1971 Datsun 521 Heartbreaker

[Matt H]

I finally got around to getting the radiator fixed. I forgot to take pictures before I put it back in - but I found a guy who was able to remove the paint, locate the leak, re solder / reinforce with tin plating and repaint all for 200 bucks which I thought was a pretty fair price. It looks way better and finally stopped leaking...

The truck hasn't been run for a couple of months. I've recently hooked up a trickle charger to keep the battery in good shape but noticed when I started the truck up the alternator was making a slight whirring noise. I'm curious if this sounds like its on its way out or not? I only had it replace a couple of years ago. I also noticed the running lights are twinkling ever so slightly (Hard to capture on camera). The noise speeds up when I put the headlights on etc.

Car idling:
https://i.imgur.com/3P4R8wA.mp4

Car idling with full beams on:

https://i.imgur.com/cshY66g.mp4

Running lights:
https://i.imgur.com/HeP3xbI.mp4

 

 

[banzai510(hainz)]

alternators are lame these days from Vatozone and Orileys. Even NAPA sucks I bet.

run this in your truck and you can tell when the alternator is stressed and then not chargin and you better be heading home.  When the IGN light is ON its too late. I run a version of this in my 521 and I trust it. Doesnt drain the battery either. less than a clock

many version some even cheaper

https://www.amazon.com/Battery-Charging-Condition-Alternator-Display/dp/B07422ZPT4/ref=asc_df_B07422ZPT4?tag=bingshoppinga-20&linkCode=df0&hvadid=80470559180558&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=67772&hvtargid=pla-4584070138333923&psc=1

[Matt H]

Thanks @banzai510(hainz) You just reminded me I had a multimeter in the tool box. I just checked the reading and i'm getting 12.73 with the car off and but its fluctuating around 14.7 and 15.07 with the car running. Is that normal?

Its also making a weird noise again

Here is the reader with the car running
https://i.imgur.com/WngAJVP.mp4

This is the sound its making
https://i.imgur.com/bCuJ4rn.mp4

 

I don't know if this is related but i've just done a load of sanding in the garage if that makes a difference as everything is caped in saw dust!  

 

Edited June 22, 2025 by Matt H

[banzai510(hainz)]

to me if thats at idle its over charging and will cook the battery.

I think its the volt reg. Alot of those suck also. Depends where its made. I had some from NAPA Echlin Brand I think. Didnt make it a year was like 15volts. 16/17 when driving.

at least you know your alternator works

 

I wiill assume you have a external volt reg and the stock alternator. for a 521.

 

I cant mind read everything but soemtimes a Newer Internal volt reg alternator gets installed and fight the external one. so up to you to know.

Edited June 22, 2025 by banzai510(hainz)

[datzenmike]

IIRC most owners that put an internally regulated alternator into a Datsun with an external regulator the engine won't shut off.

[Matt H]

Hey @banzai510(hainz) / @datzenmike It's a newer modern alternator with an internal regulator. The external regular on my truck has been bypassed. I'll check the plug into the alternator in the morning but from what you're saying it either a loose connection into the alternator or a faulty internal regulator. Maybe thats the noise I can hear and its on its way out

[ggzilla]

15v is too high. Which mean the voltage regulator is bad

 

When a diode has blown, it causes a faint whirring sound in the alternator

[Matt H]

Hey guys,

I'm in the process of switching out the alternator. I'm using a Bosch Remanufactured Alternator AL338X which is what the shop switched it out to a couple of years back. I have bolts all loosened but have little to no space to remove it. Do I need to pull the radiator out in order to get the alternator out?

[datzenmike]

Disconnect one of the battery cables first. Don't learn this the hard way.

 

 

AL338X is 90a internally regulated and for a mid '80s Maxima. That's a snug fit in a 521. 

 

You may have to drain the rad and remove the hose end from the timing cover and bend it out of the way, but it should come out

[Matt H]

OK cool thanks @datzenmike. Glad it wasn't just me as I tried every possible way to maneuver it out. Yeah the previous owner installed a bluetooth pre amp in the cab so I think it needs a stronger alternator.

 

[Matt H]

Hey @datzenmike So it looks like I need to switch over the alternator pulley. Is there a special trick to do this or do I need like an impact wrench?

 

[datzenmike]

Impact wrench should do it. 

 

I've changed one of these by just using a ratchet and quickly hitting it with the palm of my hand relying on inertia to hold the pulley in place.

