Worked on my truck the other day and when I was done I forgot to put the clamp back the on top radiator hose and I went driving around and when I parked and got out I smelled a "hot" smell and saw antifreeze leaking under the truck. I realized what I did and put the clamp back on and put some antifreeze in it and went back home. Ever since my water temp never gets to the middle of the gauge like it used to, now it just goes about a 1/4 to a 1/3 of the way there. Any ideas?

 

Likely air was sucked into the cooling system. Try burping the radiator.

 

Burping it with the truck running?

 

Yep. If you can park with the nose on top of a slope even better.

 

Definitely air in the cooling system. Just run it from cold with the rad cap off and let it "burp" the air out. As the air comes out, put more fluid in. Once it heats up all the way, shut it down, let it completely cool, top off the fluid and you'll be good to go.