Have a 92 camaro 5.0L that is getting no heat. New radiator, heater core, hot-water valve, blower fan, pretty much everything in the heating system is new except for the water pump, but no signs of that having a problem. I've replaced the thermostat twice, just in case the first was faulty, but no change. The engine once hot (which takes about 20 minutes) sits at about 165 degrees acc'd to the dash temp gauge. Can't figure it out. Do water pumps ever " half work"? Usually they either work, or die right? It gets normal heat if the temp outside is 40 deg. Or higher, but lower than that, just cold air blowing from vents, and considering I'm in Wisconsin, and its -10 deg. Right now, driving is not fun. Any help would be great.
First of all you may not have enough fluid in the radiator. Make sure you have enough of a 50/50 mix of antifreeze. Secondly you may have air in the sytem. With the car running at operating temp I would open the hood and check the hoses going to the heater core. Make sure both of the hoses are hot. If not I would check out that heater valve again. If both are hot maybe when someone put the new heater core in they might of messed up under the dash and may have a duct binding and not opening all the way. I have also heard of water pumps having a bad impellar but if you can look into the radiator you should be able to see some flow especially being you have a new radiator. My bet is low A/F or air in the system but do the checks I suggested. Hope I was of some help.