I took the front end off my 2001 BMW E46 M3 to replace some squeaky pulleys and troubleshoot the AC, which has a leak. The AC condenser was filled with crud, when I cleaned it off I found it is badly rotted out, and needs to be replaced. Along with replacing that I plan to rebuild or replace the compressor as I saw some signs it had leaked as well under a UV inspection. The AC belt will also be replaced.

AC is not one of my areas of expertise, I'm not sure what else to replace, check or otherwise maintain while I have it all apart. I'm thinking it's a good idea replace the AC dryer as it's cheap to do and I don't know how long the current one has been on. The hoses all look fine, no signs of cracking but should I replace them too? Am I missing anything?

1 Answer 1


There are two things I can think of to do besides replace the drier (as you suggested you were going to do).

Along with what you stated, I'd replace the O-rings throughout the system. You'll have most of it apart anyways, and it would be good maintenance to replace these while you're at it. O-rings are very cheap insurance. Make sure you lubricate them with the proper PAG oil prior to placing them so they'll seal as well as slide on the metal parts without receiving damage.

Also, make sure you clean all of the lines. There are kits you can buy which will assist you in this. If the condenser is actually filled with crud (I'm think you're actually talking about the outside, though), it only makes sense the rest of the system may have become contaminated at the same time.

  • That's a good point about cleaning the system, the condenser is in bad enough shape it could be contaminating the system. This is becoming a bigger and bigger job the more I dig into it. Now I'm thinking I'll have to replace the radiator as well, I've found the alternator's squeaky, and I can't find a replacement for the water pump that won't break after 40k miles. Still, it's better to find these things out now.
    – GdD
    Jan 22 at 21:08
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    Like stated above, replacing the dryer is standard procedure when repairing a system that has been opened. I would go ahead and replace the expansion valve also, just because the system was contaminated and they are usually very inexpensive.
    – Jupiter
    Jan 23 at 0:22

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