I have done some research on the site but have not seen anything that fits my problem.

1st: Guy before me swapped out the mechanical fan for 2 giant electric ones. they come on when they should and dealer swears they should work better than the stock fan.

2nd: I have replaced the T-stat with a 180 stat. [twice] just to make sure, Radiator is new

3rd: truck does not over heat under normal operating conditions unless I rev the engine high for a short while passing etc.

OVERHEATS WHEN: Problem occurs most when in 4x4 or 4 low and climbing hills etc. Anytime I am in 4x4 putting more than normal strain on the engine. The temps just rise and rise etc until the coolant overflow fills and then it just spits it out on the ground from the overflow.

This is where I am confused. From the look of the overflow, its meant to do that. there is no hose attachment etc to recirculate the coolant when the PSI changes. its just a spout that dumps on the ground?!?! Is this really normal?

Tranny and Transfer are normal temps, both rebuilt within the last year or so professionally.

Water Pump? [how do i test and what do i look for?] any suggestions are appreciated. [I jsut did the plenum a while back too and ignored the water pump like an idiot....]

 

Weep hole on underside of pump will leave green trail to see if it's bad. Air in the cooling system creates turbulance that keeps it from circulating smoothly. Top it off & burp it to be sure. Could also be build up of corrosion so a flush may help too. Any or all of these things can cause overheating, but my money says air in the cooling system. Search sticky for each of these for details galore.

 

do you have a shroud around your fans? I know you said they are aftermarket, but I have found that shrouds make a HUGE difference! Especially in this Florida heat!

 

inadequate cooling..... either you aren't getting enough flow, or, something is plugged up somewhere... The coolant overflow tank spewing is NOT a good sign...... It really shouldn't do that. The idea there is, as coolant expands, the excess goes into the bottle. When the engine cools, and the coolant contracts, it develops a bit of a vacuum in the radiator, and the radiator is supposed to suck it back in from the overflow bottle.

Test your radiator cap......

 

I have seen impellor on pump crack, this will cause lower than expected flow at higher rpm.. However since history of overheats, you may want to ck for Hc in the coolant which could indicate combustion in cooling system from head/gasket.. This will airate coolant system and thus the same result. Block tester's arent that expensive and "**** yellow" is a bad sign ..

 

What color is the truck in question?

 

Sounds like the Radiator cap and Tester is going to be the first check. I am fairly sure there isnt any air in the system. I burped it pretty good last time. If the tester doesn't work, time for a new water pump.

Truck is white
=]

 

WP maybe?

 

THats next on the list. Chem tester was perfect. the guys at the local autozone know me pretty well so they just threw one at me.

Bought a new radiator cap just in case. Its been idling for a few minutes and temps are still holding kinda hot. Never used to do that even at idle and there is small bits of something coming out of the coolant. Im going to flush the crap out of it then change the pump next i think. Its a pretty quick fix when you do not have a mechanical fan =p

 

Take pics.