I Was driving on the highway (65 ish) maybe a moment of aggressive acceleration in 4th but as I was cruising I noticed some splatter on the bottom left of the windshield and then saw the temp climbing.
I cranked the heat, temp went to normal and got off at next exit. When I was able to stop I saw some coolant dripping on driver's side, the overflow cap was off and I could see the upper hose was about half full.
I let it cool and it started and sounded normal.
Towed home, sat a few days and eventually pulled her in to the garage to start diagnosing. I did notice the fan kept spinning after I shut her down and it is easy to spin hot or cold.
My theory was that my aggressive driving (small pulley maybe 14 psi) pushed past the gasket and put pressure into the cooling system.

 

The fan spinning freely like that says fan clutch (fluid coupling to toyota) has gone bad in loud words. They're not the most expensive part in the world. Easy to replace, too. 4 nuts hold it to the pulley it runs on, and 4 hold the fan to it. It takes a little bit of weaseling it around to get the fan/clutch assy out from the shroud and so forth, but it's not super hard. None of the nuts are on super tight from the factory, either. They unscrew pretty easily. Both on the pulley, and on the fan both.
Even a long time radar tech, not a mechanic by any stretch, has been able to do it on his 99 4Runner, his 87 4Runner, and his 87 pickup. All several times. Well, only once so far on the 99. Big secret is that you need small hands to get to the nuts on the pulley. Thankfully, my lovely wife, who is a great mechanic, trained as a Airframes Mech by the Navy (her father), has small hands to fit in where my big, fat, mitts don't.

Even free-spinning, the fan is not allowing enough air to flow through the radiator to keep your truck properly cooled. The cooling system pressurized due to the lack of air flow, so it blew coolant out into the recovery tank, or overboard. Maybe some steam blew out of the radiator cap, and condensed on your windshield.

REPLACE the fan clutch. If you didn't overheat too badly, your head gasket should be fine. Check the cooling system carefully. All the hoses, the radiator, thermostat, and so forth. If it's OK, refill it properly with Toyota Red coolant and distilled water, and give it a try. Don't even think about running it long without the NEW fan clutch, though.

I wish you all the best! Keep us appraised on how it goes.
Pat☺

 

But since you have the head off...there's probably a lot you ought to do while you're in there. My truck is still young at 290,000 miles, so I haven't needed to get familiar with it. I know when I had the head off my 78, there's a lot that might as well be replaced while you're there. Obviously make sure the block and head are completely level, since it did very slightly overheat. Other people may have advice on whether to have the head rebuilt while it's off.

 

[QUOTE=83;52461453]But since you have the head off../QUOTE]
The head is not off!!!
I still haven't been able to do a leakdown test yet.
Those pictures are from an inspection camera.

 

Are you by any chance in the mountains? Two separate times, out in Colorado, my wife's '96 has boiled coolant going up mountain passes. Both times we initially assumed the worst, but it was just a failed pressure cap on the radiator both times (first the OEM cap that was 20 years old, then the cheap Autozone (the only place open when it failed the first time) cap failed a couple of years later. Bought another OEM and it's been good ever since. WIthout pressurization, plus some altitude, the boiling point eventually gets to the thermostat's temp setting, and it boils,. and when it does, it pushes a lot of coolant out.

Another option would be a failing thermostat that just let it spike too hot. Or a kinked rad hose? Or there's a slow leak and it just got a bit low, boiled, and then pushed a lot out at once.

And on my turbo Volvo (which was running 22 - 24 psi of boost) I had occasional issues with headgaskets. I was using MLS (multi layer steel) gaskets, due to the boost levels (which is what late model 5VZ's use, and if an earlier set was ever replaced (possibly under warranty), they may have used later gaskets) - but one of an MLS gasket's party tricks is to 'self heal'. Run a lot of boost, it will leak and push coolant out of the system, let up and the layers will fit back together and seal again, and you can drive hundred of miles like that (I've done it) with no issue... unless you get into boost again, at which point *WHOOSH* again. It's not like a conventional gasket failure that physically pushes the gasket out of the way to create a permanent leak. Just an 'occasional' leak under boost.

