Excessive brake pedal travel

Hi all , my wifes 440 1.6i has just developed excessive brake pedal travel ,the brakes work but this is puzzling me.She says it has just happened as though its component failure as opposed to a gradual deteriation. Have checked the fluid reservoir and all is ok. Any ideas as what to check please ?:)

pedal travel 

Check the self adjusting mechanisam on the rear brake shoes if this is not working the shoes will back off from the drums causing a lot of pedal travel.

Thanks but it is'nt that. Just took it out myself and i can lock up the front wheels no problem in an emmergency stop just the excessive pedal travel thats worrying me. Any ideas anyone.:)

Have another look at your back brakes. Ease the rubber boot back off the wheel cylinder and look for the start of a leak. I had the same problem and replaced both rear cylinders. They should be about a tenner each at any motorist centre. Check the auto adjusters are working while you have got the drums off. If there are no signs of fluid leaking put the drums back on and put the handbrake on 1 or 2 clicks and apply the footbrake and see if you have less travel. If so overhaul the adjusters. Hope this helps. It sorted my 440 TDi