The Original White Mechanical Fan on my 1990 XJS V12 was showing signs of Stress Cracking and since I was also intending to fit a New Re-Cored Radiator, I didn't want to take a chance that the Fan might suddenly shatter.

As in the event that it did so, it could not only damage the Bonnet/Hood but smash the Radiator in the process.

At first I was thinking of fitting a New Mechanical Fan but the only ones available, at least in the UK are the 'Black' ones and although I have heard they are stronger, I am non convinced.

As for one thing the 'Hub' on the 'Black Fan' is only one inch wide, as opposed to two inches wide on the Original OEM White ones and my White Fan has stood the Test of Time, having been on the Car for nearly 26 years.

So having thought it over, I decided to fit Electric Fans, 'I mean how hard can it be?'

The Answer is it's dead easy!

The difficult bit is in trying to decide on how to go about it.

So maybe this will inspire you to give it a go and either copy how I did it or else come up with something even better.

At which point I must mention and give thanks to 'Greg' and 'Grant' for helping to convince a non mechanic like myself, that it would not be as difficult as I thought it was going to be.

So First I needed a Couple of Fans and found a pair of Twin 12inch Fans from an XJ40 V12 which came off a 6 litre engine, although I didn't have any idea if they would be too big to go in the Car.

So I just shut my eyes and took a 'Punt'







The Fans Arrive Looking Good but how the hell do I fit them?





At least they fit on the Rad so that's a good start
I'm trial fitting these on an old Rad and doing a Trial set up by fitting them in my Scrap Car.





I've made a very simple Frame out of some Scrap Steel, with a couple of Angle Brackets to hang from the lugs that are on top of the Rad.

The Tubular 'thingy' underneath is an extra support I 'Migged' up to help support the Fans and the Clamps that are sticking out of them

Were the Clamps from the Battery Holder of my Scrap XJS.

These Clamps will hook over the Beam that is underneath the Radiator and pull the Fans onto the Matrix.

As they need to be as Close to this as possible.





The Fans are now on position, with the Brackets hooked over the lugs on the top of the Rad.




The Brackets are then sandwiched between the Rad and the Closing Panel.

Also note the Tubular support strut, which was pushed on to Two Plastic lugs that were already moulded into Fan Shroud.





The Fan now in position Trial fitted onto my Scrap Car and Scrap Rad.




Closing Panel Trial Fitted on Top of the Rad




The Fans are now fitted with the Closing Panel on Top.

The Brackets that are holding the Rad are Sandwiched between the Rad and the Closing Panel.




These Clips 'Ex Battery Clamps' go through holes drilled in the legs of the Tubular Support Struts and the Clip over the Beam under the Rad.

Where they can be adjusted to pull the Fans close to the Matrix.




The Unit Removed from the 'Scrap Car' already for Testing.


We have lift off!


Just got to wait for the New Rad to arrive and then with help from Greg and Grant, I can wire it up and see if it actually works!

Comments/Questions

What do you think of it so far.

Not bad for £30 and a few bits of Scrap.

 

Good fab work. Now you really need to worry about a shroud - without one all is for naught since the fans will pull air though the sides and air gaps (instead of though the radiator). I'd suggest getting the shroud that were fitted to the fans and adapting that.

Also, I'm sure you've thought about some rubber grommets and strips wherever you have metal to metal contact to reduce NVH.

 

I do not think he does, Warlock. Those fans have an excellent shroud already, and as OB has them tight to the rad, no chance of short circuiting the air. The only reason the OEM fans have a shroud is because they are "open bladed" propeller type fans. Most aftermarket fans have a protective ring round the blades (even though OB's are OEM XJ40 V12 fans) and they do not need a shroud either. But of course they must be very close to the rad fins. Also, the gap between the OEM mechanical fan and the shroud is not particularly small, as it has to allow for engine movement.



Now I realise there are deeply held views on rads in XJSs, so I will don my flameproof suit and boldly say that the foams round the rad edges are also a 100% waste of time. For these reasons:

1. At road speed there is a huge but invisible wave of air in front of the car's radiator.
2. There is by a factor of (I guess) at least 20 times more air built up in front of the rad at 40 MPh than can ever get through it.
3. I believe the limiting factors on air travel through the radiator (and thus cooling efficiency) in our cars are (a) the density of the rad stack and (b) the poor aerodynamically dirty airflow into the stack.
4. Therefore any air that escapes round the small gap between the rad and the bodywork will have precisely Zero effect on radiator efficiency, as the huge air "wave" trying to get through the rad stack will be hardly, if at all, affected by the presence of absence of the foams.
5. Finally, there may even be a benefit, as extra air gets into the engine bay and reduces under bonnet temperatures!

Greg

 

Hi

Thanks for the Comp on the 'Fab Work' only four bolts are holding the whole thing together but it seemed to take forever to come up with a 'simple solution.

Since Greg has got electric Fans which have proved very successful, I am inclined to agree with him about all things airflow.

Though its a very emotive subject with lots of different opinions which I respect.

There is only one way to find out for sure and that's to start her up and try it out.

Thank you for your input, which is appreciated.

 

Hi Greg

Many Thanks

I've tried to tick all the boxes and I do think you are right about the 'Fan Shroud' so can't wait to get the Rad and wire it up in accordance with Grant's Master Plan.

Then we can see if the Engine runs, after standing idle for 17 years!

 

Excellent work OB.

