Black tar / ooze emerging from radiant system

RemoteRoads

Looking for some diagnosis assistance. We live pretty remote so local assistance is virtually non-existent.

Radiant floor heating unit 10+ years old attached to direct vent propane water heating tank. Yesterday we woke up to the smell of hot plastic and it looks like something black has bubbled out of the air vent (guessing its an air vent, our unit is clearly a discontinued Eco-King and I can't find anything online about how it was setup).

When I cleaned the black stuff off the vent it started leaking excessively and the screw vent cap was too corroded on the inside to be fixed so I know at least I will have to replace that. Ended up having to turn off the radiant system and cut the flow.

Here is a picture of the whole setup with the propane water heater tank to the left and the radiant reservoir at the bottom.

Aside from replacing the air vent does anyone have ideas what caused it to burn and bubble black in the first place? It looks like there is also a bit of black corrosion on the heat exchanger. We've never replaced the glycol and the liquid is a light tan/pinkish color. If my memory serves it was either clear when we built or the lightest shade of pink.

Any ideas would be greatly appreciated.

Lance

Just can't tell from the pic. If wires involved it overheated the materials to a point of liquification. If just leaking, its PH reacted with the plastic. Color could be mold related? Clean it up and monitor it. Some materials do not interact with other chemicals well.

hot_rod

glycol turns to a thick brown or black substance when it goes bad

Is the tubing barrier pex for heating use? Non barrier pex will compromise the glycol quickly, especially if you run it hot, over 120g

Probably time to flush, fill with clean water and a hydronic cleaner, flush again and refill

Do you need to have glycol in the system?