By on January 21, 2016


electric fan. shutterstock user Maksim Vivtsaruk

Robin writes:

Hi Sajeev,

Back with a topic that might be real to many Texans and others of warmer climes. I’m close to 220,000 miles on my 94 Nissan D21. She’s still motoring along and I’m doing my to keep her maintained.

We’ve just come through the dog days. Back when it was hitting 112° in Dallas, I was finding myself stuck in afternoon rush hour traffic on 75 and the coolant temp was pushing upwards into a zone that definitely had my attention. Fortunately, the traffic cleared and I could get back up to speeds that moved sufficient air across the radiator.

This experience prompted research and pondering: what about an aftermarket electric fan? When stopped in traffic, it would keep up while the engine was idling at low RPMs. And how many times have I stopped briefly to run in somewhere and returned to start up and see the temperature way up there from sitting still?

So, my research has yielded data on how to go about electric fan installation. My question is, would it be a worthwhile upgrade or just “putting a wing on it?”

Sajeev answers:

I think an electric fan conversion is a great upgrade for some people … but not for you.

Looks like an Altima fan swap is doable, but will its significant electrical draw burden your stock alternator? (Compare the amperage output vs. the donor Altima) And assuming your D21 is still factory stock, why go through all this effort?

Your problem lies with a (clogged) radiator, a (leaking) fan clutch, or both. Thankfully, both are easy to replace, unlike the Altima fan swap which requires more parts and far more labor. Run your hand behind the (not running!) fan clutch. If you feel oil and dirt, it’s gotta go. Start there first. Considering the mileage, replacing both of them isn’t a bad idea anyway.

I feel like I know you and your truck well by now, hence my conclusion: there’s no need to reinvent the wheel, just recondition it when needed. What say you, Best and Brightest?

[photo courtesy: Shutterstock user Maksim Vivtsaruk]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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33 Comments on “Piston Slap: Cool Thoughts on Electric Fan Conversions...”

  • avatar

    Just another thought – is the front of the radiator clogged with bugs and dirt? That’s an easy fix.

  • avatar

    Nice looking truck!

    • 0 avatar

      Very nice. Include shipping to the northeast and a vulpii might give you up to $30,000 for it.

    • 0 avatar
      Big Al from Oz

      I bought a new D21 King Cab in 1986. There were two variations of the D21, the global model and the Hardbody.

      The only Hardbody style we had in Australia was the King Cab. It also had a US suspension which made it more comfortable than the 1.2 tonne payload global Navaras.

      I only had one problem with mine, the gearbag sh!t itself at around 200 000km.

      They came with a lacklustre diesel as well. Initially the diesel were NA 2.5 litre engines. The diesels were bullet proof and ran 24/7.

      The D21 was the first ever pickup to win an industrial design award as well with Nissans graphite pads placed between the rear spring leaves and chassis design. The biggest drawback was the torsion bar suspension up front, which was a legacy from the orignal 520 series Datsun pickups.

  • avatar

    Agreed with Sajeev. No need for alterations to the way the cooling system was laid out from the factory, in a properly functioning state it should have no problems. Thankfully your trusty old D21 is both easy to work on and easy and cheap to get parts for!

    You can feel the radiator hoses and heater core hoses to try and get a feel for whether or not coolant is circulating well. A blocked radiator, broken water pump impeller, or not-fully opening thermostat could be the source of problems.

    Rock auto prices for KA24 equipped D21 radiators are a mere $60 on average ($110 for a nicer Koyo), $12 gets you a set of upper and lower rad hoses from Gates, $15 buys you a Gates water pump, $7.50 for a Gates thermostat, fan clutches run from $30-55. AutohausAZ has a genuine Shimahide fan clutch for $60. Gates is the OE supplier for hoses/belts/pulleys/pumps for most of the Japanese OEMs by the way, top notch stuff. All of the work could be done in about 2-3 hours, just be careful with ‘burping’ the system when you’re done!

    • 0 avatar

      I would agree. Replacing those parts is good maintenance at this point. You might be surprised at how well the cooling system works afterwards.

    • 0 avatar

      I suggest one of these funnels. I used one back when I was a Nissan tech, and I never had any trouble burping a D21. Plus, the assortment of fittings means you can use it on almost any car.

  • avatar

    Agreed, R&R is the easiest. Don’t forget to flush the entire system if you replace the radiator. Avoid using tap water and just get a bunch of distilled water and flush until several cycles produce clear water then refill the system with the proper coolant. I always recommend the 50/50 premix to save some hassle. Although depending on your AO and the weather you can run a different mix. If the weather doesn’t get too cold you can run more water and bump the overall ability of the system to transfer heat (on the Shelby I run a 30/70 mix of coolant and water plus something to break the surface tension as it doesn’t get that cold in my area typically).

