Re: Air Conditioning (archive)

My wife has a new (BMW certified preowned) '98 E38 which we have now had about three months. Since summer started, we have noticed an irritating mechancial noise in the air conditioner as well as some gurgling and sucking noises. I think they are two separate problems. First, on the gurgling and sucking, I understand that there may be a TSB issued already on this, and a modification kit exists which alters the drain system to solve this problem (is this true?). Secondly the mechanical noise problem involves a light, but annoying pinging sound, which is intermittent and seems related to the periods that the compressor clutch is activated. It is discernable only through the ac outlet vents, leading me to conclude that it is an expansion coil operating issue. My conclusion is 1) That we have a defective coil, either with a solder defect in the junction of fins and tubes, allowing expansion slippage when larger amounts of refrigerant are introduced causing rapid rises in coil versus fin temperature, or 2) That there may be a piece of debris (a chuck of solder or carryover of dessicant) in the coil which is randomly banging against the tube surfaces when larger amounts of refrigerant pass through the expansion valve as the compressor cycles, but never has enough velocity to escape the coil and enter/ruin the compressor. At any rate, I'm going to make a warranty claim on both problems, and wonder whether some of you experienced tech guys can give me an opinion on whether my diagnosis is reasonably on the mark, or whether you know of similar problems on other E38s. Also, do you have experience with how BMWNA really stands behind their preowns from an warranty aspect. I've never encountered this kind of problem before on our many BMW's over the years. Otherwise, this car has been an awesome performer, although the V-8 sounds a little lusty after having driven the 7 series sixes since they began. (My wife even went out and bought a license plate for her new beauty, which says "7TH-ONE"). I will appreciate the benefit of your all's experience on this one. Bob H.

My '97 iL exhibits the same faint "tinking" sounds when the AC is on and I think your hypothesis #2 is a likely cause.

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