1997 Caravan 3.0 litre engine, loosing coolant about a quart every 3 months.
Checked the underneat, and inside the cabin under the heater, but no visable wetness anywhere. Oil is clean, not white smoke, yet the coolant reservior keeps going down.
75000 miles on the engine, I am running dexcool for GM/s extended antifreeze mix.
You were doing very well -- perfectly -- up to this point.
There's your problem. Never use Dex-Cool in any application not specifically intended for it. It can very efficiently attack gasket and seal materials and incompatible solders, causing system damage that ranges from the annoying to the extensive and expensive.
A likely source of your coolant leak is one or both head gasket(s). They can leak such that evidence is very difficult to find. You may want to make use of ultraviolet-glow leak detection dye.
Whatever you determine to be at fault, change back to regular ("green") coolant or use Chrysler's newest orange stuff, which is G-O5 -- a premium coolant also available in the aftermarket that *does not* attack any system materials.
I'm not sure exactly how the 3.0 is laid out. However, on my 3.3L I had a leak between the intake manifold and the cylinder head. It was tough to track down because the coolant usually evaporated off the intake as it leaked out. Eventually with enough looking I was able to catch it in the act.
Or a water pump, or an "O" ring on the water tube under the intake, or the tube itself, or a loose hose clamp on a hardened hose, or a slightly pourous core plug, just to mention a FEW of the causes I've found on my '88 3.0 New Yorker over the last 10 years.
It's still loosing about a liter every 3 months, but I'm not looking for the cause. At 17 years and 240000+ Km I'm FINALLY going to let the "dead horse" lie down, one of these days.
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