I guess by water you mean the engine coolant. If you getting oil in there, then you have a problem. Your cooling system is under pressure when your driving, and it cools and loses the pressure. It could *could* get sucked back in cooling system when the system cools. But really, the problem is not that you have oil in there, that won't really hurt anything. The problem is that there is a way for oil to get in there. You engine needs some serious work. The head gasket is a lucky culprit. The head needs to be removed to really figure out what's going on under the hood. But, if your going to let your wallet go for a mechanic to play with your car and find out your problem just to tell you that you need $$$$$$$ to fix whatever it is, I would say just get a new motor. For a 1996 Civic, I bet you could find a decent motor within 25 miles of your house. I hope this helps.