2000 Silverado - Heater core clogged?

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?
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No, there is no water control valve on a Chevy. When you start the "cold" engine, feel the hoses on the heater as the engine warms up to see if they both heat up evenly. OR, (and I would not do this if it were my vehicle) you can remove the return hose (on a cold engine) and then start it to see if you have flow through the heater.
The problem with DexCool is not nearly as bad as some would have you believe. The main problem is that too many people don't understand that when they say it doesn't like contaminants, they also mean air (i.e. to DexCool, air is a contaminant).
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2000 Silverado - Heater core clogged? Group: alt.trucks.chevy Date: Tue, Nov 21, 2006, 8:58am (EST-3) From: snipped-for-privacy@yahoo.com (One'sTooMany) 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?
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One heater hose heats up full temperature hot just like the radiator hoses, but the other heater hose stays stone cold. If these is no water control valve for the heater core, then that means that the core itself has got to be clogged, since the entire remainder of the cooling system ( water pump, thermostat, radiator, etc) seems to be working perfectly fine. We'll pull the heater hoses off the core tonight and see if we can back-flush the core with a water hose. It seems very easy to get to everything and the hoses are held on only with spring clips.
Re: the DexCool, he had the entire cooling system drained and refilled at 50K miles back in 2004 before the truck was even 5 years old, and looking down inside the plastic coolant reservoir, it looks very clean inside. Still, I think it might be a wise idea to flush the whole system thoroughly and refill with good old regular green ethylene glycol based coolant instead.
Rich B wrote:

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Back flushing the heater core is in order (back and fort through both hoses with a garden hose ..ie low pressure). I would then fill it with the green antifreeze (cheaper ). Dex-Cool is not required. The problem with Dex-Cool is that if you don't keep it topped up..it's integrity suffers and the brown stuff shows up. Topping up (mixing) with the green stuff also ruins it.
If the heater core is plugged and you flush it...don't be surprised if it starts leaking later down the line. It may not...but I have seen them leak later on because without circulation..the sediment eats up the core.
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