the arrowed sensor is normally a blank plug so yes u can replace it
the middle is the temp gauge sender
the right hand one is the coolant temp sensor for the glow plugs.
id say the right hand sensor is a glow plug sensor someone fitted incase there other sensor packed it in...

 

Agree Mike. The hole that extra sensor is in usually has a little hose that connects to the rad filler neck - helps system bleeding, but on later models it was deleted. I wonder if a sensor would just screw in or would it need an adaptor ?

 

The hole that extra sensor is in usually has a little hose that connects to the rad filler neck

No - that hose is on the upper thermostat housing and is just visable in the top of the picture.

 

Didnt some models have 2 stage glow plug syStem

 

Mine has two stage glow sensor/timer and that is still blocked off.

Cheers.

 

i have no idea but i can throw around some guesses, my guess is high temp a/c cut out and/or a/c fan cut in when the coolant temp gets too hot

it also looks the same as the glow plug temp control ????

 

Cheers for the replies. Never been anything pluged in it, and no loose connections anywhere so i guess it's a random.

Motor was rebuilt about 80,000km ago (last owner) so maybe the water pump is 2nd hand or from another motor...

So, if i can get an a/m gauge with a sender that can fit here, it'll be the right place for temp reading...sweet.

Now i just need to know if i can do the same for oil pressure, or if i'll have to use factory position and loose the dash gauge...

 

there is another allen keyed plug looking from under the factory oil pressure sender in the housing