* Contamination with oil: If the coolant has a milky or oily appearance and is thick, this is a serious issue suggesting a head gasket leak or a crack in the engine block allowing oil to mix with the coolant. This mixture creates a sludge-like consistency. This needs immediate attention as it can severely damage your engine.
* Degraded coolant: Even without oil contamination, coolant degrades over time. Yellowing can be a sign of this degradation, especially if the coolant is old. The additives that protect your engine start to break down, resulting in a thicker, less effective fluid. This is less serious than oil contamination but still requires a coolant flush and refill.
* Incorrect coolant mix: If you've added the wrong type of coolant (e.g., mixing different types, or using tap water instead of distilled), this can lead to a thickening and discoloration. Different coolants have different chemical compositions and mixing them can lead to precipitation and clogging.
* Corrosion by-products: Over time, corrosion within the cooling system can release particles that can cloud and thicken the coolant, leading to a yellow tint. This usually accompanies degraded coolant and highlights the need for a flush.
What you should do:
1. Check your owner's manual: It will specify the correct type and concentration of coolant for your vehicle.
2. Inspect for leaks: Look for any signs of leaks around the engine, radiator, hoses, and water pump.
3. Test for oil contamination: If you suspect oil contamination, take a small sample of the coolant and look for oily sheen or milky appearance.
4. Have it checked by a mechanic: If you're unsure of the cause, or if you suspect oil contamination, take your vehicle to a mechanic for diagnosis and repair. Ignoring a problem like this could lead to very costly engine damage.
Don't drive your vehicle if you suspect a head gasket leak or significant oil contamination. This could cause catastrophic engine failure.
