long pedal, this has just happened to me on a hk wagon which i think has a different brake booster to a HX.---anyway i installed a new master cyclinder because brake fluid had been leeking out the back of the old one. when i cleaned the brake fluid off the front of the booster i removed the push rod to clean the seal. this is when the problem happened. there is a small rubber disc about the size of a 20 cent piece and 5mm thick it falls out of a pocket inside the booster. its called the (reaction disc) and unless you know its in there you wont know its dropped out.all it takes is the pushrod to move out a little bit and its gone. so i couldnt work why i had so much travel of the pedal,bleed the brakes 50 times and still same thing. only after looking inside an old booster and with hk manual as a reference did i work it out. so i borrowed the reaction disc out of the old booster and with a bit of sticky grease put it on the end of the pushrod and assembled it on the wagon,carefully.once the master cyclinder is bolted up it holds everything in place . the result was dramatic, excellent brakes.only thing is the original disc is still somewhere in the bottom of the booster .oh well .

Thanks guys, i sorted the problem out a while ago now, pulled all the brake lines out, master cylinder apart and gave it a good clean with white spirits and air comp, new fluid and a bleed and all was good! the amount of crap i got out was amazing, 30 odd years of build up i guess!