My 2002 passat 2.0-litre 8 valve petrol froze up due to lack of anti freeze. I let the car thaw but when started it has no heat and built up pressure very quick. I stripped out the water pump to find it had broke the plastic fins at back of water pump so I managed to get the big bits out but the fins seem to have disappeared and I can not see or feel them. Would they have broke up or will they do damage when I rebuild it?