Dual electric fans?

[johnj92131]

I have been having a small cooling system issue for the last 6 to 8 months.  After a good freeway run to bring the truck up to normal operating, when I park the car, I notice a small loss of coolant coming out of the radiator overflow bottle.  Over time, this loss of coolant leads to a low coolant level in the radiator and I have to top it off.

 

What I think is going on:  After the engine stops the coolant continues to get warmer from the heat soaked engine.  That leads to the coolant boiling off into the overflow tank and from there onto the ground.

 

The radiator is good quality and just over 18 months old.  Radiator cap is 4 months old.  My truck has A/C which means I have a second radiator fan that is supposed to come on with the a/c AND/OR when the coolant temperature hits 220.  The electric fan turns off at 200.

 

My VW Passat uses 2 electric fans to keep the engine cool.  But, when the engine is turned off, one of the fans continues to run until the coolant temperature stays below 200 and this means I don't loose coolant to an over flowing recovery tank.

 

This got me thinking about dual electric fans for the Comanche and an old article by Dino Savva (aka Cheromaniac on the JeepStrokers site):

 

http://www.angelfire.com/my/fan/electric.html

 

Is anyone here using dual electric radiator fans?  Think Don still might be, but is anyone else?  Link to Don's post on XJtalk:

 

http://www.xjtalk.com/showthread.php?t=13188

 

And Link to Don's article here in the DIY section:

 

http://comancheclub.com/topic/7895-dual-oem-aux-fan-installation/

 

Looking for input on this or similar modifications.

 

Edit:  Yes, I have also read the dual fan article on Go-Jeep's site.  He uses 2 Ford Taurus fans.

 

Thanks,

[DirtyComanche]

I won't comment on dual fans, other than to say I ran dual Taurus aux fans, it works if you want it to.

 

 

I will say I think you're chasing the wrong issue.  The cooling system is not behaving how it should, and I would suggest that you verify actual operating temperature by means other than the terribly inaccurate factory gauge.  Gut instinct is you have an issue with your tstat, water pump, or your overflow bottle is the incorrect one, cracked, or does not have the correct or a broken drawstraw in it.

[johnj92131]

Replacing water pump and T-stat today! 

 

Yes water pump was shot.  Will see what that does for me over the weekend.  Overflow bottle will have to be checked.  It is the same one in the truck for the near 10 years I have had the truck.  But who knows what previous owners did or did not do?

 

Agree that a proper, stock cooling system works great.

 

Thanks for the pointers!

 

JJ

[HOrnbrod]

Yep, agree with Dirty, your cooling system isn't working as it should. It looks like you're on the right track to fix it though.  :cheers:

 

As for my dual fans, they are still working great. I use the Spal PWM controller and depending on which temp sensor you use and which option you use to wire them it in, you can program the primary or secondary fan to shut off at an engine temperature of your choice after the ignition is turned off. I don't use this feature though - never had to. 

[johnj92131]

Appreciate the comments so far.  One more link to a dual electric fan set up below.  This one uses a BMW temp switch to turn the primary electric fan on and off.  Installation seems very simple (even I might be able to do it).  But it is a bit of a kluge fitting the temp switch.  Lastly, BMW parts are never inexpensive.  Same goes for any German parts.  Still could be much less expensive than the Spal controller.

 

http://www.naxja.org/forum/showthread.php?t=1035194

[Siopposition]

Only thing I have to say is that dual fans with a newer auxiliary fan will never....never ever pull as much air as a 7 blade mech fan and a zj fan clutch with the new 10 blade auxiliary fan next to it....

 

Sent from my SAMSUNG-SM-G891A using Tapatalk

[johnj92131]

Only thing I have to say is that dual fans with a newer auxiliary fan will never....never ever pull as much air as a 7 blade mech fan and a zj fan clutch with the new 10 blade auxiliary fan next to it....

 

Sent from my SAMSUNG-SM-G891A using Tapatalk

 

ZJ fan clutch???

I understand about the 10 blade aux fan.  But not how the ZJ fan clutch is different from the MJ/XJ fan clutch. Please explain.

[Siopposition]

I'll look up the part numbers tomorrow. But I believe 96-98 heavy duty (318 5.2) fan clutch pushes more cfm. The fan clutch from the zj bolts up and clears the radiator of the mj/xj and pulls much more air than stock or electric. Lemme find me readings tomorrow and I'll let u know. It's a good 40% more air.

 

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[Jeepman]

I have been running dual 10" 1200CFM fans for over 6 years now with NO issues and 2 of those years has been with my 4.7L stroker engine...

 

My setup is Dual 10" aftermarket fans Proform I think was the brand and Derale Adjustable NPT thermal switch mounted to a custom fan bracket

(ignore the Aluminum rad it was just for mock up)

 

I agree with others with it likely being other issues but see no reason why not to use electric fans...

[Rockfrog]

I'll look up the part numbers tomorrow. But I believe 96-98 heavy duty (318 5.2) fan clutch pushes more cfm. The fan clutch from the zj bolts up and clears the radiator of the mj/xj and pulls much more air than stock or electric. Lemme find me readings tomorrow and I'll let u know. It's a good 40% more air.

 

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The stock MJ/XJ clutch rotates at 60% of engine speed when locked. The ZJ/TJ clutch (Hayden 2737) rotates at 90% of engine speed when locked.

And that's how it pulls more air.

 

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[HOrnbrod]

Only thing I have to say is that dual fans with a newer auxiliary fan will never....never ever pull as much air as a 7 blade mech fan and a zj fan clutch with the new 10 blade auxiliary fan next to it....

