Thor V8.

How is it done?!

RAVE says remove drive belt tensioner (easy, done), unplug connector (tricky but done) then remove the sensor.

I can't find any way to get any kind of tool on it!

There's no room for a spanner and I can't get a socket on it. Long sockets hit the bracket the tensioner mounts to and short sockets don't go on. Even if I could get a socket on there doesn't look to be room to get the ratchet on.

I'd like to avoid removing the oil filter or the water pump hose if possible. I'm connecting up an oil pressure gauge so it all needs rebuilding again to test and will need dismantling again to refit the switch.

The GEMS is far easier IIRC..

I used a Crows foot socket, with an unusal combo of extensions and UJ's on my Thor..

Can you remember what size socket?

I think I might just suck it up and take the water pump hose off. I think I should be able to get a spanner on it then.

Unfortunately that depends on the sensor fitted, I remember when going to replace mine with a new one that the new sensor had a different Hex size to the one that was fitted. I don't remember it being particually difficult to find something to fit it though. Turned out on mine that the reason it was going to be replaced (leaking) was down to the previous owner not managing to do it up tightly enough.

Can't remember what I used at the time to do it up though, it may have been a stubby (short) spanner or a socket, 18mm comes to mind for some reason though.

18mm seems to ring a bell with me too..

Took the water pump hose off and just about managed to get a spanner on it. It was a 22mm in the end.

Then I found out that the oil pressure gauge set I bought from eBay because it specifically stated it included an M12x1.5 adapter didn't include an M12x1.5 adapter. None of the adapters were labelled so didn't know until I found none that fit.

Back on went the oil pressure switch and water pump hose, in went the battery and I started it up.

Ran it until the temp gauge was bang in the middle. No overheating but I think it needs a bit more bleeding - the LPG system never came up to temp. No leaks and, most importantly, no oil pressure warning light!

I'm not completely sure it's fixed as the temp gauge is for the coolant temp rather than the oil. There's a chance it might come back on when engine is out under load and temps increase a bit more.

Need fuel, tax and insurance next.

Uh, curiously I am planning to do the same, you sure there is space for the pressure gauge sender there? Or it needs a relocation hose?
How would you plan to wire both pressure sensor AND the OE pressure switch cable? Usually they use this "tee" arrangement I have been suggested couple weeks ago in here, which I have still not bought since I need to get all ordered and if I get the wrong ones can't return them ....

If you want to know what the oil pressure really is, use a capillary gauge rather than an electric one. It won't be affected by voltage, poor earths or anything like that. I've got an old Maserati with an oil pressure light and a capillary gauge, light flashes on as and when it feels like it (due to traditional Italian electrics) but the gauge always reads correctly. In fact, the only gauges that do read correctly all the time are the two that don't involve electricity, the oil pressure and turbo boost gauges.

This is a test gauge only, not a permanent one.

The plan was to check the pressure and make sure it's up to spec and put the stock sensor back in.

You'd need a T piece to run a permanent gauge as well as the sensor.

Thanks! And so you tell me what I need is a 12x1.5 thread (which is the one your temp gauge did not have).
I will start to look for parts for this new contraption I am planning ...

Is yours a Thor? I gather that the GEMS engines have a different oil pressure switch thread. I think it's 1/2 UNF.

Thor indeed that is why I was watching with particular interest.
I'll get started ordering parts and will photo how it goes (I need to change the belt anyway so will do all at once).