I have been slowly losing coolant, yet no puddles are ever evident. I have replaced radiator, thermostat, top & bottom radiator hoses. After a few hundered miles of driving with a full radiator (burped & inspected 3X), the 4runner (1993 3.0, 4x4) will start running hot. Sometimes the needle on the gauge will start dancing from normal to far left and anywhere in between. Sometimes it just sticks to the futherst left of the gauge like it went to sleep!! Sometimes it starts creeping to the ever ominous "redzone".
I can acknowledge that I may need an new sending unit, but after letting the motor cool to cold, the radiator sucks down up to a gallon of mix depending on how much I have driven it. I have about ruled out the infamous HG (the motor has around 50K on it)...
What other components of the cooling system could be the cause??

 

that looks to be around the tcase or tranny... sure its water and not some type of oil... how is the condition of the exhuast? it could be a number of things.... might even be a freeze plug on the engine, but those pics look too far back for that... maybe an auto tranny cooler line?

 

That is the transfer case.

 

First you should definatly get a new sending unit!

Second that looks like it could be comin from the rear heater (which has two coolant lines running to it)

 

That would make sense, I traced the line from the bottom of the radiator back here and the leak is right under the rear heater...
What should I do??? Pull the center console??

 

the center councle is 4 srews should take about 30 seconds. then you can see if its leaking from the heater or a fitting, you can pull the heater very easily too.

 

I am trying to pull the console. I can move it freely about an inch vertically, but cannot comletely remove it from between the seats. Should I use the force??? Do I need to unhook something I am not seeing?

 

You have to disconnect the two rubber hoses that come up to the heater core from below. Likely cause of the leak is the rubber lines themselves, that's where mine started leaking.

 

Your pic is of the transfercase. The line that comes out the rear of it goes to a cooler for the fluid in it. Its a shared tranny fluid hydrolic controled unit.

Ive known people to have a radator that is starting to leak, but only under pressure, so because the fluid is underpressure(higher temp) as soon as it leaks it evaporates. leaving no drips or puddles. (like a seam on the radator is starting to fail)

The heater hoses at the rear are also suspect, Mine leaked at the rear, which dripped down the back of the hot block and evaporated. never really formed a puddle till the hose compleatly rotted off on the interstate...

 

There are no visible holes in the lines to the rear heater, but they are pretty corroded and soft and have a lot of buildup on them.

Where are these heater hoses you speak of??

 

Also check the j-tube at the rear of the engine, in front of the firewall. It's a tiny little hose, but it leaks sometimes, like any hose.
I'd also suspect the casting plugs mounted at the point where the engine meets the tranny...as in you can't see it without removing the tranny. There are 5 little brass casting plugs that can corrode and seap.

 

Where does the metal pipe go that the j-tube connects onto? I have leak in mine and I would like to try to replace it with a rubber hose, however I cannot see where it goes.

 

anyone know?

 

the ones that rotted out on me were on the rear of the motor, the water bypass outlet



see the http://personal.utulsa.edu/~nathan-b...68cylinder.pdf for the entire thing