[datzenmike]

It's the main amplifier that draws the power. I fit a 2002 Altima 100 amp to my 710. The heater fan is a tornado now when stopped at the lights and the turn signals no longer slow down nor do they make the headlights dim off and on. Belt needs to be tight when charging or it can slip and squeal.

 

At 100% efficiency 100 amps is just under 2 hp to drive the alternator. I don't know what the efficiency of an alternator is, higher than the old '50s generators, but going to be over 2 hp through that belt and why they went to the serpentine.

[Matt H]

Hey @datzenmike So I ran out and picked up a cheap impact wrench which did the job immediately. (Amazing how easy it was with the right tools) Now however the actually pulley on the old alternator seems to be stuck in place. Is there a trick to get these off or do I need another tool? I've given it a few knocks with a rubber mallet and tried some dw40 but its not wanting to come loose.

 

[datzenmike]

The original V pulley is from the 521??? so it has to have been put on there. Try a puller.

[Matt H]

Hey @datzenmike yeah its the original pulley. I managed to pry it off and now have it on the new alternator. I read I need to torque it to around 70 lbs? How do I torque it if its moving? Do you just used the impact driver or do I need to clamp it in a vice or something?

[datzenmike]

A vice should work.

[Matt H]

Am I missing something here? The shaft and pulley spin independently so even I'm able to grip the pulley its still going to turn when I try and torque it?

https://i.imgur.com/bZFeYMW.mp4

 

 

 

 

 

 

 

[ggzilla]

Bosch AL338X is a remanufactured Nissan/Hitachi alternator

 

There should be an allen keyway in the shaft. Use an allen wrench to hold it, while you tighten the nut with a combo wrench (or an open-end extension on your torque wrench)

2 hours ago, Matt H said:

Am I missing something here? The shaft and pulley spin independently so even I'm able to grip the pulley its still going to turn when I try and torque it?

https://i.imgur.com/bZFeYMW.mp4

 

[Matt H]

Hey @ggzilla  / @datzenmike There was no keyway in this alternator. Just a circular dimple with nothing to grip onto. I ended up just hitting it with the impact wrench as I felt like I was going to do more damage than good trying to get it into a vice. Its ridiculous how tight a fit this alternator is. You have to be a contortionist to get the belt back on and fit your hands in their to tighten up the bolts let alone trying get any tools down there.

I did however manage to dip my head in a full pan of coolant and engine oil like some sort of ratsun baptism which was nice.

Needless to say its now reassembled. Decided to change the lower rad hose for good measure. Are you supposed torque the bolts that connect the alternator to the frame or can you just do it by feel? Its not the most accessible with a torque wrench.

 

[ggzilla]

I've never used a torque wrench on an alternator. The bolts that fasten it to the fixed bracket are low stress. The bolt that fastens it to the adjuster bar is more critical, but still not a lot of torque is needed. It's not a very big bolt, so don't tighten it too much

2 hours ago, Matt H said:

Are you supposed torque the bolts that connect the alternator to the frame or can you just do it by feel? Its not the most accessible with a torque wrench.

[datzenmike]

Try reaching the bolts from underneath. The stock alternator is small like the 620 truck. There is little room to begin with with the radiator hose above and the grease fitting for the idler arm just below it. At one time I had a 50/60 amp car alternator on my 620 and the belt had to go on the pulley first then the two bolts for the mount. If a longer belt was used the alternator would swing down onto the idler arm.

[Matt H]

Hey @datzenmike I've just fired it up and burped the radiator etc. I feel like the alternator its a little louder than before (Maybe like a bit of a whirring noise) but i'm getting a steady 14.47 off the battery.

Alternator noise
https://i.imgur.com/QoCsARn.mp4

Is it normal for me to be getting some white smoke and water coming out of the exhaust? It hasn't been fired up for a few weeks but i'm noticing the smoke and water is pretty consistent. Please see below video

Smoke / Water from exhaust 
https://i.imgur.com/vYlKslV.mp4

 

 

 

[datzenmike]

I guess you have a warranty? sounds not bad, drive it and see if it blows up or not, then get a replacement.

 

 

As slightly cooler weather moves in the exhaust naturally condenses inside the cold exhaust pipe. Take for a 20 min. drive and it will likely go away. That much water would run the radiator low in a few hours, so check the radiator level for a few days when engine cold. I don't think there's anything to worry about. 

[Matt H]

Yeah I just took it for a few laps around the block and the smoke / water went away which is a relief. Will check the coolant levels in the morning. Maybe the alternator is ok - i'm just paranoid about any small noise now haha

I guess thats job done - well until something else inevitably breaks. Thanks both for your help 🫡