I have a 96 Chevy Silverado with 350 the heat doesnt get hot when its really cold out when its around 40 degrees out it is hot but when its 20 out it is luke warm....I have replaced my radiator recently....And there is a gurgling noise from under my dash when I accelerate maybe from the heater core...Any Ideas??

 

air trapped in the heater core

 

I have the same problem in my s-10, but I do not hear the gurgling sound, I also had to replace the radiator recently. How would you go about relieving the air in the heater core without tearing the dash apart to get to it?

(I know, wrong forum for the S-10 but same problem)

 

After changing a rad or hoses, I would always run it a couple of days with the rad cap loose. Along with squeezing the upper rad hose several times.
The flow with the heater on full heat should push the air out.
If your heater core is higher than the top of rad Ihighly unlikely) you could park it on a steep up hill for a bit.