first off let me say that i am very glad i stumbled onto this site. lots of good info here. ok, to my problem

i have a 1996 dodge ram 1500 with the 5.2 in it. no mater what i do i cannot get it to stop overheating. i got it cheap from my step dad because he upgraded to a newer truck.it has about 110,000 miles on the rebuilt engine.he replaced the waterpump on it about a year and a half ago but it has been sittin pretty much ever since then because of the overheating problem.i checked the thermostat and hwen i saw that one side of it was completely broken off so i figured i had found my problem. i replaced it with a 160* theromstat.fired it up and had the same problem so i got some radiator flush and flushed the rad.did not change anything. the temp still creeps up to about 250 if you drive it even a couple miles. so then i dissconnected to fan clutch temp sensor so the fan would run all the time to see if it was bad. still did not help the problem. i am not losing any coolant and the oil has no water in it and neither does the exhaust.

what can i do to fix this thing?

 

If it has done it ever since he had the new pump put on, I'd start there.

 

i just talked to him about it and he said he put the new one on it because the old one gave out. he said that he drove it for a couple of months after he replaced the pump and then it startd over heating

 

Is there a possibility that the temp gauge or sending unit is bad?

 

it very well could be bad but i dont know for sure. when it gets hot like that i can turn the heater on and it will drop all the way back down to about 160 or so until you turn the heat back off

 

Does the upper hose get hot? Sounds like it's not circulationg through the radiator. Could be air locked.

 

yes the upper hose gets really hot.how do i un airlock it? do you think the water pump might have went bad again?

 

If the upper hose gets hot, it's not air locked. Can you see through the radiator. If it's circulating, it should be cooling. What is the fan clutch temp sensor you talk about. Didn't this truck come with a hydraulic clutch fan? Did someone put an aftermarket electric fan on the truck? If so, it may not flow enough air(CFM).

 

i am talkin about the little coil on the front of the fan cluth,i read on the inter net how you can take a screw driver and un hook the coil and it will not allow the fan to free wheel. it stay engaged the whole time.

 

some random thoughts.
by seeing the temp gauge drop when the heater is turned on tells me a couple of things.
the temp gauge is working well enough.
the engine will run about normal temp if it has a cooling path through the heater core.

you might have a blocked thermostat
you might have a stopped up radiator.

i'd start at the beginning.
flush the block, heater core, hoses, etc, including removing the block drain plugs hiding behind the motor mounts (if you can get them out, might require vise grips)
remove t-stat housing, look for pieces of gasket or pieces of t-stat. temporarily reassemble with NO t-stat. leave top radiator hose unattached at radiator.

using water hose, fill up engine block through top hose. fill up radiator and leave hose in rad cap with water running.

this takes about 3 sets of eyes - start truck and let it run for awhile. with no t-stat, it'll be pumping warm water like hell out the top hose. monitor that and see if it spits out any debris like a broken gasket or something. monitor radiator that it stays full and provides plenty of cold water to engine. monitor engine temp, it should stay cold.

if anything unexpected happens - stop. you're testing a lot of things here... water pump, radiator flow, etc.
if your radiator is stopped up, then the level won't drop and the engine will overheat with NO COOLANT - so pay attention !!

if all is well, connect top rad hose to rad. continue to monitor.
if all is well, top off rad and put the cap on. continue to monitor.
if all is well, test drive it some.
if all is well, install new 180 or 195 t-stat. test in kitchen first with cooking themometer.

i'd expect the new water pump to be ok.
i'd guess your radiator might be stopped up. if its ever been run with tap water, it'll stop up with mineral deposits, which might have happened after the water pump replacement...