hi all,i have a 2001 tdi alhambra with heating and engine cooling issues,a few months ago i stopped getting heat through the heater,upon inspection of the radiator i diagnosed a faulty thermostat as the rad and thermostat housing hose to rad were stone cold!! having replaced the thermostat for a genuine vw part,it still isnt opening and closing properly,ive bled the system now on numerous occasions and wen stationary i can get the stat to open and the rad is red hot and heat coming from both heaters,but wen going for a drive it goes stone cold and the stat wont open. ive had a sniff test done on the system today to see if the head gasket has failed but came back clear,also it appears that there is sufficent water coming back to the expansion tank to think it cant be the water pump,im at a loss to what it could be!!! also as well wen going for a drive at motorway speeds its ok for about 20 mins but then the temp rises to almost 130 degrees!!! can any of you guys help??????