i asked this on another ford forum also to see if i can get an answer. thanks

ok i'm asking for the neighbor on this one. he has the 2000 v8 4.? engine and this summer he had the radiator fill tank full of some green or brown sludge. so he removed the hoses and flushed what he could out of the system and filled with water so he could continue the flushing if needed until the system remained clear. well it may have worked then as he did refill with coolant that was said to be universal coolant. anyway this week he had it overheat and the coolant he said was way down.i did see coolant seeping from under the t/s housing so that may be warped and causing the coolant to leak out enough to make it overheat. i was helping with some troubleshooting and i did not see any bubbles in the overflow. but we did find this issue. when idling the heater hoses stay cool and he removed the flush cap and no coolant was in the return heater line. also he took off the return radiator hose and no coolant came from the hose but did pour out the top of the radiator until it leveled off in the radiator. he has no sweet coolant smell in the exhaust or the cab so i'm not thinking a bad heater core or head gasket yet. but i'm wondering about the pump. when he revs the engine the heater hose gets hot and i can feel some heat in the top radiator return line but only along the bottom of the hose.

so outside of a bad head gasket. what can cause this no heat still no heat until revving the engine i'm leaning to a bad water pump. thanks for any help. bp.

 

ok update. took off the water pump and it was not bad as far as the impeller goes. it did not leak and the bearings did not have any sounds like it was failing so he kept it but put the new pump on to make sure.

he still can't get heat when idling. i took my ir temp probe and measured the inlet to the heater and got 160 deg the outlet on the hose was 90 deg so the heater is removing the heat there. the radiator had 120 to 150 going in the upper hose and 80 deg at the outlet side so the radiator is removing the heat. but this is the issue i have never seen ever we took off the top hose and with the t/x housing at 180 deg no water was coming out the hose.

i told him for s/g to drain it and take off the lower hose and see if that hose is plugged up. being the temp was slower at the outlet than the inlet it looks like the radiator is not plugged. but if he takes off the hoses we are going to put water in the radiator and then remove the lower plug and see how the water drains out. it is possible the radiator is plugged up! outside of that i have not more ideas. unless someone here has some ideas to send along. thanks

 

Might be the radiator hoses are failing from the inside out?
Is the thermostat new? If not try a new one.
Some time air bubbles can get trapped and when they get worked out they can cause rapid drop in coolant. Try to refill on a slight incline to aid in working air pockets out.

 

we did that. and i told him he may have the lower hose collapsing. i told him to drain the system and take the hose off and check. also i noticed if he leaves the tank cap off the upper hose is soft to the touch you can squeeze it but when he puts the cap back on the upper hose gets firm to the point of no being able to squeeze it at all. almost like the radiator is plugged up but when i did a temp on the radiator it had heat on the top hose side and dropped almost all the heat ton the tank side.

one more thing does the heater hose have to have that restrictor in it? for now he just bypassed the heater entirely and i told him it was going to be an awful cold ride this winter with out the hear. not to mention the defrosters.

thanks