hey guys, with the "cold weather" and rain finally hitting socal, my 260z has been making a really loud noise in the morning and also at night time when i leave work. the car was running fine throughout all of summer until it began raining. its sounds like a high pitch gritty rusty old wheel. when its happens, the engine also experiences low to medium vibration. I double checked the belt tension and everything looks good but the noise is still present. Most of the time it will only make a loud noise when i rev it up to turn on the alternator, but not always. I have a improperly wired 280zx alternator, so the alt turns on only when i rev past 3500~ rpm (the wiring on this car has been butchered by previous owners so the voltage regulator rewire causes a weird battery drain when the car is off). anyway, the noise and vibration eventually goes away once the car has been driving for atleast 10 minutes. the noise appears to be coming from the fan clutch/water pump or the alternator. its so loud i really cant discern the exact source. any suggestions on how to further diagnose this?

 

If you have factory AC, check out the AC tension pully bearing

 

its the crankshaft pulley!

its a 2 piece design (wtf nissan engineers) and the alt/waterpump pulley has about 7 mm of play and rubs the front of the engine... fml. the front pulley for the ac compressor has no play at all. can i switch to 1 piece designs? are there 1 piece designs?

 

The "weird battery drain" is caused by the fuel pump relay. Nissan designed the fuel pump to get switched on by one of two relays. The coil for relay 1 is powered when you have the key in START. The coil for relay 2 is powered when the alternator is turning. It's wired between the alternator and voltage regulator.
Eliminating the voltage regulator made it where the battery was connected to the fuel pump relay. It could be prevented with a diode in the right place.

 

well the i looked under the car for the external pump. i just see an empty bracket and a hanging connector. it sounds like a relay still kicks on as soon as i connect the battery with ign off. it seems to coming from the drivers fender area. but i think the bigger priority is the crank pulley. this is my daily driver so i need to take care of that first...