Same truck with 360.Got tired of freezing going down hiway.The big problem as I see it is the heater core is at the same level as dash,leading to air lock when coolant level goes down.The solution is to use a air assisted cooling system filler{air lift by U-view} or the lisle cooling system funnel.When using the funnel you have to run the engine and blip the throttle several times to get air out.This fixed my truck.My heat is excellent.The only nit I can pick is that sometimes it doesnt feel super hot when the system is running wide open.Usually bumping it down a speed causes the heat output to be greater.I think I might try putting a restrictor in one side of the system just to slow the flow down a little to see if that changes anything.BTW,prestone makes a cooling system flush tee that will let you flush the whole system out without having to disconnect a bunch of hoses.I tried fixing my heat problem by flushing,but it really doesnt do anything except clean.Also if you need a chemical that will safely clean out a dirty radiator without damage use citric acid.They sell it at health food stores.2 ounces to a gallon will clean the dreaded dex cool mung out of a radiator.Stronger than that will kill a car battery if dripped on it{that hurt my take home}Good luck and dont believe these trucks just dont blow hot air,ya just gotta fix it, fix it, fix it,just fix it.

 

I would seriously consider the Airlift if I knew it would work. I don't see how drawing a vacuum in the radiator is going to remove air in the rest of the system.
http://www.uview.com/ProductDetail.p...tNumber=550000

 

its because air doesnt exist in a vacuum.

 

Let me start by saying that I am a certified automotive technician. You guys are on the right track but, these trucks have an old style vacuum system supplying the blend doors and vents (ex. defrost, vents, floor). When you have a vacuum leak in one of these lines or the intake manifold or plenum, you will loose the vacuum supply to these doors as well. So when at idle, you might have some heat, but when you rev the engine it demands more of that vacuum supply to the motor and your doors loose thier vacuum supply. Just be sure to check all of these vacuum supply lines as well as you intake manifold for leaks. A simple way to do this is to spray brake cleaner lightly around intake and listen if your engine comes off idle slightly. Dont spray too much though as it could cause a fire. Hope this helps some of you out and good luck. Oh, and another thing is to check the one way check valves in these vacuum lines as well. Just make sure they are'nt plugged up or installed backwards. I actually found one installed backwards on one of these trucks. Probably human installer error. Just realized how old this post is.....lol.