 

Sent from my SAMSUNG-SM-G891A using Tapatalk

 

I take all this "never ever" with a grain of salt until I see some figures. A single 10-blade late model XJ fan pulls 1400 CFM @ 12VDC. These numbers were posted by a manufacturer of aftermarket aluminum radiator / three fan MJ/XJ kit over on NAXJA. Have to commend the guy for his honesty. He admitted the two stock fans pulled 200CFM more air than did his 3-fan setup, then quantified it by stating that the stock fans also pulled more amps under load.

 

And of course the 10-blade stock fans pulled more amps. More air CFM = more load = more amp draw. My fans are fused at 25A, same as the stockers. I've never had a problem with running hot in the 8+ years I've been running this setup and would never go back to the stock mechanical fan. With the Spal two-speed fan controller I get sufficient cooling with the primary fan only running at LO speed for about 75% of the year. The only time both fans run at HI speed is when stuck in heavy traffic in the hot summer.

[Eagle]

What year MJ and what engine?

[johnj92131]

Well my truck is still not out of the shop.  They had a couple of hot jobs that needed to get out and since I don't use the truck as my daily driver, I told them it was fine to let the Comanche sit and take care of their other customers.  Did stop by the shop this morning and look at the old thermostat.  It looked nice and clean but have not tested it's operation.  Did count the blades on both fans:  The mechanical fan has 7 blades and measure 15 inches in diameter.  The electric fan has 8 blades and looks like the original unit. 

The radiator cap is 13 lbs and only a few months old.  Is that the correct pressure rating for the 91 H.O. engine?

 

The shops guess is that the water pump weeping/leaking caused the over flow tank problem because the leaking water pump provided a means for air to get into the cooling system.  So there was no suction to suck the coolant in the overflow tank back into the radiator.  So I will just have to watch and see what happens as I use the truck over the next month or so.  Lastly, the shop tells me that the cooling system seems to be very much stock, meaning all the hoses and equipment seem to be as the factory intended.

 

Again, thanks to all who have helped.

[DirtyComanche]

A leaking water pump is a totally reasonable cause for this.

 

As you said, keep an eye on it.

[HOrnbrod]

I'll look up the part numbers tomorrow. But I believe 96-98 heavy duty (318 5.2) fan clutch pushes more cfm. The fan clutch from the zj bolts up and clears the radiator of the mj/xj and pulls much more air than stock or electric. Lemme find me readings tomorrow and I'll let u know. It's a good 40% more air.

 

Sent from my SAMSUNG-SM-G891A using Tapatalk

 

Let's see the "40% much more air" than stock or electric figures mate. :popcorn:

[Rockfrog]

Well, 30% is the actual number, based off the figures from Hayden's publishings. 60% of engine speed (stock XJ/MJ) against 90% engine speed for ZJ/TJ fan. So, 30% more fan speed ... as to how that equates to actual airflow ... dunno.

 

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[Knucklehead97]

Doesn't having dual electric fans help with horsepower and gas mileage due to not having to spin a big metal fan to pull air in? I'm sure it's a very slight increase, I just had heard it did help nonetheless

[HOrnbrod]

Doesn't having dual electric fans help with horsepower and gas mileage due to not having to spin a big metal fan to pull air in? I'm sure it's a very slight increase, I just had heard it did help nonetheless

 

It does remove some external load from the engine, but not enough that I noticed. I suppose it could be measured on a dyno.....

[Jeepman]

Electric fan conversions get better HP/fuel economy on a conventional style fan replacement but as the XJ/MJ fan is offset so the load is not the same on the engine so the numbers are better but not as good as say a CJ/YJ/TJ...

 

My customer feedback for CJ/YJ/TJ's has been on average an extra 50KM per tank of fuel (roughly an extra 30miles per tank) I have yet to get any real feedback on XJ/MJ's because most MJ/XJ customers don't do the conversion and when I did mine the first time I got maybe 15-20KM per tank with a 15G tank but with my stroker I did 100 things at the same time so I can not know when the increase is with my now larger 23G tank...

[A-man930]

I picked up a fan switch for a Volkswagen of some kind a while back that will thread into the stock Jeep radiator. It has two switch points in it that correspond pretty close to when our stock auxiliary fan comes on. I had hopes of setting up a dual electric fan arrangement. Have yet to try it :/

[johnj92131]

I picked up a fan switch for a Volkswagen of some kind a while back that will thread into the stock Jeep radiator. It has two switch points in it that correspond pretty close to when our stock auxiliary fan comes on. I had hopes of setting up a dual electric fan arrangement. Have yet to try it :/

 

A-man, interested in that switch...Any more specific information about what year/model VW it came from?

[A-man930]

 

 

I picked up a fan switch for a Volkswagen of some kind a while back that will thread into the stock Jeep radiator. It has two switch points in it that correspond pretty close to when our stock auxiliary fan comes on. I had hopes of setting up a dual electric fan arrangement. Have yet to try it :/

A-man, interested in that switch...Any more specific information about what year/model VW it came from?

I'll pull it out of the attic tomorrow. I found it the really, really long way (by thread pitch and temp switch points) using various online catalogs and then figured out what applications it fit then bought it. Now I'm really wanting to try it out.

[Big Dan]

_{This video could help}

 

_{https://www.youtube.com/watch?v=cGTLt5SJtB8}

[mikekaz1]

I have a factory electric fan and a aftermarket 10" instead of the clutch fan. I run consistently cooler all year with the full electric setup. Only issue I still have is with the plow in the fully raised position, temps still creep up to ~240. Unless I keep it slightly lowered.

[A-man930]

The switch was actually installed during my latest radiator change but I kept the box.  I have yet to get a connector for it, and the switch points are definitely an experiment, but we'll see.