PS: It will really open your eyes when it pushes coolant at 70 mph, wets the rear tires, and the wheels start spinning and going sideways...

 

Ah, ok. I thought you had already torn into it. Well maybe you're in luck. Boiling coolant is common on some vehicles. Way back in 2001 I had a Forest Service seasonal job and the Jeep Cherokee my supervisor drove would overhead on dirt roads all the time, and the coolant would be steaming. N

Not normal on Toyota though...But yeah, hopefully you've got something simpler than a head gasket going on.

 

I do not live in the mountains, although I do travel to slight elevation regularly. This happened at sea level. When I lived in Cali I spent a ton of time in Tahoe and never overheated climbing the Sierras.
I Was able to perform my leakdown and it all seems to be great? Oddly both sides measured the same
I tested at 90psi
2- 90psi/84 psi 7%
4- 90psi/80 psi 11%
6- 90psi/86 psi 4%
1- 90psi/84 psi 7%
3- 90psi/80 psi 11%
5- 90psi/86 psi 4%

Maybe it was just the fan clutch? Could I boil the coolant driving 70mph on the highway on a cool day if the clutch is malfunctioning?

Now I'm not too sure where to go from here. I'll replace the fan clutch, water pump and thermostat. Do I replace the radiator just because? My timing belt was done 100k ago, do I replace that now that things will be apart?

 

I bet it was the fan clutch Almost positive. Almost I say/ Pretty confident, though.

Positively replace the fan clutch. Replace the water pump if the last time it was changed was when the timing belt was changed 100K ago. Check this kit! Never hurts to put a new Thermostat in. I do mine every few years, when I flush out the system and put new fluid in. You can check the old thermostat in a pan of water on the stove. Have a thermometer able to read well above 212° F (100C). Warm the water to boiling and watch the thermometer to see where the Tstat opens. Don't let you wife see you! She's liable to have kittens over you boiling up car parts in HER pans. If she does, tell her you're making dinner for her, so she can sit and relax. Wash the pan well afterwards. Should be about 180°F. If it's good, save it for Justin. You know the guy. Justin Case A new thermostat is a small, and inexpensive, bit of insurance against unexpected failure.
Believe it or not, running without the thermostat installed, actually makes it run hotter. The thermostat restricts the water flow a little, slowing it down, so it spends more time in the radiator, allowing better cooling.

You probably should replace the belt while you have things apart. You can get a kit that has the belt, gaskets, little bits and pieces you need, and so on. I believe some of the timing belt kits include the water pump, so check out what kit you are going to buy before you purchase a separate water pump.

Have fun!
Pat☺

 

if you’re doing a water pump, replace the timing belt and tensioner because you already have 95% of the work done. Replacing the road is up to you based on the condition of your current one.

ABSOLUTELY will a failed fan clutch allow your vehicle (especially your forced induction) to overheat at highway speeds. Aerodynamics push the air either up and over or down and under, not thru the vehicle.

 

One thing that was not mentioned was the radiator … I did the Taurus electric fan replacement so I don't have the clutch fan at all. I normally have temps anywhere from 181-192 and my electric doesn't even kick on till it hits 196. Cool air going through the radiator at 55 mph seems to be fine. I have a fairly new radiator and use the Toyota red coolant. Has your radiator ever been replaced, flushed or other maintenance been performed on the radiator? If it is a bit plugged or has any restricted ports reducing coolant flow could also be a potential issue. Something to consider. You could even do the electric fan replacement! You have pretty much everything ready to do it! Hope you do find the issue. Best of wrenching on this one

 

I started tearing her apart today. My aim is to do the timing belt, front seals, water pump, thermostat, radiator....
I installed one of those coolant filters in the upper hose and found a small amount of metallic debris with a curly-q. Not sure if that has been there forever or maybe part of the water pump? Time will tell (maybe)

 

Finally got everything done and back together today. Runs just as she did before. I killed my ac idler by degreasing the front frame / engine, my dipstick o ring was mia. I never found anything exciting, the water pump looked great and I could maybe convince that it had had a little play in the shaft...
I hooked up my obd scanner and noticed ect 190-203 on my drive with hills and a little boost on the highway. I think it is a little high from what I have read? Maybe not with a supercharger?