  • avatar

    Probably time for a new fan clutch, make sure the fan blades are all straight and oriented properly, and then a coolant flush. It’s likely beyond its service life at that mileage.

    Kinda also goes without saying, but make sure you aren’t losing coolant somewhere through a leak or bad head gasket.

  • avatar

    Agreed , these trucks shouldn’t have cooling issues .

    Every try a citric acid flush ? it’s cheap and works amazingly well , cleans out everything and cannot damage the tinfoil think aluminum radiators used in old Hondas and Mazdas .

    On oldies , I’ve many times installed electric fans , mostly as pushers , they work *so* well I usually delete the stock fan , always use a relay and temp switch at one end or t’other of the upper radiator hose .

    Heat soak problems will *disappear* , I spent Decades in the Mojave Desert in my old 1949 Chevy Pickup with it’s 235 C.I. i6 engine , it never overheated , never , Death Valley fully loaded didn’t phase it and it only had a 35 ampere Delcotron alternator and a tiny group 26 battery….

    I always get a laugh out of those who failed 7th grade science class and try to insist that pusher fans don’t work as well as puller fans do…


    • 0 avatar

      whether blowing into or pulling through dense fins like a radiator, a fan design which can generate more “static pressure” is more important than whether it’s in front of or behind the heat exchanger.

    • 0 avatar

      It mostly depends on the seal between the fan and the radiatorat low speeds. Push/pull comes into play at high speeds when you need to factor in speed over air.

  • avatar

    Sajeev is right you likely just need to fix the existing system. When I was doing a lot of four wheeling I helped a friend with a old dodge and a toyota swap in electric fans for off road work. No upgrades to the alternator was needed on either one. My experience is the alternator are usually oversized enough for this but of course this varies.

  • avatar

    Check the fan clutch before anything. It can’t free-spin at all. If locked it’s done too.

  • avatar

    I approve of e fan conversions, ive done many on my jeep cherokees. The stock fan clutch is terrible and they overheat. Sometimes I’ll just add an aux fan to the side hooked up to a switch and other times I’ll eliminate the whole mech fan and run a ford Taurus or aftermarket electric fan set up. Frees up a couple ponies and greatly helps keep the jeeps cool when offroading or in slow traffic.

    • 0 avatar

      The difference this Nissan isn’t a junky XJ with a totally terrible cooling system from the factory :p

      I say that in jest of course, XJs are awesome rigs, but cooling system woes seem to be all too common of a problem!

    • 0 avatar

      I’ve got a ’02 Dakota and thought many times about doing a e-fan modification. Mainly because the stock fan is LOUD, like scary loud when you first start the vehicle or when it kicks in at idle. It’s been that way since new so nothing is wrong. I’ve got the towing package which includes a larger alternator so the extra load wouldn’t be a problem. Just makes sense to free up the engine from turning that one huge fan and instead run two smaller fans only when needed.

  • avatar
    Big Al from Oz

    I would replace the radiator and I would assume the thermostat has been changed out already.

    I used to a D21 King Cab and never had any issue with overheating. This is in the Australian climate. I used to load the bed and tow a trailer behind as well.

    Off road it never overheated, in the Australian summer.

    The only time I really see the need for electric fans is if engine mods have been made, especially for this vehicle.

    • 0 avatar
      Big Al from Oz

      Oh, or a re-core.

      I didn’t have a fan clutch, get rid of the clutch.

    • 0 avatar

      “…I would assume the thermostat has been changed out already.”

      I second this – make sure your thermostat is operating correctly. If you’re going to flush and fill, swap hoses, and/or swap the radiator, it’s probably worth it to install a new thermostat at the same time. Probably $15 in parts and you’re already in there, so there’s no reason to skip it. In a four-seasons climate, thermostat failure is much easier to notice, but in Dallas, the only symptom could be what you’re experiencing.

  • avatar

    Another vote for “fix what’s broke”; this is not a challenging situation for the factory cooling system, when in proper order. Could be a bunch of things, and lot of them won’t be fixed by swapping in an electric fan.

  • avatar

    If the overheating is just once in a blue moon, a free “fix” is turn off A/C and turn on heater full blast, if you haven’t already tried this. Otherwise fix what’s broke.

  • avatar

    Very cool truck! These guys covered everything already but I’d like to add a couple of ideas. Personally, I would only recommend an aftermarket fan setup if you were racing and wanted to free up every last bit of horsepower. Otherwise, leave it stock! An aftermarket electric fan may only serve to mask an existing problem.

