While I do not own an E30 M3, I have a 318i and BMW dealer says that the evaporator is leaking and costs about over $1000.00 to r/r it. Well, since I have full set of tools + AC tools, I decide to check the system mysefl to see if the dealer telling the true. They lie! it is not the evaporator, it's the expansion valve. I r/r it along with a new drier, now after $200.00, my ac is cold, very cold, even in the sheer heat of Texas afternoon