Firstly apologies for the rather haphazard way of adding the images, one even being upside down even, but at my great age, these things don't come easy (or so the song says).
So why add a water temperature gauge? Well I feared that the engine was getting too hot and I doubted the efficiency of the fan sensor and the cylinder head temperature sensor.
So before I began with the gauge, I fitted a new radiator as the bottom of the old one was pretty rotten.
Then I fitted a new fan sensor. Still after allowing the engine to tick over for twenty minutes, the fan refused to come on. Out with my tester and I found that one of the feed wires for the fan sensor was rigid. When I stripped back the insulation, I found the copper wire was jet black, so I replaced this 18" length of wire with new and got the fan to come on. But I still had my doubts as the fan still proved temperamental and sometimes failed to come on every time.
The cylinder head temperature sensor. Renown for being 'iffy', the red light sometimes came on especially after a trip on the motorway at 70mph followed by stop-start traffic. Also the red warning light flickered rather than staying lit. I cleaned it up but that made no difference.
I should say at this point that the radiator fan should come on at 85c, followed by the red warning light at 115c, after which serious problems might/will occur - failed cylinder head gasket warped cylinder head, failed cylinder liner seals.
Time to fit a water temperature gauge so I could actually SEE what the hell was happening.
Image 4. Water Temperature Gauge from eBay = about £7. This came with a temperature sensor. Now where to fit it?
Image 2. The is an existing plug (at least on my R4GTL) on the water pump. Undo this using a 10mm Allen key. The threaded female hole has an M18x1.5 thread and for the sensor to fit, I bought a brass water temp gauge adaptor from eBay (£6.99) - M18x1.5 to 1/8NPT. Don't forget to use a decent copper crush washer twixt adaptor and water pump.
Image 3. I gave some thought as to where to mount the gauge as I wanted it to be in my eye line but neither stuck up on top of the dash nor pinching too much of storage shelving. So I chose to place it alongside the instrument binnacle. I drilled a couple of holes at the side and fitted a pair of M5 rivnuts. These are threaded 'rivets' and expand in the holes. I had to fit a small block of wood with a pair of M5x50 screws, to bring the gauge out to the right so it wasn't obscured by the steering wheels. Ikea meets Renault.
Image 1. There were three terminals on the back of the gauge - S = signal wire (to sender), + = ignition switch, - = earth. The two thin wires, black and red, are for the internal lights which I have chosen not to connect as the internal light is apparently much too bright.
All wiring was in 5amp wire with 5amp heat shrink crimped connector, wonderful things unlike their non-heat shrink counterparts. For the ignition switch, I undid the plastic steering column surround and found a connecting block close to the ignition switch. Rather than splice into one of the wires (the cream coloured one) I found a 5amp bullet connector made a nice push fit into the block.
So all wired up, ignition on, and the needle of the temperature gauge gave a nice twitch. Off on a test drive to see a friend four miles away, and I watched the needle climb, and climb and climb. 85c reached and no apparent sound of the fan coming on, 100c reached (a bead of sweat runs down my forehead) then 110c, before I arrive home. The system was properly bled yesterday with the expansion tank raised to it's highest point, the heater was in the 'On' position, the radiator topped up and the top hose 'massaged' to eliminate any trapped bubbles. No unwanted bubbles or smells coming from the expansion tank.
A puzzle, and I'm running out of ideas.