    #1. Use compressed air to blow dirt and debris free from the radiator tube & fins.

    #2. The fan clutch, when cold, should have some resistance. The fan should not free wheel, if it does, R & R.

    #3. The thermostat could be sticking, if you decide to replace it, you can get one that opens at a lower temperature and is fail safe. 112 degrees is an insanely high ambient, I could not cope.

    #4. Many of my friends claim Redline “Water Wetter” works wonders. I have used it in the past but I didn’t have an issue to begin with so I can’t speak to its effectiveness.

    #5. Coolant in Texas need not be a 50/50 mix, try 60/40 as Raph suggested.

    #6. Replace the coolant temperature sensor while you’re at it, it’s cheap enough.

    #7. If #’s 1-6 fail, R & R water pump!

  • avatar

    I’ve definitely been disappointed with electric aftermarket fans that are sold for this, I had some I put just for auxilary cooling on the really hot days on a project car of mine (but still kept the belt fan) and it barely did anything to the temp. The whole thing was a waste and loud as hell.

    I then put a heavy duty aftermarket aluminum radiator from Summit and that REALLY dropped the temperature and it stayed there, even on the hottest days at a stop light.

    If you’re dead set on getting an aux fan, do some research and buy an OEM one from like a salvage yard, the ones that are sold at auto parts store just don’t move enough air.

  • avatar

    The mechanical fan is kicking in when it should? I didn’t think an electrical fan would pull much more air than that.

  • avatar

    Sajeev gives sage advice which should be followed… and then later an electric fan should be installed. Because you can. I mean think about it you’ve done 220, is 300 in your future? Assuming it could be done for reasonable cost I say go for it. Your stock alternator may already be getting tired along with the rad, why not a proactive upgrade after you rectify the problem at hand?

  • avatar

    Fan clutch and/or debris on or in the radiator is your problem.

  • avatar

    Thanks guys. Yes, the obvious is the place to start. Ought to be fun if nothing else.

  • avatar

    Sanjeev is correct. The conversion is a terrible idea for an otherwise bombproof factory cooling system.

    The d21 forums love the electric conversion. I have no idea why. The factory system has sufficient capacity and is generally been very durable. If you have the VG motor, you need to stay on top of timing belt changes. If overdue, swap out the water pump while you are in there because the labor is redundant. Assuming that the timing belt has been replaced on schedule and the water pump was replaced at that time, then you need to see if your thermostat is opening. This is an easy check.

    Start it up. Open radiator cap. Let it warm up, look in top of radiator and see if water is circulating. Then shut it off- the heat should have contracted the fan clutch and it should be difficult to turn the fan by hand. If you have no circulation, you need a water pump or a thermostat or both. If you have circulation but the fan spins freely by hand when the engine is off and hot, then you need a fan clutch.

    And this all assumes that you have done the obvious: radiator is topped up and clean.

    With 200k miles, it is likely a combination of factors. Weak can clutch, lazy thermostat, and maybe a failing water pump.

    New radiators from Rock Auto are cheaper than a radiator re-core. Actually, all of the parts I listed are really inexpensive for the d21 from Rock Auto.


  • avatar

    Thanks a lot. Now I’m going to obsess over an electric fan for weeks.

    Owned one of these (87 model) for years. 350k miles. Three engines but never a water system failure. Miss it now that it’s gone.

    Seems like an electric pusher fan was designed for economy as much as anything. Mine never seems to turn on for most of my driving. Can’t really see a drawback if your electric system is healthy.

  • avatar

    aw man, the first truck that I purchased with a loan was a used ’94 Nissan hardbody. I loved, loved that truck even with the gutless 4cyl. They’ve all rusted out here in Michigan.

    But still, I got a lot of work out of that truck and only sold it because it was an awful family vehicles, baby seat ‘n’ all.

  • avatar

    My own experience with going electric on my four-cylinder YJ Wrangler, was nothing but positive.

    Removing the stock fan took off the weight of the fan and clutch and let me remove the eighteen-inch funnel-like fan shroud. This opened up the engine bay (spaced for a six; the four was pushed back against the firewall) and made other maintenance a snap.

    Engine was quieter, in and out, idling or running. And the fan was needed…almost never. I had an override switch on the dash I could click on if I was in traffic, or on a logging trail, or otherwise going to be moving under 25 for long periods. Otherwise, forward motion brought all the air through there that I needed.

    That said…if this truck is overheating in traffic when it never did before, something has changed. Bug-plug of the radiator; or fan clutch…or…wait for this…a head gasket leaking. Engine running hotter is an early sign.

    Check those out; and instead of buying a fan clutch, I’d look into going electric.

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