Beetle 1.8t puttering like a diesal

Could it be the timing belt tensioner or water pump? Have you had the timing belt changed yet? HAVE IT CHECKED NOW!!! :-) But it may be the shield over the exhaust or exhaust manifold and you hear vibration. Not sure how the NB 1.8t setup is though. loud puttering sounds like a diesal engine and it is also making a sound

I had the water pump replaced last summer so I wonder if it could be a defective part. My temp light has come on red a few times during first starting out on cold mornings. Would the water pump make that noise? Would the timing belt make that noise?

If a shop did the water pump......take it back to have them look for the noise and check the temp light out. Probably some part that revolves is making that noise, but it could be a vibration also. Water pumps, timing belt tensioners, alternators, a/c compressors, etc. I have seen partially frayed timing belts hitting certain engine parts creating a noise.

A. Follow Dave's advice.

B. "Knocking" sounds like marbles in a muffled coffee can. Once you have heard it for the first time you will never mistake it. Diesel engines 'knock' because they use compression-ignition, which is analogous to 'knocking' in a gasoline engine... premature ignition.

Then: You could have skipped a notch on the timing belt you could have bad gas, you could have a partially clogged filter so the vehicle is running lean, you could have something as simple as a loose heat-shield combined with mild knocking.

Peter Wieck Wyncote, PA