Heater core leaking
I’ve followed these steps, up to where I disconnect the pipes into the core, which has worked quite well….

http://www.brazeauracing.com/rangerover/heater/index.html

Now just waiting for a recommendation for a heater core replacement that will not have me redoing this again.

Anyone got a suggestion?

I took the dash out and did the Audi core method on mine. Sorted the heater box flap shafts at same time.

I did replace mine with (I think) Audi. I’m not sure it was a good choice. Our Canadian winters are cold and it is marginal for heat at -30C. I didn’t remove the dash, I did the mod where you cut and resplice a brace.

I fitted the Allmakes one (https://www.lrdirect.com/stc3261-heater-matrix-new-rr) to a clients car and it appeared to be OEM from the markings moulded into it. But it isn't something that Britpart will have had made for them so I suspect it comes from the same factory just via Britpart and it does have a 2 year warranty. Not so good on a RHD car where the dash or steering column has to come out to change it but a fairly simple swap for you if it does fail.

I replaced the core and o-rings a couple of years ago - was either Allmakes or Britpart, somewhere I'll have a record of it. The o-rings started dripping again a week or two ago, replaced them yesterday - had a look at the 'end' of the cassette where the core slides in (RHD & only took out dash and ducts, so not a good going over but more of a check for any obvious leaks) and it seems to still be OK. Last time I had the heater box out of it.

Will find out after a proper run, it's 80% back together for now. It could be my lack of practice with o-ring replacement but it seems from that one sample that the cheaper core might be able to outlast them - and as both need at least most of the dash out to me that indicates there's not a huge benefit to getting an expensive version.

If I were totally confident that I can fit o-rings left right and centre then I'd probably get the Audi/equivalent core and do it. I don't mind the dash coming out except for the fact that most of it falls apart a bit more each time.

I replaced the O rings when I first got my car nearly 13 years ago and they are still fine. I will only ever use genuine LR O rings, at £3 each it isn't worth saving a few pence on aftermarket, but getting them seated properly is the most important part of the job. Getting them in place and then giving the pipes a wiggle to make sure they have seated fully before doing the screw up fully. What causes them to leak, other than old age, is heaving on the pipes where they go through the bulkhead if you are trying to get the underbonnet hoses off.

Gilbertd wrote:

getting them seated properly is the most important part of the job. Getting them in place and then giving the pipes a wiggle to make sure they have seated fully before doing the screw up fully.

That's really useful advice, I think the mistake I made the last time was to assume the clamp being tight was more important when it's actually the rings and seating of the pipes that does the bulk of the work.

If you actually look how it seals, the clamp doesn't clamp the pipes to the heater core, it allows movement that is taken up by the flexibility of the O rings. It's a flexible joint of sorts, admittedly one without much movement, but it can flex a little. The screw only needs to be done up tight enough to hold it in place, doing it up too tight is likely to crack the matrix and then it never will seal. The flexibility is why I always use genuine O rings too, you've no clue how long generic O rings will last before going hard.

What causes them to leak, other than old age, is heaving on the pipes where they go through the bulkhead if you are trying to get the underbonnet hoses off.

I soon need to address the hoses as they look awful and 'seeping' coolant (plus I want to reroute the LPG reducer) and to minimize the 'stress' on the pipes by simply - and carefully - cutting away the hoses' ends with a sharp knife. Will see....

That is what I normally do. the only time those hoses need to come off is when you intend replacing them, so I just slit them lengthwise with a Stanley knife and peel them off. To fit the new ones, a smear of silicone grease makes them slide on easily.

Changed heater core and O rings last week. Also changed the temp sensor on top of engine as it was part of my fault finding as I chased the cause of rough idle beginning 10 seconds after warm engine start that lasted another 15 seconds before idling normally.
Heater core replacement was painlesss enough and agree re wiggling pipes as you tighten the screw. There ended up being another 2 x 360 degree turns of the Phillips screw after wiggling the pipes, this after me originally thinking that they were tight enough. Been a week and 200 miles, no leaks.
I do, however, have another issue which I can’t tell is related to my work or a common issue.
I burped the system as best I could after replacing the core. I ended up putting approx the same amount of anti freeze in as I took out.
Remembering that I have a brand new temp sensor installed, I now find that when I drive that the temp indicator in dash is sitting at 1/4 reading and not the 12 o’clock position that it was at prior to the new sensor changing. The gauge doesn’t move up or down during a drive but stays in same position as if 1/4 reading was the norm. Engine idles fine and no roughness.
Any ideas as to why this is happening?
My first thought was air in system but I’d imagine that this would cause a high temp rather than a low one. My next thought is that the temp sensor is calibrated differently.
Beyond that I haven’t a clue…..

Have you got any diagnostics? If you have, what temperature is it running at? GEMS tend to run in the mid 80s C while Thor run a little hotter around 92-95C.

My suspicion is that the new temp sensor is calibrated differently. I suppose you could confirm this by reinstalling the original sensor.

Sensor turned out to be faulty. False readings for everything had me chasing down rabbit holes. I swapped it out for a sensor from my “donor” P38 and all is right in the world.

What brand was it so we can avoid them in the future?