Been reading around on a lot of post about previous heater issues and just want to make sure before I break out the tools. Been driving around for the past few months and noticed while accelerating, I hear a.... sound.. that I could best describe as hair and other "BODILY" fluids being sucked through a pipe coming from behind the glove compartment which is where the core is. Only untill last night did I notice that it was noticably "quiter" in my truck and I no longer could hear that sound. Then this mourning on my way to work no heat coming from vents but fan blowing hard. Haven't been able to check the lines for heat since im still here at work but I just wanted to be sure that Im heading in the right direction. And if I am, what is the easy way to put some pressure through the heater core to get the sludge out if any?

 

Sounds like you are heading in the right direction. Flushing the core is a good idea. I like to disconnect the hoses at the firewall and connect some longer hoses so that you can do the flushing outside the engine compartment.

 

OK I'll do that this weekend. One more question I would like to ask is that while I'm doing this I'm going to flush the coolant in my truck. Upon looking in my resevoir tank, I have a lot of black residue build up upon the sides of the tank. Is there anything I can use that will remove all the grime out of the system. And should I replace my thermostat because my gauge says 170 while at top operating temp and I know thatsa to low?

 

Back flushing the heater core works best. The coolant flows from the hose connected near the thermostat to the heater core. Take that hose off and then flush into the other hose that is connected to the heater core.
You can get some flush at the auto store to help remove the sludge but you will never get it all. Just follow the directions. Removing the block drain plugs while flushing helps get more of the sludge out.
Replacing an old thermostat is a good idea. You can check old or new thermostats in a pan of water on the stove if you have a thermometer. If the temp guage does not come up with a properly operating thermostat it might be a bad sending unit.