My dad recently brought a mk6 fiesta 1.4 tdci and after 2 months of using it the car needed new injector seals. So they was all replaced. However my dad has read reviews saying that its a common fault and that they can go every 20 thousand miles! Is that right?

 

I've done loads of these but I've not done many that fail more than once so i don't think its all that common. Usually its the injector leak off pipes that leak as the o ring fails. If you hear a chugging noise (like a train) its more than likely them.If they are done quickly and don't carbon up too much they should be ok when replaced.