1.6 diesel engine cooling system

i was wouldnt if anyone could help me ive got a 1.6 diesel engine in my golf but it keeps trying to over heat? well the gauge says it is i was woulding if this could be the temp senders as there are 2 but there it only one being used this is the one which comes out of the head to the heating?

there are 2 yes ive disconected one so i can heat my glow plugs longer so she start better when hot..these senders cause no end of probs really..if u are gonna replace the temp sender one ...there are many different sorts so best to take the one with u when ordering..and also go genuine on this at your local large vw dealer who know there stuf..there is also a chap at lincoln rd pboro..milfield auto,s can help with his contact..as he deals with them alot..always werth putting a new thermostat in aswell..your probs looking at £20 all in all very easy to fit ..

chearrs maye thts pretty helpful ill give tht ago!