Had to leave for Hong Kong on a very short notice Monday last week.

Today came back to be greeted with a dead battery and a few drops of coolant on the underside of the subframe. Sure enough the level had dropped from max to almost min, which on the M62 isn't a lot of liquid but there has definitely been a leak. Could not see a puddle as I had parked in the yard and had the car covered.

I replaced the battery which was purchased early Feb 2020 and was only 90Ah with a 100Ah which was the best I could get my hands on at the moment. Granted this battery had seen the worst in the car, including an alternator failure, is 3 and a half years + change reasonable for the L322?

I topped up the coolant and had a very thorough look in the engine bay but couldn't locate the source. I haven't had any coolant loss ever since the top radiator hose wad replaced. Cats do like to nest in the engine bay though. So maybe it was them...I don't know.

Took the car for a drive, all looks normal...

I had an EGR thermostat leak on my TD6 very hard to spot but its the plastic thermostat on top on the EGR cooler at the front top of the engine. Just a thought.

Thanks. The closest thing to what you mention that I can imagine of is the coolant temp sensor which is new (last feb) and perhaps the quick couplings by the gearbox thermostat. I don't know how susceptible those could be to some cat maneuvering around the pipework...

Yes thats what i had to change on mine, but if your is new then shouldnt be the issue.
Sorry no further clue

A follow up on the subject matter. After nearly two months, I woke up to find again drops of coolant on my driveway. Raised the car to off road height and crawled underneath. There was a drop coming from the belt tensioner underneath the crankshaft pulley but nothing else visible.
Opening the bonnet and shining a torch sideways towards the water pump, I caught a droplet coming from the pump's seal against the block, swiftly dripping down without trace and resting on the cover's ridge around the crankshaft, behind the main pulley. The result is not exactly a puddle on the driveway, more like a smear of...dog pee but it's a problem nonetheless.
Tuesday she's in for a new pump and thermostat, for good measure. Would consider doing the 85C thermostat mod but I have no time to order and wait for the kit. Need the old girl up and running again asap.

Nothing is easy with my car, it seems...
The mechanic needed to strip down the entire front of the bloody engine just to get the damned water pump out-I have my 2nd thoughts on that-. That included the crankshaft pulley and every effing belt and pulley there is.
Been without the car since Tuesday and won't be having it back before Monday afternoon, at best. I have a trip to make and need to be on my way on Tuesday evening. But with the car untested and so many things that could go wrong after such an extensive teardown I have lost all trust. In fact it was with a heavy heart I sent it in for the pump in the first place, fully knowing that the cooling system and not only, would be messed with. But on the other hand, I don't take chances and always choose to keep up with maintenance instead.
What is frustrating, however, is that I can't help but feel like no amount of money can buy me proper service... Such a helpess feeling.
I've rented a VW T-Roc for my trip and put the FF up for sale...I'll have to let her go, for the right price. A shame, really, but if I am to be renting for such trips I've specifically purchased the FF for, then not much sense in owning it. I would cancel the trip just to make it right, say a week later, in the proper vehicle, but I sadly don't have this luxury.