Looking at the engine from the front on the right hand side there is a Black plastic elbow bolted to the block with a hose attached.
Sitting in the top of the elbow are a Blue and a Black sendor each of which has a plug attached to it.
To remove the plug you need to depress the metal clip and pull it off.
The Black sendor does the gauge, it is held in place with a metal horseshoe clip.
There is a rubber O ring to seal it.
Buy the sendor, the O ring and another horseshoe clip as you will probably drop the old clip and lose it in the depths of the engine bay.
The clip pulls out of its slot (self explanatory when you see it) sideways, have the new sendor ready fitted with its O ring and lubed with a bit of washing up liquid, remove clip, pull up old sendor, discard it, position new sendor in hole, hold in place with one hand and re-fit clip with other.
Re-connect plug, top up coolant and you should be good to go.
Only do this when engine is cold.
I could send you a photo but unfortunately I sold the car to Gibby as you know.
Cheers
Nick
