Sidevalve engine temperature gauge

[Mr Spigot]

I am looking to fit a temperature gauge to my 918 MM engine and the obvious place to fit the sender is the plug for the heater tap on the cylinder head, as my car does not have a heater. Does anyone know what the thread size is and where I can get an adaptor? Is it the same size as the A Series ones?

[oliver90owner]

Hi, it may seem obvious to you but I wouldn’t put it there.

[Mr Spigot]

Why not and what is your alternative?

[oliver90owner]

No particular reason other than measuring the temperature around, or at about, the highest point in the system. Alternatives might depend on what you have available as alternatives and possibly the type of transducer used.

[liammonty]

I think you'll find that depending on which point you choose to fit the sensor at, you'll get a big variation in readings, as if you've got no heater, I presume you've got no water pump on your engine either. I suspect that the gauge will be useful in terms of indicating what's 'normal' rather than it running at a certain level if that makes sense. I can't think of anywhere else obvious to fit it and that point is high in the head, but I imagine the water flow will be really slow at the back of the head without it being pumped, so I suspect the reading will be quite high!

[Mick Lynch]

The heater connection is directly above cylinder 4 and as mentioned circulation (even pumped) is not the best there so could give an artificially high reading.

If you were brave you could drill and tap a sensor point in the neck prior to the thermostat (pumped) it’s a 1/2” BSP thread for period NOS but could be metric if you are using a modern aftermarket part.

Off topic but my pre series Morris Minor measures the temperature of the air in the air gap between the water and the filler AND it’s visible at all times from the drivers seat!

[philthehill]

You could always fit a temp gauge take off into the top hose using a kit of the type in the photo below.

Period temp take off.jpg (234.52 KiB) Viewed 163 times

Or even the types listed below
https://www.ebay.co.uk/itm/226051860527 ... BM3Lu-yN9j
https://www.ebay.co.uk/itm/395173389337 ... TH013MZPFT

[Mr Spigot]

Thanks for all the helpful suggestions. I appreciate that the heater take-off plug is probably the hottest area of the coolant and will give a high reading, but the aim is to ensure a consistent reading, so any change would indicate a possible problem. I like the period take-off adaptor which would retain an element of authenticity, as the car is quite original and unmolested. I shall keep an eye out for one.