heater issues!

working on an 05 dmax here. the heater will not get warm. replaced the heater core, and the thermostats. also the temp gauge gets hot to when driving it for sometime. the hoses that go into the firewall to the heater core are cold also after its up to temp. Also the EGR cooler is cold also. Anyone ever had this issue? its like the EGR cooler is plugged and coolant is not flowing through it but then i took the hose off the cooler that feeds the heater core, i filled the reservoir up with coolant and there was some coming out of there. but when i start it nothing comes out.

Is the EGR blocked? Might be why the cooler is cool. As far as the heater, have you tested the coolant to see if it's good ?

if the truck is running hot and the heater is not working could it be that the water pump is not pushing the coolant through the engine?

^^ True. Use a temp gun and shoot the coolant bottle and the upper hose/ t-stat housing to check for a difference.

the egr is not blocked. we pulled the hose off coming out of the egr cooler and started the truck and nothing comes out. and the hose before the cooler is hot. Im going to get a EGR cooler delete kit and completly get rid of if and hopefully it will fix the problem. I called GM tech assist also and they told me to put a EGR cooler on it because its sounding like its not flowing coolant through to them also.

if it's not flowing I'd bet it's the water pump. check the temp difference in the manner I posted and I bet there's a good difference