Rover Celeste Coolant Loss!

My 1999 Rover Celeste is losing coolant. Over a long trip the loss is minimal but on short (5 miles one-way) trips the loss is significant. The mechanic who usually takes care of my car says he’s pressure-checked it and can’t find the leak/loss. I’ve even thought of dumping one of those cans of fix-a-leak into the radiator but wanted to ask my questions first.

Second question, same vehicle: The rear parking sensors are currently out of service and I get the 7-second tone that means there’s a problem. When it went out it came back into function for 1-2 days, then out, then in for a few hours and now it’s out for good. Is there a cable or fuse that needs replacing?

Thanks for your help! (Rover alone isn’t on your list; just Land Rover and models)

More than once I’ve seen a water pump leak intermittently.
Start the motor cold and watch closely for drips as it warms up.

Did your mechanic check the coolant for evidence of hydrocarbons?
Did your mechanic try a UV sensive dye to find the leak?
And, as Circuitsmith said, a water pump can leak at the shaft seal only when the shaft is turning. This won’t always show up on a standard pressure test. The UV dye would, however, show it.

I’m not at all familiar with these backing systems, but your owner’s manual should tel you if there’s a fuse.