hey guys im a new member here but have been reading this forum for a good long while always great help here! im kind of in a pickle and could use some help! about two weeks ago i purchased a nice little 2001 4.2 v6 standard tranmission 2wd truck for a fair price. needed a couple of minor issues fixed which i took care of the first couple days. after a bout a week and a half of driving i started to notice my temperature guage rising. i noticed that i had no flow in the cooling system so i tore it down and found that the impeller on the water pump had sheared off and was just sitting there. so i installed a new water pump and buttoned her back up thinking that this would be the end of my overheating problems... nope! while i had the radiator off and the water pump off i flushed thru the system with a water hose and thru the radiator from both ways and thru both heater hoses both ways. after filling the system up 50/50 with water and antifreeze and making sure i was at the right level i took it for a test run. i drove about six miles and saw the temp start to climb. i pulled over and let the pressure off of the de-gas bottle not recommended but i chanced it rather than fry my motor. as soon as i let off pressure it went right back down to cool and i started off again. i drove about 25 miles all together abd had to stop and repeat this process about three of four times. i just figured it was working trapped air out of the system. the problem is four days later its still doing the same thing always after about ten minutes of running(my commute time). am i missing something or does anyone know what would cause this? please help i cant go anywhere without pulling over every 10 miinutes... any input would be greatly appreciated!!! frustrated as all hades!! also my heater which didnt work previously now is coming and going... also replaced the thermostat and fan clutch...
thanks in advance for any help or advice!!

 

There are not to many things that can go wrong.
Is the water pump the right one for the year? I ask because the old motors that use separate belts may run the pump the opposite direction.
This often was the results on the old 5L motors that had the old 302 pumps put on them.
Next a head gasket leaking combustion gas into the cooling system will pressurize it to excess. The pressure does not cause the overheating as much as the hot combustion gas as the system normally run at about 15 psi.
The result of blowing a hot system off is the sudden change in pressure to the system. The high pressure raises the boiling point. A sudden drop causes a huge expansion out the fill.
Next the radiator bottom quarter may be blocked resulting in 'reduced' cooling capacity that take time to show until under load.
Past owner overheating may have done more damage than need be from trying to run if after a know overheating problem developed.
You just have to consider all these things and take another look at the situation.
Do cold pressure testing, test coolant for exhaust gas, review the pump part number etc.
You apparently bought a truck with known or unknown issues to the last owner and now have the fun of sorting them out.
Good luck.

 

bluegrass 7 thanks for the advice. i was leaning toward a blockage in the water jacket seeing as how it will idle for an hour even with me revving it to 3000 rpm and it wont heat up until i drive it. any advice on clearing a blockage if that is the case? im starting to think the seller saw me coming a mile away... next one will have a much longer test drive for sure!! i have none of the telltale signs of a cracked head or head gasket but i have not had the coolant sniffed. no water in oil no oil in water or exhaust smell no smoke engine purrs like a kitten just gets hot when i drive it!! scratching my head here!!

 

I would have the radiator flow checked.
Yes you can set all day and run the motor but unless it's under load and making power (much more heat) from burning extra fuel, it may never overheat.
Good luck.

 

thanks alot ill check that out and let ya know!

 

overheating and heater not working is very common for air bubble in system. You need to park front end up on a hill and get the system filled up... or put a TEE in the upper heater hose and fill radiator tank while you vent air out the TEE.

 

i picked up one of the prestone backflush tees and some system flush on the way home gonna try flushing it out tonight and filling it with the tee open and see what happens ill keep ya posted! thanks!