Jose, I must admit I am reluctant to mess with it, as it is running well. A full engine recon is probably best if it needs it.

Back to the bottom hose, I just realised that Chucks comments would apply to the American LHD model with the single large hose. In the UK version we have two small hoses, with an Alu adaptor in between, so I dont know if a spring is normally fitted. But the larger of the two hoses is quite flexible, so I think it could collapse under suction conditions.