My 2001 XK8 has been running the fans far more than it should & constantly loosing coolant despite no obvious leaks.

A thorough check of everything revealed that a jubilee clip on the distribution/crossover pipe in front of the thermostat housing had been overtightened, causing the plastic to crack. The hose attached to it had been pulled up to hide the damage but wasn't sealing completely.

As I took the hose off to inspect the pipe properly the cracks propagated along the pipe to the point where I had no intention of binding it up with duct tape or some similar bodge-job; a new pipe was needed.

Taking it off revealed a huge amount of limescale accumulated inside both the pipe & the hose; previous owner hadn't thought to use deionised water.

The point of the post is this:

Be VERY careful tightening up those clips

If you're loosing coolant this is a great place to start searching

Don't use hard water to top up your coolant.

RH