Well, it was all too good to be true...After a few days trouble free with new top radiator hose, expansion cap and thermostat, she's back to spewing out coolant...
Symptoms have been insidious and would have been rather inconclusive without a thorough investigation and proper monitoring.
Residual system pressure does not remain overnight, at least not excessively, after short drives e.g. the 100 km daily commute to work. I could drive it daily to and from work and probably not even notice anything wrong. Even coolant level won't drop much, if at all.
While it is totally fine for short daily drive, when doing 150km+ runs, coolant will start overflowing. On cooling down, some noticeable residual pressure remains and expansion tank smells of gas upon opening.
There is no overheating whatsoever during everyday runs, at least not yet. But there is a hint of slightly elevated temperatures 111 C to 114 C while cruising after 300+ km.
Dropped her at the garage for gaskets, heads overhaul and timing chains, with VANOS to be decided whether in need of replacement or not. But as I am planning on holding on to her for quite a while, I am leaning towards replacing both units unless vetoed by the master mechanic.
Bill is hefty but albeit a tidy sum, it can't buy me a new car. Sure enough though can give back my own for another 225K km.
Barring a cracked block, I'm fixing her up nicely and sorting out a few more niggles while at it...

Will keep you posted

Again, thank you all for helping me out diagnosing this one and probably catching it before being too late.

Hard luck, you've been through the mill with this one....

Yes indeed. It's been an experience I could certainly do without. But on a positive note, I'd be doing this at some point and timing isn't too bad at the moment so hopefully I can strike this one out for good.
Car was purchased right, which leaves me with enough room to go the extra mile with maintenance. And looking back, I've put almost 55K km on the clock in 26months. She's held up pretty well so far in my book...

I would still have changed the thermostat again, before going 'all in'.

its only four bolts, and a refill.

I did change the stat.

Replace the vanos or reseal them which is a very easy job, I didn't do either on my recent rebuild as there was no previous vanos noise. I now have the vanos start up rattle so it's getting ripped apart again to reseal the vanos. I bought a 2nd hand unit have stripped it down and carried out a reseal was actually very easy todo.
Why oh why

That's the concern I expressed to the mechanic. I do at least 2-2,5K km a month. I'd hate to have it opened up for knackered VANOS like next year. So unless somehow vetoed (with rationale explained) I'm changing those right now. Ideally will source a BMW pair otherwise I'll pay full JLR sticker if that's what it takes.I don't really fancy it but I'll be thanking myself later...

Unfortunately the time has come to pull the plug on this project. A week apart gave me enough time to contemplate. As much as I like the car, this is such a major repair that I will never be able to trust it again afterwards. There are tons of things that can go wrong. And if I've learned something so far, is that there hasn't been a single job on it that I wasn't forced to tackle in more than one way and in more than one instance. I've therefore lost the feeling, it seems.
I'm still waiting on the verdict as to whether or not there is a catastrophic damage to the heads or block but as I said, I am not feeling well about all this and honestly don't care much anymore.
I will be literally flushing a ton of money down the toilet but cutting losses is never a bad move as I'm no gambler.
I'll pay up the garage in full compensation for their time and probably have it written off before the month's end. I would gladly put it out there for parts to whoever is in need but don't know how to actually make it work with laws and all; I guess EU forum members could somehow be benefitted but let me see how / if such an undertaking is a viable option at all.
Otherwise I will literally have to give it away to the scrap yard but I'll make damn sure no major part of it can be used, which is such a shame as the car is generally in great shape.

Steady mate


Try some steel seal, cost minimal and may well sort it out or allow to get rid at auction

The cylinder heads have already been dismantled and should be at the workshop at the moment. So the steel seal ship has sailed, I'm afraid... I'll drop by the garage tomorrow morning to have a look myself and chat with the mechanic.
Call me stupid but I turned down a decent offer a few weeks back as I wasn't 100% positive that HGs were okay and didn't want some poor guy stepping into this minefield.

If you've already stripped it then surely you'd be as well getting it back to full health and selling it then if you no longer have any trust in it? 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

Indeed this might be the right choice here. I'll see what best, in terms of due diligence, can be done to make sure it'll last reasonably well when I visit tomorrow.

Not an easy one, really.

Thanks for your thoughts.

Final decision made. Moving forward with the repair. I would forever regret for not trying, at the very least Will take a while to complete and I'm also sorting out some more niggles while at it.

Reverting

You know it makes sense  2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

If the head is already off then it’s just a case of reassembling it back in reverse. Hope they left the parts in order. 🤣

Hope it all works out. I tend to fit all new bolts, nuts, studs as well along the way together with all seals, gaskets and rings. The cost is barely anything compared to the labour cost involved, and I don’t like retensioning previously tensioned materials.