Yea, at least the older Dex formula used to turn solid! I also think it was related to having low coolant too, like exposure to air inside the system when pressurized or some crazy mess like that.I'm low on the miles but I'm pushing 5 years and I'm not sure what the previous owner had done to it. I've got a feeling it was nothing. I've heard bad things about running the factory dex-cool longer than 5 years....
You're on time with maintenance for this, so a simple drain and refill is probably sufficient.
From the Helm’s service manual:
Cooling System Draining and Filling (6.0L)
1. Disconnect battery ground [I would usually skip this step]
2. Ensure engine is below 50*C before removing the coolant pressure cap.
3. Raise and support the vehicle.
4. Place a drain pan under the drain ****.
5. Loosen the drain **** until coolant flows out of the radiator. (Note: If drain **** is not being replaced do not remove it from the radiator.)
6. Inspect the engine coolant for the following conditions:
a. Discolored appearance – Follow the flush procedure.
b. Normal appearance – Follow the filling procedure.
1. Tighten the drain ****.
2. Lower the vehicle.
3. With the engine off, remove the coolant filler cap.
4. Slowly fill the cooling system with a mixture of 50/50 dex cool and water until coolant flows out of air bleed hose spigot. Refit air bleed hose.
a. Note: When pouring coolant take care not to spill any coolant onto the accessory drive belts. If spilling occurs, rinse the belts immediately with water.
[I think the manual has an error here, because it does not include a step for the 6.0L motor to remove the air bleed hose mentioned. However, the 3.6L instructions for filling has an extra step that says: “Remove the engine coolant air bleed hose by releasing retaining hose clamp and remove it from the radiator spigot.”]
b. Note: Lift the radiator top hose underneath the air intake tube, to release air bubble in hose, top up if level drops.
5. Start engine.
6. With engine idling top up coolant until full, wait for several seconds and “top up” if level drops.
7. When full, fit coolant filler cap and switch off engine.
8. Check coolant level in coolant recovery reservoir. Adjust coolant level in the reservoir to the top of graphic mark on the dipstick.
Change the fluid at 5 years and done with it.My dexcool was still good at less than 40,000 miles but the 5 years was up.
In the short run: If it doesn't need much coolant, then I'd add plain water. Before winter, check the freeze point after the water has had a chance to mix with the existing coolant. You'll need the correct antifreeze tester for whatever type of antifreeze it is, which will be a problem, see below.Wolds i started a thread called Flat Hose. I could sure use your input. I went to add coolant to my radiator, but noticed it has pink coolant in it. the Dex Cool i have seen is Orange. i am afraid if i add anything and mix it, it will damage the system. Any help is appreciated.