What can cause oil go to coolant system?

(2011-06-17 14:20:40)

1. Andrew R Says: its dirty black/brown oil. it doesn't heat up. the rest of the car looks ok.
ive been told it might be because someone accidentaly put oil in there but if so why is it black?

2. going_for_baroque Says: You know that oil flows through the motor and coolant flows through the motor. The place where they're close to each other is in the head, sealed by the head gasket. If the head gasket has failed, oil could be leaking into the coolant. Confirm this with a good mechanic. If it's a small leak, none of the rest of the motor need be affected, but your cooling will deteriorate eventually, plugging the radiator and leading to more serious problems. Might need a cooling system back flush now, even after you resolve the oil situation. Remember to back flush the car's heater core, too. Take care!

3. CH4RL13foxtrot Says: A failed head gasket would be the most common cause of oil in the coolant. You might want to check the oil, too. It it has light colored goop in it, you're definitely getting oil/coolant transfer across the head gasket barrier. White (or very rarely, blue) smoke from the exhaust would be another symptom to watch out for.