I bought a 2002 audi a4 1.8t quattro last month. So far I've done the coils twice and just last week the car was overheating due to the water pump. I bought it back to the private dealership I bought it from to change it and just got the car back today. The hp doesn't seem the same and I have a lil bit of oily substance under the protector under the car. I was told it is normal because all of the things you have to do to the car to replace the pump. Is it true??