Cooling system
The original radiator from the car was in good shape, and even had the outlets in the right place for the AJ6 engine. If I was building a manual car I’d have just used that and be done with it all.
But my car is an automatic, so I need a way to cool the gearbox. With the 4.2 XK this would be done via a separate ATF cooler between the radiator and the engine, which is basically a sleeve containing ATF around a main coolant pipe. Using this would require me to adapt the ATF hoses from the ZF4HP22, which I didn’t love.
I decided to use the XJ40 radiator that came with the AJ6, which has an integrated transmission cooler. Plus it’s a nice, light, and modern design to which all coolant and ATF lines would simply hook up correctly.
The only issue is size. This AJ6 radiator is about 15mm higher than the original (because it’s an early version, late XJ40/X300 rads are higher still) so it would require some modification to fit. The car’s bottom radiator support is a welded box profile which adds quite a bit of rigidity to the front end, so I wanted to keep that intact as much as possible. Unlike the owner of the XJC that the AJ6 came out, who appears to have cut the mounting holes with an axe.
So I modified the top radiator support, which simply bolts in but still adds rigidity.
I wanted a factory look, so I decided to modify an early 2.8 version by welding in a folded steel box to allow for the bigger radiator. Incidentally the modification added quite a bit of strength to the panel.
And here it is all painted and mounted up. You can see the AJ6 radiator is less wide than the XK one, so I’ll probably fill the voids on either side to direct the airflow and aid in cooling. I’m also using the XJ40 expansion tank for now.
From the rear you can see how much slimmer the new radiator is. I used the original mounting tabs with some sound insulation foam to keep everything in place and rattle free.
To finish off the cooling system I had to find a solution for the heater. The Series 1 XJ has the heater core connection right in the centerline of the car, whereas the AJ6 has the heater hoses offset to the left. I soldered up copper link pipes to make up the difference and painted them with heat resistant paint. I wasn’t 100% sure about the ability of a soldered joint to work in the heat of an engine bay, but since hot rodders have been using this solution for decades I’m willing to take the chance.
The original radiator from the car was in good shape, and even had the outlets in the right place for the AJ6 engine. If I was building a manual car I’d have just used that and be done with it all.
But my car is an automatic, so I need a way to cool the gearbox. With the 4.2 XK this would be done via a separate ATF cooler between the radiator and the engine, which is basically a sleeve containing ATF around a main coolant pipe. Using this would require me to adapt the ATF hoses from the ZF4HP22, which I didn’t love.
I decided to use the XJ40 radiator that came with the AJ6, which has an integrated transmission cooler. Plus it’s a nice, light, and modern design to which all coolant and ATF lines would simply hook up correctly.
The only issue is size. This AJ6 radiator is about 15mm higher than the original (because it’s an early version, late XJ40/X300 rads are higher still) so it would require some modification to fit. The car’s bottom radiator support is a welded box profile which adds quite a bit of rigidity to the front end, so I wanted to keep that intact as much as possible. Unlike the owner of the XJC that the AJ6 came out, who appears to have cut the mounting holes with an axe.
So I modified the top radiator support, which simply bolts in but still adds rigidity.
I wanted a factory look, so I decided to modify an early 2.8 version by welding in a folded steel box to allow for the bigger radiator. Incidentally the modification added quite a bit of strength to the panel.
And here it is all painted and mounted up. You can see the AJ6 radiator is less wide than the XK one, so I’ll probably fill the voids on either side to direct the airflow and aid in cooling. I’m also using the XJ40 expansion tank for now.
From the rear you can see how much slimmer the new radiator is. I used the original mounting tabs with some sound insulation foam to keep everything in place and rattle free.
To finish off the cooling system I had to find a solution for the heater. The Series 1 XJ has the heater core connection right in the centerline of the car, whereas the AJ6 has the heater hoses offset to the left. I soldered up copper link pipes to make up the difference and painted them with heat resistant paint. I wasn’t 100% sure about the ability of a soldered joint to work in the heat of an engine bay, but since hot rodders have been using this solution for decades I’m willing to take the chance.