The cooling tower is the riser that comes up from the manifold to the thermostat housing. It is made of plastic and is a known problem for cracks. An aluminum replacement part is available (try google - "thermostat housing xj8") and costs about $78.00 online. It is a small PITA to change, but I am a rookie (and old and feeble) and I did it in about 1.5 hours. The factory method to change it probably involves removal of the intake manifold, but several of us have done it by buying or making an 8mm wrench and working out the 4 bolts. I would think an independent would do it for south of $225.00 including parts.

BTW, the other plastic ccoling piece, the crossover pipe on mine developed a pinhole, but an aluminum part is not yet available, so I relaced with OEM part. It took 15 minutes, and the part was $65.00 as I remember.

I believe that these partsd are attacked by using non-Jaguar coolant as i did, but I certainly don't know if that is the case. I undersytand that Dex-Cool is a good replacem,entfor Jag stuff and that is what I niow use.