Paula Xsara

I've just had our local Citroen dealer tell us that my 1.4LX (on a 51 plate) has a really badly corroded sump. So badly corroded in fact that they think it could 'burst' at any moment. Since it has sustained no accidental damage that I know of and is below average miles, this seems pretty unlikely. I'm also surprised that the item is, by implication, not steel and not alloy. Two questions: Can anyone comment on the potential for this type of corrosion (have you had this experience?)? And do you know of a reliable Citroen service centre that I could trust for a second opinion, I'm in the Bolton, Lancs. area). My first posting - treat me kindly