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Thread: A/C compressor questions

  1. #1
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    A/C compressor questions

    98 328is. A/C compressor has been getting noisier for a while now, 200K on the car. Belt and idler are not old, I've seen the damage from one failing and it's easier to do it too early than late. Anyway, it's getting pretty noisy, only with the A/C engaged so I don't think it's the clutch, it should be locked in. But I noticed the past couple of weeks A/C performance hasn't been what it used to be. Still ok, but not what it was nor what it should be and a quick glance doesn't show the telltale oil of a leak. So... basic questions are,

    do compressors fail gradually? That hasn't been my past experience, but everything isn't always the same.
    Brands of compressors. Appears to be two, along with many knockoffs. Just match the picture?
    Many replacement compressors seem to come with the top missing, manifold? Just swap the old one?
    Any brand to run like crazy from? I haven't heard great stories about rebuilds and knockoff new are cheaper anyway.

    I know the basics, I've worked on many systems and built a couple from scratch, any special quirks? New oil in the new compressor?
    98 328is
    02 525ita
    80 528i
    81 528ia
    and decades of owning and driving BMWs

  2. #2
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    There is a bearing in the clutch that gets noisy, it's replaceable, search for DIY's. If I were you I would start there and add a 2 ounce charge of PAG46 oil, and then charge the system if needed. Optionally you can replace the receiver dryer, but that would require a vacuum pump.
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
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  3. #3
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    I had to do some research on a new AC compressor as well, Denso is the brand and it comes with the required oil for an empty system. Not having enough R134 in the system can cause lack of AC performance, try doing a recharge.
    1995 Cosmoschwartz M3/2/5- Daily Driver
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  4. #4
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    I would buy a rebuilt compressor. About $150. Servicing the clutch seems like a pain. I tried to remove one but gave up because I did not have the special tools. You might be able to borrow them from autozone.

  5. #5
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    Quote Originally Posted by Eric93se View Post
    There is a bearing in the clutch that gets noisy, it's replaceable, search for DIY's. If I were you I would start there and add a 2 ounce charge of PAG46 oil, and then charge the system if needed. Optionally you can replace the receiver dryer, but that would require a vacuum pump.
    Unless this one is different than others I have worked on, and it may be, the clutch bearing is used when the A/C is off, not when it's engaged, it allows the pulley to freewheel without the compressor turning. I might throw a bit of oil in the system, but without the telltale dirty spot at the source of a leak I'm not optimistic. Oh well, I guess 200K isn't bad, just not great.
    98 328is
    02 525ita
    80 528i
    81 528ia
    and decades of owning and driving BMWs

  6. #6
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    Anyone swapped out an a/c compressor recently? Denso preferred replacement? Mine started making a horrible rattling noise when the clutch is engaged. System is still cooling well, but worried it’s going to seize up on me.

  7. #7
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    Quote Originally Posted by Twistytee View Post
    Anyone swapped out an a/c compressor recently? Denso preferred replacement? Mine started making a horrible rattling noise when the clutch is engaged. System is still cooling well, but worried it’s going to seize up on me.
    I have on my 97 328i....from autozone, which is great. What is not great, is I've now replaced it twice, and I keep getting a leak between the manifold (top) and the compressor itself. It would be nice if they came with the manifold too
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  8. #8
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    A couple of years later...

    It hasn't gotten better, cooling wise. But it's quiet again, however when pulling up to a stop sign it blows warm. I threw a can of 134a into it, might have slightly overcharged it and it's better. Eventually it stops the warm at a stop sign behavior, but it's pretty pronounced at first. Even at idle it appears to be cycling off the high side switch, it'll get down to about 41F, then rise 3 or 4 degrees at the vent before starting to come back down again. I really suspect it needs a compressor, but it's still working well enough I'm reluctant to spend the $$$ and do the work.

    I've worked on a number of A/C systems over the years and this one just doesn't make sense.
    98 328is
    02 525ita
    80 528i
    81 528ia
    and decades of owning and driving BMWs

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