I have a 2005 Silverado 5.3L with duel temperature controls. On cold mornings I let the truck idle for anywhere from 15 to 30 minutes with either the airflow selected to defroster/floor or the dash panel vents and with both temperature zones set to their warmest positions, and the blower fan set to the highest speed. When I get in the cab is still ice cold and there are no signs the defroster is clearing the windsheild, even with the engine temperature gauge showing about 205 degrees. I do not get any warm air from the heater or defroster vents until I drive about 1/10 mile, then there is plenty of heat. What are the possible cause to this type of problem? Where can I find info on how to repair the problem myself if not a major undertaking? Thank, SDB

 

I have the same problem anyone respond to your question???

 

My problem turned out to be caused by a very small leak around the water pump. I started noticing a slight smell of anti-freeze around the front of my truck after driving which lead me to the cause of the problem. Also, as the coolant level was getting lower, the problem began to get a little worse. The heater began to blow out cold air while I was setting at traffic lights and when I was driving at slower speeds and not excelerating the engine. I replaced the water pump and flushed the cooling system to correct the problem. Now, I have heat to spare!

 

My problem turned out to be caused by a very small leak around the water pump. I started noticing a slight smell of anti-freeze around the front of my truck after driving which lead me to the cause of the problem. Also, as the coolant level was getting lower, the problem began to get a little worse. The heater began to blow out cold air while I was setting at traffic lights and when I was driving at slower speeds and not excelerating the engine. I replaced the water pump and flushed the cooling system to correct the problem. Now, I have heat to spare!

 

I agree with relgibds

 

I know it's three years old but I had something to add.

If you have a cooling system problem, like you notice it's leaking it's safe to drive the vehicle home, to a shop wherever as long as you still have heat coming out the vents. As long as you feel heat there is water circulating and cooling your engine. As soon as you feel a drastic drop in temp you need to pull over, you're out of coolant and it's not circulating anymore.
It's just a little trick to use to limp home instead of towing if it's a reasonably small leak and you won't do any damage to the engine.

Works in summer or winter.
Ended up here looking for help with my defroster. Still looking.