Hi Nick.
A Last resort. have you seen this before. Great stuff, not cheap but may be worth a go.
I used it in a Transit 60,000 miles more, sold the van and she's still going now. not to sure how it would go in the exploreer but may be worth a try.
http://www.steelseal.co.uk/TESTIMONIALS-3-w.asp
Hope this is of help.
Clive