Water is a natural by product of the catalytic converter, When the exhaust is hotter then the inside surface of your exhaust system, you produce condensation. That causes condensation everytime you start up the vehicle, in cold weather, you produce more. If you run the engine long enough, it will empty the water from the low lying areas, which is why you should not just jump into your vehicle in the winter, drive 1 mile and stop it. That will rust out your exhaust quickly. In the summer, you produce less condensation because the pipe and the exhaust stay at a closer temperature which produces less condensation.
Engine knock, you should check your oil level, if normal you may be hearing your lifters tick from age.
〉 Answered on Oct 12th, 2010 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions
I am assuming you have owned your car for sometime. This water from the tailpipe can be a normal condensation condition depending on the climate you are in. Have you just noticed it? Did the water start when you started to hear the knock? Do you have oil in your engine? Is there smoke coming from the tailpipe with the water dripping? Do you see any leaks on the ground? Depending on the mileage of your car, and the maintenance you have done, your knock might mean you need to do a different type of maintenance, like using a heavier weight oil. Or on the extreeme, you have engine damage. It can go either way. My best suggestion is to have your car checked. These are questions you need to be prepared with when you bring your car into the repair shop. Perhaps they are related, but maybe not.
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〉 Answered on Nov 12th, 2010 by Audra Fordin, Owner at Great Bear Auto Shop
Not related. Water is condensation and the knocking could be low oil it weak oil pump. Best checked out by a repair shop.
〉 Answered on Nov 12th, 2010 by Barb Petrey, President - DBK Enterprises Inc at Jiffy Lube