Thanks so much for the advice! It turns out that it's possible to get the expansion valve out from the engine bay without touching the dash, so flushing the evaporator in-place should hopefully be an option. It's good to know that leak-testing with a sniffer is OK - I hadn't quite realized how sensi...

I'm the proud (?) owner of a 1989 Peugeot 405 Mi16, and need some advice on a bit of a saga that I've been going through with its air conditioning. Long story short, I'm looking for advice on how much oil to add to compensate for a fairly large persistent leak. There's a fair bit of backstory though...