mac wrote:Also Siôn, check that the soldered in connector stub pipe has not cracked where it is joined to the end tank - with age the soldered joint can fail and give the impression of the pipe not sealing.
Mac.
That's great advice, thank you, I had wondered whether that was a possibility. I will give it a close inspection. I did however realise today that the jubilee clip I was using was of very poor quality and was actually breaking as I tightened it. I'm going to find a better one and see if that makes a seal, otherwise I think the culprit may well be what you suggest - how do I repair that?
John - I'm not sure if the thermostat is actually faulty, I was just suggesting it as a possibility to explain the behaviour, but I'm not so sure any more that it's a problem.
Today, I have been doing a few more jobs. I greased the driver's window winder mechanism which was very stiff, but that hasn't really made much of a difference. I think the stiffness is due to the fairly crude nature of the winder, compared to an improved design in later years (although I don't have a photo of BHX's door to compare).
I also took my centre console apart to replace the bulb for the transmission selector gate.
I was half expecting to find some lovely bodgery akin to John's '78 model, but I was rather pleased not to find any. The only bodgery that I did find was the explanation of why the gate didn't light up - someone has fitted a rounded connector to the wire, whereas in fact the bottom of the bulb holder is a spade! A few snips with my electrical pliers made good work on that, and as a bonus, the existing bulb still worked.
I really like the way it lights up, it's much cleverer than in 1978 MY onwards where all the positions are lit up - the bulb holder moves along with the lever, so only lights up the position that is selected - neat!
Oh and this is the best shot I can manage of the crappy dashboard lighting:
Finally, I decided to investigate why there was no sound coming from the speakers - I know the radio itself is fine as it worked in BHX. I was expecting a loose wire at the speaker perhaps, but the problem was a little more fundamental than that, as behind the grille lies....

...absolutely nothing!
A few minutes on ebay has sourced me a set, so hopefully they will arrive during the week to be fitted next weekend.