COOLING SYSTEM

OK HERES THE PROBEM....RADIATOR OVER FLOW FILLS UP WITH COOLANT BUT DOESNT RETURN INTO ENGINE...

I CHANGED CAP, RADIATOR, AND HOSES...IS THERE ANY OTHERS THINGS THAT I OVER LOOKED...AND I RUNNING STRAIGHT FLOW NO THERMOSTAT DOWN HERE IN HAWAII...PLEASE HELP I HAVE NO COOLANT LEAKS JUST FILLS UP, I WAIT TILL ENGINE COOLS DOWN THEN RE POUR IN ENGINE....

Are you sure you dont have a blown head gasket or the word no one wants to hear Cracked head or 2600i was doing the samething and it turned out to be a blown head gasket between the cylinder and a water jacket and was pushing all the water out of the motor

i dont think so i have no signs of a crack head or head gasket blown....i change coolant a while ago and its still green....what should i check instead of taking it to a mechanic....

i have no leaking fluid....fo example if i fill radiator up, then leave no fluid in overflow, then ill drive for hours, then ill see a lil fluid in the reservoir....when does the fluid supposed to return? when the engine cools down?

Did you replace the hose that goes from the res to the radiator? Check the hose that sticks down in the res for cracks or holes also.

it looks fine but ill change it...what else should i check or do

As the engine and coolant cool down in a sealed system, any air in the system also cools down, and that forms a vacuum. That vacuum should suck back coolant from the reservoir.

You should not be running without a thermostat (except for like a day to diagnose a thermostat that is stuck closed). An operational thermostat will NOT inhibit your engine's capacity to cool. I'm in Arizona, and your heat is NOTHING compared to ours.

I'm not so convinced that you bled all the air out of your cooling system when you installed the new radiator. That could cause your overheating issue as well. Did you install a new 1-row or a 2-row radiator in yours? These trucks were marginal with 1-row in my opinion, like the very same truck with exception of a manual transmission came with 2-row. Or you might, as voiced above, have a head gasket issue.

I have 2-row radiator, all-metal, 1988 Cab Plus run AC 9 months a year, 195F thermostat, no overheating, 115F going uphill mountains at 75 mph.

thanks guys it was both reservoir hoses....both had pin holes...damn they were tiny...but i appreciate all the advice

You can scuff up the outside of those reservoirs right where the pin hole is at and dab a spot of 100% silicone there and let it dry good.....of course the reservoir needs to be clean and dry while repairing it to.....and it will hold a vacuum once again. Also, you have to have the rubber hose on the INSIDE of the reservoir also in order for it to pull coolant back out once the cool down and vacuum process starts, in order for the coolant to make it back to the radiator.
My son's Honda Civic was missing that interior tube when we first bought it. I noticed the overflow reservoir was always full and opened it to look and noticed there wasn't a dip hose present!

Yay I was right lol, glad you got it fixed.