2000 Volkswagen Beetle leak in backside of engine

I am assuming you mean a coolant leak..? Is your vehicle overheating? Do you see any coolant leaking around the water pump? If there is no visible leak than there is a good chance that your coolant is leaking into your engine. Check your oil to see if the oil level is higher than it should be or if the oil is watered down. A blown head gasket is usually the cause of this.