Fan cowl size xjs

Has anyone put in a smaller fan cowl.
The person at the place I took my radiator to for roding and cleaning suggested if the size of the fan cowl was reduced to the exact size of the radiator core and I installed a 400mm or 16 inch fan and a 250mm or 10 inch fan it would be more effective in the hot summers here temperatures around 40 degrees centigrade.
Being smaller than the origional cowl it should also be much easier to remove if I needed access to anything.
I would be using the same fixing points just intend to alter the brackets to suit
Any thoughts pros or cons

When I replaced my mechanical fan with a 16 in electric fan I made up a o.9mm thick gal iron insert to exactly accomodate the new fan. It simply fitted inside the old cowl and riveted on.
I can’t say how effective this aided the cooling as I did a lot of other things at the same time. I will say the cooling system has coped well in our Australian summers… 40c +

There is something seriously wrong with majority of XJS owners, especially those having real pleasure of riding v12 version… Anxiety, traumatic events, bigotry - you name it.

Instead of changing the fan, cowl, coolant and re-inventing the wheel - why don’t you inplement start/stop system during the idle or valve operation suspending device - it would be so much easier :wink:

Apart from that it is worth mentioning that your best coolant doesn’t run through the water pump.
Just exchange your crap-like oil cooler to something much bigger (16rows with similar length…

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A well maintained original cooling system is absolutely adequate in all conditions, including 40° Southern France summers with A/C on and stuck in traffic.

And especially a full flow oil cooling system. It would be the best cooling modification worthwhile the money and effort.

The problem for me is that the mechanical systems of pulleys, belts, thermostatic clutch, exploding fan etc. require more attention than a basic electric set up. Just less to go wrong, fewer things to keep checking on.

After considering all the pros and cons I have decided to go down the electric fan route using one 16" fan and one 8" fan together having a total 3600 CFM. I read somewhere for a 5 litre motor you need a min of 2800 CFM.

I intend using two Mishimotor fan controllors one for each fan. The controllers are rated 25 amps and the two fans draw a total of 25 amps to close for comfort for me to use just one.

With the 12 volt supply to the controllers do I need to run wire back to the battery or is there some place under the bonnet I can connect to.The problem I can see with running the wires back to the barttery is the distance might be to far for the 10 gauge wire which is on the supply side of the controller

I would also like have manual switches for the fans somewhere inside if possible

Any comments good and bad would apreciated as you can probably guess from my posts my auto electrical knowledge is very basic


Best place to tap in is the power buss that goes along the firewall (engine side); looks like a battery cable that ends with an insulated stud at each end. It is just below the cowl screen lip, nuts are 5/16 Whitworth and covered with a rubber cap. Disconnect the battery before you mess with it…you will have to add some type of overload protection, preferably close to the buss as the buss is directly connected to the battery.

Maybe you should also consider the fact that your alternator might not have 25 spare amps to give…
Especially at idle, at night with lights on, and maybe in the rain with wipers, fans and rear screen heater on…? The 75 amps Alt in the older cars definitely doesn’t.

I have located the power buss thanks Robert and Aristides with regards to the alternator I’m lucky to have one of the 115 amp alternators on my car got to get lucky sometimes

My first car was a 1959 Ford Popular (not the sit up and beg type, more lie down and whimper). I upgraded the headlamps from 45W to 60W halogens and fitted electric wipers instead of the vacuum operated ones. On that dark and stormy night, lights on, heater fan on, wipers on, I managed to travel a couple of hundred miles, and was within 2 miles from home, before the whole electrical system packed up completely. Ditched the dynamo for an alternator pretty soon after.

Back in the day, if you left the wipers and accessories off, a car would run nearly forever on the battery. The ignition circuit takes almost no power. So one day the alternator belt broke on my XJ-S, I saw the warning light come on and looked under the hood and confirmed the problem. I was only a few miles from home, no problem. Barely made it. I forgot this was an EFI car, and the EFI takes a lot of current, draws down a battery in short order if the alternator isn’t working.

After reading the xjs bible and the fact that the B bank runs hottest would it be of any benefit to change the fans around and have the larger fan on the left and the smaller one on the right just wondering

It’s a parallel flow radiator so it will not make any difference what so ever.
The suggestion I followed from the book was to put a restriction on the A bank outlet. The theory is to try to equalise backpressures as the B bank flow is more restricted due to all the back and forth inside the radiator. Don’t know if it does anything good, but it hasn’t done any harm.

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Yeah, I had the same result. My restrictor was a 1/2" ID flat washer, which admittedly isn’t very restrictive, but honestly couldn’t see any difference whatsoever. Car ran fine, stayed cool. Of course, I didn’t have one of those nifty IR thermometers; it would have been interesting to take some before and after readings with one of those.

Another not so good idea bites the dust and may be another silly question instead of fiddling around with the sensors in the thermostat housing drilling out and retaping could you install in sensors hoses leading to the radiator and disconnect the ones in the housing?

You could, but in-hose sensors are infamous for causing leaks.

Thanks for all the help I’m just trying to get all the information together before I decide which way to go.I am also intending to install the filters in the top hoses and there might not be enough room for the filters and the sensors I think i will get another top hose install the filter and see if there is enough room for the sensor