I'll swear to Gawd, a lot of folks, either prior owners, or present owners must create a lot of these problems for themselves.
Right or wrong
Just my 2p worth.
Can't comment on Mk3 as I'm not that rich
With Roy (Hondo)
Two things kill Renaults (& other cars)
Sogginess & Lack of Maintenance.
Sogginess is caused by lack of maintenance. Sun roof drains & Scuttle Drains, for instance.
Bad maintenance:- leaving covers off fuse boxes, not replacing inner wing liners properly.
Owner NOT having belts changed timely.
Not being serviced / missing
Diesel owners only using them round town, so the
& DPF never get hot enough to remove the soot.
IMHO A well serviced high mileage car, is inherently more reliable than a garage queen.
You haven't said which S3 you intend buying. The 1.5 dcI engine seems to give most trouble from what I read on here. BUT compare fault report quantity against numbers sold. Should give a fairer idea of reliability.