monday afternoon i was fiddling with the AFM to lean out the mixture - my wife was driving behind me and said the car smelled very rich and was "making smoke" when i would accelerate. popped plugs - a little dark, some oil on a couple of them, leaned out the AFM via the spring wheel/gear by 4 teeth, took it up the street to a long gradual hill for a load test. from stop i punched it up to 5K in first, then second up to 5K then clutch in, turn off key, coast to stop, check plugs, lean out some more. did this twice - on the second time, i revved to 5,500 and the brake light came on (odd) right before i turned off the key. when i started her up, there was a strange whining/whirring sound - thought it might be the alternator. the charge gauge started acting a little erratic and a couple of my relays were buzzing (the one under the passenger seat, and one up under passenger footwell). i took out the crusty, 35 yr. old alt. and figured i'd take it apart to see if it needed some TLC - it basically disintegrated in my hands.

so, new alt. and belt went in last night and refreshed the connections. she started fine and charge gauge looks normal (all the way to right), but i still have that strange whirring/whining sound, almost seems like it's coming from my valve cover area... quick test drive and she feels down on power, a little breathless, and i hear a high-pitch almost whistling sound inside the cabin.

i'm worried i damaged something on the load tests... any thoughts? i'm afraid to take her to work this morning for fear it might be a tow truck home, and i certainly don't want to have a major catastrophe if i need to replace a part before it grenades inside the engine.

just when she was starting to run really well, go figure.

thanks in advance,

geoff

Is it a whining noise? If so, it could be your water pump bearing. It sounds like your car might have been sitting for quite some time, so rusty bearings are always a possibility. Your water pump bearing might be whining because you have a different belt tension, and the noise might go away on its own. But it could be a forewarning of a water pump failure sometime down the road. Or you could have a bad alternator bearing, depending on the quality of the rebuild.

FAIW, you can buy a mechanic's stethoscope from your local Harbor Freight for a few bucks. You might even find one at your local auto parts store. You can use it to probe around your engine to find the source of the noise. Please DO NOT use the lauded "long screwdriver to your ear trick" when working around spinning pulleys and fan belts! And be careful when probing those areas even with a stethoscope.

Do you have AC? Pretty common for the bearing in the tensioning idler pulley to go bad. It's easily replaced, and the bearing is a common one, readily available.

You can run the engine for a short while with no belts. The battery will power the EFI, and it won't overheat for the few seconds necessary to listen for noises, with no coolant pushed from the water pump.

thanks for the replies - a little clarification:

- the whirring/whining sound started right after the second big "load test", accompanied by the alternator acting up (original belt tension)

- new alternator, new belt, (new tension) the sound is still there and i'm pretty sure it's NOT coming from the new alternator

- no AC, only belt is going around crank/fan/alt

- noise seems to be coming from mid-to-rear of engine, not up front

my big concern is how the power seems to have dropped - not sure what i may have done to my poor little z...

i will pick up a stethoscope from HF on the way home and run it w/out any belt (fan noise is distracting anyway) to try and better locate noise

Where are you in Seattle? I am currently in Mukilteo.

@ Blue: i live in magnolia - by discovery park, commute to the east side for work.

are you visiting? your avatar shows canada...

let me know if you have the time/inclination to meet up, as i'd be happy to buy you a cup of coffee and ask a few questions

Edited April 23, 201411 yr by rossiz

Is it a whining noise? If so, it could be your water pump bearing. It sounds like your car might have been sitting for quite some time, so rusty bearings are always a possibility. Your water pump bearing might be whining because you have a different belt tension, and the noise might go away on its own. But it could be a forewarning of a water pump failure sometime down the road. Or you could have a bad alternator bearing, depending on the quality of the rebuild.

FAIW, you can buy a mechanic's stethoscope from your local Harbor Freight for a few bucks. You might even find one at your local auto parts store. You can use it to probe around your engine to find the source of the noise. Please DO NOT use the lauded "long screwdriver to your ear trick" when working around spinning pulleys and fan belts! And be careful when probing those areas even with a stethoscope.

Yup, I experienced that water pump failure 75 km from home.. I'd recommend anyone who's Z has been in storage for a long time: replace the water pump !

@ Blue: i live in magnolia - by discovery park, commute to the east side for work.

are you visiting? your avatar shows canada...

let me know if you have the time/inclination to meet up, as i'd be happy to buy you a cup of coffee and ask a few questions

I'll try to arrange for fri or sat if i'm feeling better. Caught a darn cold and would not want to pass along. Pm me your number and we could at least talk, I'm working 2pm to midnight shifts but I should be off fri evening and all of saturday.

Hey, John/Blue, why don't you get out of the damp NW and come down to AZ and visit the Desert Datsuns group, would love to meet you and share info/stories and adventures!

so i ran it without the belt and it still makes the whirring sound - easier to pick it out with no fan noise.

the pitch of the sound follows revs and it's got me mighty worried.

the whole thing started after i did a high-rev shift from 1st to 2nd and i definitely felt an "event" in the engine - not any kind of horrific clunk or anything, but definitely something that made me think "wtf just happened??" then the alternator issues ensued, so i figured the alt blew up and that was that.

sounds to me like it's coming from the mid/back of the engine bay - could it be clutch related? oddly, the car seems to be down on power - kind of feels a little wheezy/breathless. doesn't really feel like the clutch is slipping though...

i took this video to capture the sound - don't watch, just listen (you'll get seasick as i move the phone all around the engine bay to try and pinpoint where it's coming from)

Edited April 25, 201411 yr by rossiz

also - i tried using my handy-dandy new mechanic's stethoscope, and while it's cool to listen to the injectors clicking, the valve train and whatnot, i couldn't seem to get any reading on the whirring sound. tried all over the engine, front to back, including the clutch bell housing, nothing conclusive.

i have a new water pump coming ($30, easy job, prob. not a bad idea to do that anyways)

Hmmmm... Very odd...

So I'm trying to think of what parts of the engine have either ball bearings or gears. I'm coming up with the timing chain assembly, the oil pump, and the distributor... and not much else. Maybe touch your stethoscope to the oil pump?

Or perhaps your water pump (yes, I know, front of engine) has some bent or broken vanes.