I've got the same problem. Where can I purchase the genuine Ford 'o' ring, I've tried ford but there claiming they don't stock it. They can only sell me a new heater matrix.
I've bought an assorted box of o rings from Halfords, lubed up a 17x2.5 O ring and inserted it into the female grove on the pipe but now I can't join the pipes back together. Either the o ring is the wrong thickness or I'm doing summit wrong. What size o ring do I need.
right, found the picture that I took just after I bought these (for any future reference, so I'm glad I took it now). Not exactly sure which number it is as there are three, I'm presuming its the 1342708, but heres the photo anyway. give me a shout if you'd like me to email you the picture.