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curious about Taurus fan swap for my 91 XJ


 
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ehall
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Joined: 21 Jul 2007

PostPosted: Sun Nov 25, 2007 5:25 pm    Post subject: curious about Taurus fan swap for my 91 XJ Reply with quote

I got to looking at something under the hood of this beater XJ and noticed that the top of the main fan shroud is missing. Rather than replace the shroud, however, I'm considering the Taurus fan swap.

This XJ has the over-sized radiator and a tranny cooler (automatic) behind the grill. Obviously it's got the electric fan already and it's just the clutch fan that I'm thinking about here.

It's kind of hard to tell from all the pages out there just how hard this actually is. The ZJ fan swap page here makes it look really simple, but that leaves out a lot of commentary (is it all manual? where is the temperature hookup?), and from the sideways mounting it looks like he only has one fan, and anyway that's a ZJ which I'm guessing has a little more room in the bay. Other write-ups make it look like a serious job involving hacking off bits of the engine, which I must say I'm not at all interested in.

So, how hard is it really? I would like to have the Taurus fan in place of the clutch fan without making major mods (I don't mind making a strap or something but I'm not even going to remove the clutch pulley much less do anything beyond that). I'd also like to have it use the existing fan-control circuitry, although I may wire up a ground switch so that I can flip it between auto and off. I'm not actually worried about cooling too much, since the existing radiators should be plenty, and a replacement housing and/or pump should pick up whatever remaining slack I need.

Thanks
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DavidXJ
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Joined: 07 Sep 2006
Location: Visalia, CA

PostPosted: Mon Nov 26, 2007 7:53 am    Post subject: Reply with quote

Any fan swap like this is going to be complicated. The problem with the 4.0L fan swap is that the block is so long. If you the fan and clutch but leave the fan idler pully in place, you only have roughly 3.5" to 4" to work with from the radiator to the front of the pully (I don't remember the exact measurement). Unfortunately, that's where the motor for most fans resides, and are usually at least 4" thick. This is why most people that do a fan swap talk about removing the idler pully and the nose of the idler pully bracket. The picture of that ZJ had way more room than my 4.0L XJ (I'm guessing its a V8 and they are a bit shorter?). The guys at GoJeep did this Taurus fan swap, but had already removed the idler pully and nose for a previous after-market fan swap. On that note, the electric fan I put in is starting to having bad-bearing sounds, so I am going to put a Taurus fan in its place. If the fan motor is in a different location and I can put the idler pully back in I am going to do this, because with the pully gone, I have not been totally happy with the belt routing and the loss of belt-wrap on the crank. I have been getting weird vibrations lately whenever the AC pump engages, but my mechanic says there is nothing wrong with the pump.

As to the wiring, it is not too difficult to wire up a relay to run this fan... it's finding a place for another temperature sender that's a hassle. You could use the signal from the stock temperature sender and ECM, but then your fan won't come on until over 225 degrees, or, it will come on and off with the AC. Even with a larger radiator, better water pump, a cowl hood, and a high-flow thermostat housing, the cooling system has a hard time keeping up with the 4.0L. So if your fan doesn't come on until 225 degrees, it will be constantly running too warm unless you are going freeway speeds (or it's freezing outside). You could then just use an overide switch to turn the fan on manually, but that's just a pain in the a##. Not that a manually overide switch isn't a good idea, but I'd hate to have to remember to turn it on and off all the time.

So in my opinion, because of the tight spaces at the front of the 4.0L Cherokee and the high temperature rating of the stock temperature sender, this is not just a simple "single-afternoon" swap.
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ehall
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Joined: 21 Jul 2007

PostPosted: Mon Nov 26, 2007 8:36 am    Post subject: Reply with quote

Banging out an aluminum shroud should be pretty straightforward, and if the Taurus fan can be removed from its plastic shroud (and can be attached to the aluminum) then that might allow for moving it around enough to avoid the pulley. That's only a couple of hours work, assuming that it's possible and straightforward.

A low-temp thermostat and/or sender could make the fan come on at lower temperatures. Looking at the electric fan notes from the FSM (see this post), it sounds like it might even be possible. It would probably be better to hook up a secondary sensor switch though--anybody know what temperature the clutch fan is supposed to engage at? If that's possible and straightforward (lol) then it's only a couple of hours work too.

I think a three-pole switch would still be helpful here. You could have one pole for HIGH that simply fed 12v straight to the fan, one pole for AUTO that turned off the 12V, and the last pole for OFF that turned off ground. That is only a couple of hours work too, not counting the time required to run the switch into the cabin.

I guess all told it's about a day's worth of work, maybe two days. A new shroud would certainly be easier.
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DavidXJ
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Joined: 07 Sep 2006
Location: Visalia, CA

PostPosted: Mon Nov 26, 2007 12:46 pm    Post subject: Reply with quote

I agree that if you could make a new shroud so that you can fit a Taurus fan without eliminating the idler pulley it would be better. Like I said before, I am not totally happy with the loss of belt wrap on my crank (after removing the idler pulley to gain space). At first it was fine, but lately I have not been happy with it. In order to eliminate the squeels under acceleration, the belt has to be tight like a guitar string, and due to this the AC pump seems to cause a low vibration when engaged.

But I don't think the lower temperature thermostat is going to make the fan come on at a lower temperature (at least in a 1998+). All the thermostat does is tell the computer what temperature the engine is running at. The computer then tells the fan to come on if it senses temps above 225. But if you could re-program the computer... yah right.

I like the idea of a 3-pole switch where one of the positions leaves the fan in auto, but the you can manually turn it on or off.

I exaggerated how hard it is to install a seperate fan thermostat switch. If you have the moeny to buy a fan control kit from Summit Racing (SUM-890015) for $50 (or other similar kits), you can put the thermostat in the supply side heater hose. The kit comes with a thermostat, relay, circuit breaker, and wiring. You can make your own splice out of plumbing parts to install the thermostat switch in... you just have to somehow hook up a ground wire to this since the switch needs to be grounded (or you can purchase it from a place like Summit Racing #ATM-2280 for $40). But with a little electrical knowledge, you could procure all these parts from a junkyard and plumbing store for much less than the price of these kits. I used a painless kit, and if your care, you can check out my write up here. http://www.cardomain.com/ride/2523112/4.

If you do find a way to mount a Taurus fan without removing the idler fan pulley, please post it here as a reply so I can check it out.
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ehall
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Joined: 21 Jul 2007

PostPosted: Thu Nov 29, 2007 6:08 pm    Post subject: Reply with quote

Thought about this a little more. I believe the Taurs fans have separate low and high speed connectors although I'm not 100% sure on that. If so it might make sense to replace both the clutch fan and secondary fan with Taurus units.

Then use a secondary sensor switch to tun them both on low speed, and use the OEM switch to drive both of them on high speed.

If I'm going to make an aluminum shroud it's just as easy (maybe easier) to make one to hold both fans.
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DavidXJ
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Joined: 07 Sep 2006
Location: Visalia, CA

PostPosted: Sun Dec 02, 2007 5:07 pm    Post subject: Reply with quote

I don't think you will have room to put a Taurus fan on the driver's side, because the power steering box only allows for a fan of about 12" diameter max. But if I am wrong and you make it work, I would like to see it.
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