I don't want to get the old cooling system ball rolling once again but the Bongo system seems to function "normally" with the 'stst closed. In that state the other end of the stat is open to allow the coolant to bypass the radiator and circulate in the myriad of hoses, pipes and matrices - being a diesel engine and more thermally efficient than a petrol, less heat is wasted to the cooling system, therefore the radiator isn't required at this operating stage.
Eventually when the system reaches a predetermind temperature, the thermostat opens and brings in the radiator system to allow further cooling in it's circuit.
I haven't had my thermostat out (never yet found a reason to disturb it) but I know after a severe climb up to over 2000 ft in less than 5 miles the bottom of the radiator was only cool to touch and the top hose was too hot to touch. I then ran the engine at 2500 rpm with the van stationary and eventually th 'stat opened and the botton hose became hot.
You can get the same situation when bleeding the system out. The recommended procedure is to run the engine at 2500 revs for around 5 minutes - and only then will the stat be forced to open and circulate the coolant to make the bottom hose too hot to touch.
Don't go off in the sulk vanmanerik - your input to these fora is too valuable!.........freedom of speech and all that
