Old thread I know, but can anyone tell me how on earth the durite mechanical temp gauge fits the 300tdi? The durite sender doesn’t even fit in the hole of the thermostat housing on the engine???

If you look at my earlier post it shows my Durite gauges.
The coolant temperature gauge is electrical and the supplied sensor screws straight into the 300TDi position and gives a perfect reading.
I did originally buy a mechanical Durite temperature gauge but decided not to fit it due to possible long-term problems with the capillary sensor (i.e. I wondered if it may become fragile with over time especially if it was removed & refitted from time to time). An adaptor is required to fit the sensor housing, I bought one off Ebay but sold it on along with the gauge.

Yes it’s the mechanical gauge I have got, do you have any idea where I can purchase the adapter? Searched everywhere

As I said, I bought mine off Ebay but it wasn't listed as for a 300TDi or anything like that, it was a generic adaptor and you have to choose the correct threads at each end. Bought it from a place that dealt with specialist parts (kit & classic cars etc).
Having had capillary gauges in the past I eventually decided against the Durite one hence why I sold it on and went electric (which as it turns out was a good choice). If ever you want to remove the instruments you have to undo the bulb from the housing (and loose some coolant) and then carefully feed the capillary tube through the bulkhead. I remember when I had a similar set-up on my 101FC (going back over 25yrs) I damaged the capillary and ended up fitting a civy spec temp gauge into the housing (luckily Series items were a direct swop).

I have a durite mechanical water temp gauge, been fitted almost 7 year.

vibrations have made it fail at the bit where it goes into the back of the gauge.

£30 for 7 years is not really an issue so I will get another but this time not have the capillary tube straight to the gauge but rather make a vibration loop behind the dash clocks