Haha I was actually just thinking of trying something like that today.
Wonder if I can modify the lines of the headlight sprays I never use to spray water on the Rad instead for a temporary fix
Glad to hear the truck has been pretty well maintained with a lot of the running gear maintenance being done.
Just an FYI, the newest 70 series we can get here in Canada looks the same as the vintage you have. So basically you can buy the heavy duty version (HZJ77) or a light duty version (LJ78 or KZJ78). The light duty ones are worth about $5k-15k depending on condition and if they're an LJ78 or KZJ78. The heavy duty ones are about $20k-30k. So quite a big difference. Main reason for the price difference is the engine - no one really wants a 2LTE.
The rounded landcruisers you're talking about are probably the 80 series and 100 series. Both of those are excellent trucks. They may look similar to a 4Runner, but they're not. They're more similar to a Tundra or Sequoia. Lots of power, and no under powered overheating engine issues. Good ones again cost more than an LJ78. Usually in the $15k-30k region.
So it really depends on what you want to use the vehicle for, and what your budget is. Personally I like my LJ78 as it fits down narrower trails while 4x4ing, and the diesel gets pretty good fuel economy (but so do diesel 80s and 100s I suppose). I like the square practical design. Besides the engine, they're pretty bullet proof. Solid front axle is nice (100s are independent front suspension).
Ok, back to your overheating problems:
First thing you need to get to the bottom of is why your coolant reservoir is overflowing. Even if your engine is running quite hot, the reservoir should not overflow unless something else is up (something displacing coolant in the system). I really recommend not driving it much until you get to the bottom of this. If the head is cracked the coolant can do quite a bit of damage to the bottom end of your engine also. The coolant can rust the cylinder bores when the motor sits, and it also pits the top of the cylinders really badly when it is exposed to burning diesel. Basically it'll cause you to loose compression and get blow-by. Low compression in a diesel sucks.
Look at all your rad hoses, turbo cooling hoses, t-stat housing, water pump (timing cover bottom), oil cooler housing, radiator end tanks and core etc. to see if you can find a leak. Lay under the truck and see if you can find any coolant dripping down anywhere. You'll smell it too when the motor is running. Replace the rad cap as soon as you can; I believe it crosses to lots of other Toyotas (I can look into it for you if you want). It would be good just to remove it from the equation.
The coolant under the hood cover might be spraying from your reservoir somewhere when your system gets highly pressurised.... It's not likely to be a normal coolant leak.
If there is no coolant leak, I'm afraid your system may be getting pressurised from combustion gasses.
Anyhow, couple things to check for:
When the engine is cold (and off) remove the rad cap and look inside the filler hole. Is there coolant, or is it full of air? Squish the upper rad hose, is it full of air or coolant?
When you start the engine and it's running rough, smell the exhaust. Does it smell like coolant? Any white smoke? Feel the upper radiator hose, does it get super hard really quick? This is a sign of combustion gasses pressurising the system.
When the engine is running, carefully remove the coolant reservoir lid, but leave the 'straw' in the coolant in the reservoir. Leave the lid to the side so you can look in. Watch carefully. Do you see bubbles coming out from the end? The coolant may be hot, so BE CAREFUL not to burn yourself. Do this check when the motor has just started. Also do a check when you've run a hill and the engine is getting hot. Again, be very cautious!
I can teach you how to service your existing fan hub. All you need is some RC car silicone gear oil. A couple little 10,000cst bottles will be more than enough. As long as the oil has not been leaking out and the front spring is intact, the hub is still fine. New oil makes a huge difference.
