Thanks for the nice diagram Philip. I was about to post the same thing as you but you beat me to it. Mine would be slightly different in only one detail, so I have cut and pasted yours to make an updated version.
Chose the capacitor value such that you get ~2 seconds or more delay on the second fan - that should make sure the fuses don’t blow if they are still commoned rather than split as in your diagram. That way, the old loom can be reused.
kind regards
Marek
His fuse will still blow, just not as fast. Even with the delay, he ends up with 28A on a 25A fuse. The simple solution s to go back to the stock fans and call it a day.
Thank you for your thoughts, much appreciated.
Mark
Mark,
This is the Fluke meter I use for current measurement, an oldie but a goodie…I see that Michael Frank has provided the fan part number details.
Fantastic, thank you so much for sending this over. Age doesn’t matter, it’s all about performance! I’m on the case.
Mark
Hi Mike,
I noticed an article “Jaguar E-Type Alternator Wiring Explained” on this post. Could you post this article, after I complete the AC I’m into the alternator function. Thanks.
Mark
Google pulled it right up -
Rob Y
I’m not sure why that banner comes up that way, I must have an error someplace. Anyway, Rob provided the correct link for the alternator article. It’s primarily about Lucas 11AC alternators, but Butec is similar in principal.
Hi Rob,
Great, thanks so much for sending this over.
Mark
Very good, thanks. I ran the Jag for 30 minutes with both fans on, no overheating with the needle reading in the middle of “normal.” Now I’m completing the restoration of the OEM cowl frame holding the fans, replacing the fans and all rubber, and replacing those aftermarket fans for a future project. Thanks Mike for everything, very much appreciated. Onward and upward.
Mark
FWIW that cowl is really needed to get the correct cooling effect. Also, when driving (fast) the foam in top if the radiator is also needed as otherwise too much air will pass the radiator.
I have original radiator on an unmodified, unrestored European spec 1972 car. 238HP at the rear wheels at 5.800rpm, 35 deg total advance. No A/C, no air pump, no smog gear, no problems.
The only issue with cooling was in Switzerland in 2018 when the other fan motor had run out of brushes, 46 years after the car was made. I took the fan home, put in new brushes, adjusted the free play, lubricated the bearings and put it back.
The temperature when running warm stays at +90-95C from idle to 229km/h.
According to the ROM the end of the water rail on the LH side where the vacuum switch is mounted should be +106C degrees so the vacuum retard for the ignition is fully closed. If not, or if it’s no longer working, that will retard your ignition up to 8 degrees which would make it run too hot.
The original design was done so the engine would get to the right operating temperature (rather hot) and stay there in all conditions. It will not run as well if it stays too cool.
Cheers!
Pekka, I don’t know what the definition is of “not run as well”…
Mine now has 74ºC thermostats, runs just below or on the N in the hottest of South African summers with AC on, has vacuum advance on the distributor (with full manifold vacuum) and a 68-72ºC fan switch. It is happy, happy, happy! It even starts MUCH quicker now in heat soaked situations. Even my wife has noticed (she asked me if I fitted a different starter because hot starts are so much better now).
My Chev C10 with 5.7L V8 also runs with 74ºC thermostat, on or just below 80ºC on the VDO gauge with matching sender. Having a viscous fan clutch, it will sometimes go up to 95ºC before the clutch engages and then it rapidly comes back down to 80ºC. I don’t like this though. Tempted to fit electric fan to prevent those temp spikes.
Hi Philip,
Exactly that. The engineers have designed the engine so that everything (cooling, lubrication, carburration, etc.) should run optimally at a certain temperature. That is why the thermostats, fans, cooling channels and capacity as well as the oil capacity and flow, have all been defined so that it would run as good as possible.
Once you start changing things there may be unwanted results, most typical being the mentioned vacuum valve not closing the distributor vacuum retard. Most people advice to just block it, but there are always other things that will be affected as well.
I am very happy with all Jaguar engines that I have even been using, but they are all different and factory specs for things like thermostats should not be forgotten.
Cooler is not always better, the AJV8 for instance had an optimal cooling fluid temperature beyond 100°C IIRC.
Sure, on the Series 1 70°C is good, but if you drive up a mountain or very fast, it’s normal that it will rise to 90°-95°C, that’s not “overheating”.
In my experience most real overheating that may result in valve seats dropping and other catastrophies happens when the car stands still and does not get enough cooling to the heads. The “Old school” advice for all high performance cars always works IMO, after a spirited drive or after taking the speedo to three digit speeds always run for a while in top gear with low revs and after stopping allow the engine to run for a while, or shut it down for just 1 minute and then restart for a while until the temps in the heads are reasonable.
The “Normal” operating temperature for the V12 is higher than on the XK engine (1949-1971) the later Series 3 XJ6 with EFI is another story again, for different reasons.
I would not change anything to lower the normal operating temperature of our V12 E-type, getting it to run at 70°C instead or 90°C would surely not do anything good, but it might change things for the worse. Mr. Claude Baily, Harry Mundy and Walter Hasan were no novices in 1971 when it came to engine design, they knew for sure what they were doing.
Just watch this: https://www.youtube.com/watch?v=u6h8PFaz-F8
Cheers!
HI Philip,
That’s really good, but like you write, you live in a hot climate, and there are things to consider, I bet it was hard to get a hot start with a serious heat soak, even here i the summer if you shut it off hot with the bonnet closed and fans stop as soon as power is off, yes, it will be a hard start as modern fuel also vaporises much easier than fuel did back in 1972.
Cold start is really easy though, 
Cheers!
Hi Pekka,
If I have gleaned one thing from the forum it is that the car functions best when using the original equipment, providing the equipment is in excellent condition. One of our E-Types lives in Las Vegas, and endures extreme temperatures; hence I felt the aluminum radiator was essential, particularly when running the AC. I am now convinced the OEM fans would have been just fine. The true toll of desert heat is evident on battery life; we replace the battery every two years.
Many thanks for your excellent commentary.
Mark
