banshee underhood noise when cold

[Re037]

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 is fully warmed up. 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?

[evildky]

Does the noise happen everytime you do a cold start? Only makes the noise when you rev? Does the fan clutch turn ok by hand? Feel gritty? kinda sounds like alternator bearings.

[Re037]

well, its not the alternator... 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?

[evildky]

The Nissan Motorsports crank pulley/ harmonic ballancer is a single groove but being a harmonic ballancer it is still technically 2 piece. If you want to run a/c depending ont he kit you'll need a 2 groove pulley or the add on pulley that bolts to the front of the stock pulley, the 260z did not come with factory a/c it was a dealer add on so you cant really blame this one on the nissan engineers, it's the aftermarket engineers.

[Re037]

ahhh, interesting solution they made for ac. can i use any l28 pulley with ac for this? my 260 has a L28 (n42 block/p90 head)

[evildky]

the blocks are all the same, the later 280zx a/c bracket from nissan puts the a/c low on the drivers side, there are a number of add ons that locate the a/c above the alternator some use the second groove some use the add on pulley. I'm not sure where the fcatory a/c s30's place the compressor but if memory serves the a/c lines come out the firewall on the drivers side which woud mean it's similar to the 280zx mount. Carb'd cars came with an air pump in that location which is why the aftermarket put it high on the passanger side, that and their add on a coil hung int he passanger foot well. Yes you can use any L6 pulley on any L6 motor, the 280zx units are ehavier and the earely 240 ones and lighter.

[Re037]

my ac compressor is actually right below the air pump on the drivers side. the air pump belt connects to a double groove ac pulley. i thought that was odd. but thanks for the info evil!