basically what happens is if I go faster than 70 in my truck it begins to overheat, it doesn't get all the way to the red but it definitely goes above the half way mark, and it wont go above that, and when I slow down the temperature goes back down to little under halfway fairly quickly and then after a little while will return to normal. any idea as to why it is doing this

 

Check your radiator for debris, the air flow may be restricted.

Or it could be the water pump is shot inside from corrosion. Do you change the coolant on a regular basis?

 

depends on what you mean by regularly, either way for the last few months or so it was leaking through the heater core (I think) but I got it to stop with bars stop leak and before that it was replaced probably about a little under 3 years ago when I last replaced the heater core, so the current coolant is about 3 weeks old

 

You could have a blockage in the radiator-not un common on older vehicles with stop leak added. When it gets warmed up (regular operating temp) shut it off and carefully feel the radiator at the bottom and then the top. If there is a difference in the temp from top to bottom, the radiator is probably partially plugged.

Also look at the front of the radiator for bug/mud/junk not letting the air flow through.

Coolant should be changed about every 2 years-after that it starts to turn acidic, or so I've been told. then it can start to eat parts inside, like the impeller in the water pump. If that has happened it can't move the coolant through the system fast enough and heat starts to go up.

Good luck.

 

+1
In my older Fords when ever I added stop leak of any kind the same exact thing happened to those trucks when going at high speeds. It would get hot as I went faster. I took the radiator out and un soldered the end caps and took a flat rod to clean out the ribs. Or you can take to a radiator shop and they will do it for you. And last resort buy a new radiator

 

sounds good I will check that out today