Hi I have recently posted threads where I have encountered in-cabin heater problems, the blower was working fine but no heat..... So I decided to Flush the Engine/Radiator cooling system, Flushed the Heater Core/Matrix, Replaced the Thermostat, Renewed the Antifreeze, Changed the Electric Auxiliary Coolant Pump and then "extensively" Bled the whole Cooling System to eliminate any Airlocks etc. The heating "problem" was eventually solved....but NOT, by any of the above..... So as a last resort.....I embarked on changing the Heater Flap Actuator on the fan blower motor, and as i started to remove the front fascia "heater control" panel, I noticed one of the connector was not properly inserted and had become loose, soon as it was connected....Hey Presto! ....we now had Heat .... Problem Solved !!!!..... But, I have now come across another quite "worrying" problem, The Top Radiator Hose becomes "FLAT" (collapses) when I rev the car up. I have never noticed this before, and wanted to know from you guys if this is normal?....to me it looks horrendous and "scary" to say the least, it is as though it is trying to "suck" water, but it is not getting anything and the effort of this suction is making the "round" pipe (top hose) go totally "FLAT" ????..... That is the reason why I have explained in detail of all the work I have carried out on the cooling system, and I thought maybe I have done something wrong, which is causing the top hose (pipe) to collapse when the car is revved.....can anyone shed any light on this problem ? PS. The replaced Thermostat was a brand new Febi make, with a new Sensor and a rubber Seal etc.