if it heats your cab well, then i'd say it isn't clogged or anything. if there's no signs of leakage in the cab, i'd say it hasn't rotted yet.
and actually I haven't heard of many issues with heater cores from trucks like ours as of yet. mainly just getting clogged from using radiator 'stop leak' products lol

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1999 xlt 2.5l 5-speed Supercab 159k
83 diesel 2.2l na
06 F250 6.0l psd
{click for lol}

Yea I can't see any signs of wetness in the cabin and the heat gets hot.. most of the time I have to keep it right in the middle because any higher and it's just too hot for more than a couple mins or defrosting the front window..etc.

When I flushed the system I made sure I ran not only water in through the core but also air, and both tubes flowed air and water so I don't think a clog is there. I know I didn't have heat in the beginning as I think air was trapped in the core but after 10 mins it started getting warm, now it's fine and hot.

Thanks,
-Nigel

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2001 Ranger XLT 2.3L Auto: Bunch of misc mods.
Little lift: 4" Spindle Lift w/ 2" shackles and 2" oem blocks.OEM Ranger Sport Wheels: Tires=245x75x16

~NSG~

Smell + fog on windshield are the usual signs of bad news. It's normal for a small amount of coolant/water to evaporate over time, keywords are small and time. Maybe top it off with a few ounces a once or twice a year. You could always borrow/rent a cooling system tester. Hook tester to your system via the cap location on the radiator, pressurize, come back after a period of time and see if it's dropped.

It is possible for the heater core, like the radiator to "rot" but rot probably isn't the best word. Not maintaining good coolant will shorten the life of these two items. The reason is, coolant contains corrosion inhibitors, there is a chemical reaction between these corrosion inhibitors and the engine block/heads; over time the inhibitors are depleted due to the reaction, now there are no corrosion inhibitors, and corrosion begins. The other thing that happens to both heater cores and radiators is that they experience cyclical fatigue due to thermal stress. Every time the vehicle experiences a duty cycle, these items are heated, they grow in size a teeny weenie bit, there's bends and corners that flex and bind, stresses develop. Turn off the key, these operating stresses go away. However, fatigue damage is cumulative, it doesn't go away and over time the part simply wears out due to usage. Such is life. Just for fun, take your DVM, set it on a real low DC voltage setting, put one probe on the vehicle chassis (ground) and stick the other probe into the coolant after you have removed the raditor cap. Surprise, surprise.

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2004 Ranger FX4 Level II, 5R55E, Sonic Blue Pearl

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