I remember some sealant that used to be out there (probably still is) they said it will stop evaporators from leaking . lol , We had a customer have us try it even after our warnings , (car was a 93 500 Sl 129 body ) anyways we put this stuff in and it clogged up the expansion valve , and had nothing but problems.
Needless to say we ended up replacing evaporator , expansion valve , reciever drier and flushing complete system due to contamination of this good for nothing @3*&$ . As you can tell the customer got a heavy bill and we got alot of headaches from flushing this car. The customer would have saved money just doing the evaporator and wouldnt have paid 2-3 xtra hours for disconnecting all lines and removing compressor for a flush. Evaporator on your car is right at 15hrs or so depending on your location. Have them replace all the vacuum servos while they are in there, you will thank me later. Good luck