CincySoot
Member
3 days and 15 miles ago, a foreign car repair shop replaced the alternator in my 2001 jetta tdi (ALH) 5-speed with 200,000 miles. This morning driving to work I suddenly started hearing a metallic knocking / rattling / ticking that changed with engine rpms. I did not notice any loss of power with this. I pulled off, stopped the engine and restarted. Noise still there. Opened the hood and it was a scary loud metalic clacking. Nothing was visibly shaking loose (any more than normal vibrations). The tensioner "rod" was not bouncing around. The sepentine belt appeared to track normally. The alternator and AC compressor were not shaking. Shut if off again. Oil level fine. Coolant level fine. Half a tank of fuel and ambiant temperatures in the mid 60s(F).
I drove it back to the shop that did the alternator work, but before I even got there the noise stopped. It's running normally now. Total duration of the sound was about 1 minute of engine running time. The shop wasn't open yet anyway, so I drove it work without further incident. Timing belt is not frayed or making any roller "swishing" noises.
What could have caused that problem?? I'm fearful wondering if something is damaged and will it happen again. The sound made me think of bad things like broken injector pump, bent rod, stuck valve, dead valve hitting the piston, timing belt skipped a tooth... When I get home I'll check the timing on the VCDS. What could this be?
Any theories, warnings, or further diagnostic tests to try would be most welcome. Threads here suggest the alterator pulley, but that always seems to coincide with the belt jumping around(?)
More maintenance history: The timing belt was replace (on schedule) by me at 180,000m, plus t-belt tensioner, water pump, etc.. Nothing unusual to report about that job. The car used to be a greasecar, but at about 190,000m I took that system out because of lack of use lately / lack of fuel / wearing out hoses. At that time I replaced the injector pump seals that had just started leaking. Cleaned out a few gummy WVO bits that formed up in the oxygen-exposed areas of the pump. (Enjoyed using the hammer-mod to get the injection quantity just right). Replace the fuel filter around then too. Nothing else to report until the battery and alternator failed last week and I used this shop (for the first time) to replace the alternator.
I drove it back to the shop that did the alternator work, but before I even got there the noise stopped. It's running normally now. Total duration of the sound was about 1 minute of engine running time. The shop wasn't open yet anyway, so I drove it work without further incident. Timing belt is not frayed or making any roller "swishing" noises.
What could have caused that problem?? I'm fearful wondering if something is damaged and will it happen again. The sound made me think of bad things like broken injector pump, bent rod, stuck valve, dead valve hitting the piston, timing belt skipped a tooth... When I get home I'll check the timing on the VCDS. What could this be?
Any theories, warnings, or further diagnostic tests to try would be most welcome. Threads here suggest the alterator pulley, but that always seems to coincide with the belt jumping around(?)
More maintenance history: The timing belt was replace (on schedule) by me at 180,000m, plus t-belt tensioner, water pump, etc.. Nothing unusual to report about that job. The car used to be a greasecar, but at about 190,000m I took that system out because of lack of use lately / lack of fuel / wearing out hoses. At that time I replaced the injector pump seals that had just started leaking. Cleaned out a few gummy WVO bits that formed up in the oxygen-exposed areas of the pump. (Enjoyed using the hammer-mod to get the injection quantity just right). Replace the fuel filter around then too. Nothing else to report until the battery and alternator failed last week and I used this shop (for the first time) to replace the alternator.
