My coolest cat
George now has a system the factory would have been proud of
Ihad spent a lot of time and headspace sorting out my V12’s cooling system (see last issue), so now was the moment of truth. If all were to go well, the full stainless steel small-bore-piped extravaganza would work and be productionised to give that sought-after ‘enthusiastic-amateurdoing-his-absolute-best’ under-bonnet look.
An extensive test run proved that the modified system worked perfectly. For some reason the engine was quieter too, and because so many jubilee clipped joints, flexibles and banjo fittings had disappeared, any slight coolant-loss went with them. On an extended road test, air bled perfectly out of the revised cooling system up the slight incline from the radiator top to the expansion tank. Result!
Time for a tidy-up
Now to make it all look halfway decent. The spouted crosspipe was removed, greatly cleaning up the engine bay. Then a couple of metres of 6mm malleable stainless small-bore pipe to connect the radiator top to the header tank was purchased and painstakingly fitted along the inner wing with stainless P clips.
The main feed to the engine from the header tank by the bulkhead to the engine coolant system was tee’d into the heater return pipe which runs handily by the new expansion tank. This type of heater return/header tank connection was how Jaguar originally plumbed the system on early versions of the XJS V12.
Finally Unit 7 Creations made a superb ally atmospheric catch tank, all powder-coated in red with a satisfyingly solid knurled screw cap, to capture coolant expansion from the header tank. This fitted in the space previously occupied by the OEM header tank. The entire modification gives a cooling system that is simpler, better, cleaner, far more understandable and serviceable.
In principle it is identical to Jaguar’s own installation in the 1990 era XJ V12 saloons, where height and space are less restricted. I calculate that four hoses, one pressure cap, four pieces of hardware and countless copper washers and Jubilee clipped hose joins have been eliminated. The system is more easily understood, more easily filled, more accessible, bleeds better, and is more reliable as a result. It also has a significant Jaguar XJS V12 HE nerd discussion benefit!
Next job was to replace my two electric fans, as one had started to vibrate when warmed. I had in a long-faded past purchased two lovely SPAL fans and have been hoarding them ever since, so out they came. The top mountings are done, and the bottom ones are to be done tomorrow. Onwards!