check if working thermostat in astra diesel?

what would the symptoms be when checking a thermostat in an astra diesel when the temp shows half the header tank is very hot but the electric fan dosent come on also the water pipes dont feel hot does this sound like acar thats been tampered with or is this normal with a y reg asra with the isuzu engine
mr marlow, June 2005
it would be mour the thermostast because the engine will be hot and the pipes will be cold. so stic a new 1 in and bleed the system and thats it done.

karl, April 2007
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