BTW did you know the ring around the fan blades, its primary purpose is to reduce the wash off the blade tip. Centrifugal force of a fan turning at high speed causes the air to fly off the blade tips. Adding the ring improves the efficiency of the fan.

 

Hi Warrjon

That's a massive compliment coming from someone like you and no I didn't have any idea about the purpose of the moulded Fan Shroud.

To tell the truth I didn't have a clue what I was doing, it just sort of happened as I put it together on the 'fly'

So cannot wait to get the Rad and try it out.

 

Great work OB.

We are about to do something very similar to our XJ12C using something like this........ https://www.summitracing.com/parts/sum-g4850/overview/

I am also on the fence about the need for a shroud....... the logic that if the fans are very close to the rad, you are good to go, makes sense to me.

How are you going to wire them ? I have a twin fan set up in my XJS and its wiring is pretty simple..... Fan 1 comes on with ignition power. Fan 2 is controlled by the existing temp switch that originally controlled the small stock electric fan. Doing it this way allowed me to keep the fan overun after shutdown feature that I think is really useful.

Will be watching this post closely to see how it turns out on the car.

 

Hi Sarc

Cheers!

I doubt if you would need a shroud with Fans as big as those but as for the Wiring I'm lucky enough to have Two Experts to help me: Greg and Grant.

And since I wouldn't have a clue, I will wire it up how they suggest which could well be very similar to the way you have done yours.

Keep watching this space.

 

Mine are wired the same as Sarc's.

You can use the existing electric fan wiring for one fan, but you will need to add a relay and fuse for the new fan. I used regular spade terminals and slid them into the bottom of the fuse box under the bonnet (LH side on my car) next to the original fan fuse, so I slide the fuse in. The relay I located on the LH front of the engine bay near the other relays, I had a spare on the bracket so purchased the appropriate automotive relay to fit the bracket. A horn relay 50amps will do the job, the higher the amp rating the better as the contacts are more heavy duty and will last longer. A 30amp will do the job

My fans draw quite a bit of current so I ran new power to the relay contacts (to power the fan) from the main power terminal on the firewall. Power to pick the relay is low current and you just need to find a power wire that comes on with the ignition.

Best wire to use in the engine bay GXL automotive wire, its Polyethylene insulated and will take the temps all day.

 

Hi Warrjon

Many Thanks

We are planning to use a 70 Amp Relay which is about £5 and I'll also make sure I've got the right wire and all kinds of Terminals ready for the big day.

 

Now what I would love to see: has anyone got any figures showing how much power is 'gained' after removing the fan? My older Volvo 740 was, with eletrical fans rather than viscous, a lot more nippy. But then again, 115 hp were produced, the fan ate at least 50% of the power

 

That's an interesting idea Daim, I never thought of that!

 

OB,

Well done, it looks good! I agree that with the in-built fan shroud really close to the rad core, it should work fine without an external shroud. I ran a similar setup on my old Range Rover with twin electric fans. I also agree with the suggestion to run one fan off ignition and one off the rad temp switch. You could also run a manual override switch for the second fan. Mount the relays nice and convenient on inner wing or near top panel of rad.

Looking forward to the next stage!

Paul

 

Hi Paul

Glad you like the set up and I really hope it works, when I have got it installed in my red car.

Though even now I haven't got a clue what made me want to go Electric, as this was really out of my Comfort Zone.

All I really had to do was have a bit more faith in those 'Black Fans' and bang one on but as going Electric seems to be trending on the XJS I think I felt I just had to give it a go.

Even though I am still in the dark about whatever advantages (or either disadvantages) there may be in doing so.

But at least with a Twin Fan Set-up, they are unlikely to both go at once and so you can rig something up on the fly, in order to get you home.

Although the one thing that I noticed when I rigged it up on my 'Scrapper' was that it instantly frees up acres of space.

Meaning if you had to, you could easily change a bottom hose by the side of the road but should I take the mechanical Fan Boss off or else just go and leave it where it is, as it really doesn't seem to be in the way.

As far as wiring it up is concerned, I found some heat proof cable in the Shed, which either says 85 or 8.5 which is obviously a measurement of some kind. (any ideas?)

But physically it looks about the same as that which was originally on the Fans.
although I've got some thicker Cable if that stuff isn't really up to the job.

 

question ,the fans will draw air thru inside the close to radiator circles,, but look how much of the rad. is not being cooled, out beyond the fan diameters!

thats a lot of uncooled radiator, agree at 40mph and up air would cool complete rad.

but what gets cooled when in traffic, or idling slowly?

i'd guess around 50% of coolant gets bypassed and stays hot!

i like fan shrouds!

qick pic of my GN Buick with large single fan and close fitting shroud.

 

Completely agree with this. Shrouds aren't just to prevent air recirculating. Shrouds distribute the drawn air across the entire radiator. Calculate the total area of the rad and subtract your twin fans area and you'll get the uncooled area. It'll be a large percentage. Add to that the jags non-standard rad internal layout and you compound the issue.

Buy or make a full shroud. No question.

 

Hi Ron

That's got me a bit worried, as with your engineering background, you know what you're talking about.

So I may have to consider making up a shroud of some kind.

 

Hi Jig Jag

Cheers, definitely food for thought on that one.

 

Do not know any figures, Daim, but I gained about 1 MPG as far as I could tell. Definitely more nippy as you say. Also, turn-in was better in the counter-rotation direction, definitely the case, even the Management noticed. Also much quieter.
Greg