleaned radiator overflow bottle $FREE

I started off draining the old green coolant out as best as I could, removing the thermostat (jiggle valve was at 12 o clock as I suspected by my higher temps) and then reinstalling without the thermostat. Switched front and rear heaters to heat, filled the cooling system with distilled water using my Lisle spill free funnel to help get air bubbles out, let it run for a few minutes, turned it off and drained the cooling system. Repeated that for a total of 3 flushes.

Replaced the radiator and discovered that all of the body holes for bolting the radiator in do not line up. Took a dremel and a couple bur bits to elongate the mounting holes. I didn't have any paint so I coated the bare metal with grease to prevent rust. I also discovered that my harbor freight right angle grinder head doesn't spin true and will explode a bit. That was fun... Luckily I have a dewalt right angle grinder as well. Just had to swap the bits out. Very disappointed that all the mounting holes needed to be elongated for the very expensive Koyo radiator.

Installed the new thermostat and gasket. Replaced the heater valve. I discovered when I went to fill the Koyo radiator that none of the Lisle spill free funnel attachments work with the filler neck so I cut a transmission funnel down to size to fit in the hole. That didn't work very well and the system wouldn't burp allowing me to put any more than 3 quarts in the radiator so I pulled the upper radiator hose and poured it down the hose until it came out the radiator. Reassembled and elevated the front end with the lift and ran it to get some air bubbles out. It didn't burp much which was suspicious so I have an extra gallon of coolant with me to top off after it cools. I parked it on a gnarly incline yesterday and topped off the radiator one last time. I've been seeing much cooler temps but haven't had the chance to tow anything again. Highest I've seen so far after the repairs is 190*F which is where my last 4Runner would go to.

EDIT: I'm fairly certain that I still had an OEM radiator as there were no transmission cooler fittings like 16410-AZ011 has which is what Toyota shows for manual and automatic 3rd gens. I guess Toyota figured it was easier to stock one radiator for all of them rather than have a separate part number for radiators without the transmission cooler for manuals.

I'm about to do similar, replacing the heater valve and removing the rear heater connection, and potentially the core

I'm also switching fronted to green and will use Blue Devil radiator flush with distilled water and new upper and lower hoses.

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I considered doing the heater core, but that would start a cascading repair avalanche. I would want to replace the evaporator as well which would lead to the condenser, drier, compressor, etc. The heat works great now so I'll postpone that until it either leaks or the ac gets a rebuild.

Removing the rear heater circuit (fluid) is pretty simple. I'll start there.

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I misread that lol I thought you meant the main heater core. I like my rear heater but to each their own

I'll add another +1. I had the same issue where engine temps would rise into the 200's idling with AC on in hot temps. Replaced my fan clutch and haven't had a issue since.