Does a 2000 Silverado (5.3 V-8 engine) not have any water valve in line with the heater hoses?
The heater in my neighbor's pickup truck is blowing cold/lukewarm air. It used to be able to melt your shoes, even as recently as last winter when I remember riding in it, the heater worked great. The truck only has 75K miles on it since new, and has that red "Dex-Cool" antifreeze in it, which I've read many bad things about on the Internet. Everything about this truck looks to be in pristine condition, so when he asked me to help him troubleshoot the heater blowing cold (first use of the heater this season) I immediately suspected a hot-water control valve issue, like most vehicles have in-line with one of the heater hoses, but this truck appears to not be designed with such. The heater hoses appear to go uninterrupted from the engine/thermostat casting, direct to the heater core in the firewall with no valves inline. The engine's thermostat appears to be working correctly, as the engine warms up to full operating temperature at a normal rate, and stabilizes about 205 deg indicated on the instrument panel. One heater hose gets very hot -- full temperature, but the other stays very cool. Is this simply a clogged heater core? Can a heater core on this truck this young clog so quickly in just 1 year's time from having worked so well last winter? I've seen clogged heater cores on very crusty old vehicles that have had very poor or no maintenance of their cooling systems for decades, but this truck has always been maintained immaculately, and is in pristine condition. I guess I'm just having a hard time coming to grips that a heater core can clog up so quickly and completely on an only-6-yr old vehicle that's been taken care of so meticulously... but those stories I read about Dex-Cool antifreeze turning to jellylike goo sometimes. Is that likely what we're encountering in this truck?