ACE pipes front replaced - check
ACE pipes rear replaced - check
ACE primed and up and running again - check
New rear coolant lines to the back heater fitted - check
oil change and filter - check
New front pads, rear caliper pistons and seals - check
brakes bled - check.

Fill up the coolant and get heat out of the rear heater? How the do you manage to do it?

I've double checked and am happy that I correctly plumbed up the new coolant lines so its not a case of wrong way round and hitting some sort of one-way-flow valve within the matrix. I've raised the header tank, bled the valves etc etc ...

but no rear heat.

any tips ? V8 or else ...

I was only reading about this a couple of hours ago. Seems to me you need to remove the rear wheel arch liner and disconnect pipes there. Of course I stand to be corrected 👍
And the pipes to the fuel cooler by what I can see. 2016 4.4 diesel

MD's fill the system with a vacuum tool. Just had my coolant changed due to replacement gasket and there was very little fuss involved. Simple drain and suck fill. No rear pipes or wheel arches out. 405 AB exec seats Baltic and Cirrus
93 RR Classic efi

Remember it's easier to get forgiveness than permission!

Gone in order:
4.4 TDV8 SE - gone to a good home
93 Classic hard dash Plymouth Blue
03 L322 Oslo Blue
2000 Disco TD5 ES Epsom Green
98 P38 Rioja Red
89 Classic Cairngorm Brown

Mmmm as said stood to be corrected. Seems I misunderstood the rear was for drainage and flushing. Sorry.
Why not download the wsm from the wiki all the information is there. Including how to bleed 2016 4.4 diesel

I’ll re-read the WSM and see how it goes. I cracked open one of the joins in the wheel arch and coolant came out … so the coolant is getting to there along one of the pipes. (I’m wondering whether there is a valve in the rear unit which is not letting the coolant flow through.

I think it would help if I knew which pipe was the flow and which was the return because then I could trace the coolant along and open up the return nearer the front end. V8 or else ...

So had another stab at it this morning. ( I'll add pics a little later )

No joy following the partial drain / refill process by the letter.

Had thought it may have been the diverter valve sat underneath the FBH, but on looking through all the workshop manual I ruled that out because the valve controls all cabin heat ( front and rear at the same time ), so if I was getting front heat, then the valve was working. Which led to the issue being the rear circuit.

So, took the sill tray off, and the air tank dropped to access the new pipes running under the sill. Disconnected a pipe and found coolant only draining from the engine side, and not the rear circuit side, so definitely a big air lock in the rear heater loop.

Made a couple of plugs to stop the engine side pipes using spare heater pipe and a 15mm copper end cap for house plumbing:

Click image to enlarge

Click image to enlarge

Sounds like a pain in the buttocks. I had issues with mine a couple of weeks ago. It’s cold in the rear,but the heaters work great front and rear passenger compartment. So as the pooch is always in the back it’s better for him for now.
Well done for sorting it out  2016 4.4 diesel

Just one of those things that you reach a point where you go sod it, I'll just have at it and accept I'm going to get wet. Much muttering was had thats for sure !

A little more hindsight, I think its a youtube vid which mentions that one of the pipes running to the rear has a restrictor with in it. I chopped my old pipes down and found it. Its a plastic restrictor which takes the bore down to about 6-7mm. I dont know if its in the flow or return pipe.

I now wonder if this creates some sort of differential in the pressure / flow rate between the pipes when filling, which means that one pipe of the loop fills faster on re-fill, and as a result the imbalance created will push out the air. Who knows ! ( who cares now )

Lastly, for future reference:

From looking at the WSM and the actual pipe work in the engine I think* that the flow return is as below: