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Thread: a/c compressor with death rattle

  1. #1
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    a/c compressor with death rattle

    Hi All

    The other day I pulled up at home to get the mail and noticed a metallic rattle coming from my car After finding out the noise was coming from my A/C compressor. I drove the car into the garage to have a better look into the noise I found out the noise was only there when the A/C was on it was worse after the A/C clutch was ingauged (so I parked the car and took my wife car to work for the next few days)

    I made some inquires with a A/C expert to get the confrmation the comperssor need replacing. I asked him for a general price He jokeingly said about $1000 for the compressor alone

    Anyway I looked into some prices on the net and found a brand new compressor for about AU$450 on US Ebay
    http://cgi.ebay.com/ebaymotors/ws/eB...3AIT&viewitem=

    Has anybody bought one of these unit before ???

  2. #2
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    Go through Jared at EAC tuning. He has compressors for $570. they're brand new OEM compressors.

    One problem though. I dont know if he's got parts for the 523i. Worth a shot though.

  3. #3
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    Quote Originally Posted by Aussie523i View Post
    Hi All

    The other day I pulled up at home to get the mail and noticed a metallic rattle coming from my car After finding out the noise was coming from my A/C compressor. I drove the car into the garage to have a better look into the noise I found out the noise was only there when the A/C was on it was worse after the A/C clutch was ingauged (so I parked the car and took my wife car to work for the next few days)

    I made some inquires with a A/C expert to get the confrmation the comperssor need replacing. I asked him for a general price He jokeingly said about $1000 for the compressor alone

    Anyway I looked into some prices on the net and found a brand new compressor for about AU$450 on US Ebay
    http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=130276346818&sspagenam e=STRK%3AMEWAX%3AIT&viewitem=

    Has anybody bought one of these unit before ???
    I'm in the process of getting mine fixed too. I've been rattling for six months or so now...

    Above poster hit it on the head, $570, with a 60 dollar core charge. It's about as cheap as you're going to find it. I had my local indy shop quote me $1100 for the compressor.
    I can haz Zionsville?



  4. #4
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    Are you 100% certain it's the compressor and not the pulley/deflector just above/next to it? A $75.00 pulley sounds better. If it's the compressor, you're in Australia and need ac!
    "I'd smash that (Jennifer Connelly) like a failed coup in sub-Saharan Africa."
    ~Macktheknife in my epic Jennifer Connelly OT Thread

  5. #5
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    a/c compressor with death rattle

    Quote Originally Posted by bimmerfiver View Post
    Are you 100% certain it's the compressor and not the pulley/deflector just above/next to it? A $75.00 pulley sounds better. If it's the compressor, you're in Australia and need ac!
    Yes I have checked the Clutch bearing the idler bearing. The noise only there when the A/C is on. It goes away when the A/C is Off

    George

  6. #6
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    George,

    Sorry to rehash an old post. Did you ever get to the bottom of what was causing your rattle? I've got a similar sound coming from the Denso compressor on my 95 525i. Only rattles when the compressor clutch is engaged and the a/c compressor is on.

    Thanks!

    SS
    Scottie Sharpe
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  7. #7
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    Hi

    The compressor was on it way out. I have replaced it with a brand new compressor and drier and had the system regassed. Still working fine to this day
    96 523I


  8. #8
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    Quote Originally Posted by scottie View Post
    George,

    Sorry to rehash an old post. Did you ever get to the bottom of what was causing your rattle? I've got a similar sound coming from the Denso compressor on my 95 525i. Only rattles when the compressor clutch is engaged and the a/c compressor is on.

    Thanks!

    SS
    My 95 has been doing it for YEARS. Still runs though. I'll fix it when it quits.

  9. #9
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    Thanks Guys! Tomorrow I will inspect the belts, tensioners and clutch mechanism and see if anything is awry.

    I have a spare Denso compressor here that I pulled off a parts car some years ago, so I may swap that in if I can't find any obvious problems.
    Scottie Sharpe
    68 2002 M20 Conversion, G265, Ireland coilovers, e12 brakes
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  10. #10
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    Also check the pressures, some compressors can start knocking when the refrigerant gets low and they are struggling to suck in enough refrigerant.

    The A/C clutches do sometimes go out and make noises, and those can be replaced by themselves.

    I would fix a rattling compressor sooner, rather than later! I lived with a rattling compressor in my Impala for a while, and it shredded itself inside and sent metal shavings everywhere. I wound up having to replace everything except the evaporator core, it was not fun or cheap!

  11. #11
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    Thumbs up

    Pressure seems ok. It was hot here yesterday when I was testing. Around 90' F ambient. At start up (cold) a/c compressor was quiet. Intake pressure was 40 lbs. Discharge pressure was 190 lbs. Vent temp was 43'.

    Noise only occurs when A/C clutch engages, so I am inclined to think that it is not the clutch bearing. The bearing only spins when the clutch is not engaged (freewheeling).

    Once things warmed up, the compressor makes a metallic rattling noise, but only when the clutch engages.

    Manifold pressure once warmed up: low 45 lbs, high 205.

    One interesting thing I noticed: Even with the windows open and ambient temps high, both temp controls at their coldest setting (driver's side in the "cold" detent position), fan on high. The compressor would cycle on and off ever 2-3 seconds or so. This seems like a very small cycle increment to me.

    I've never owned a BMW that would cycle that quickly. However this is my first BMW with a Denso compressor.

    If I can't figure out what is causing the noise, I will replace the compressor with the one I have here. I am fearful of it destroying itself and blowing metal shavings all throughout the system.

    I have all the tools I need, except I don't own a recovery unit. Kind of a pain to take it in and have the freon recovered.

    Anyone know a shop in Silicon Valley that will recover R134 cheap or free?

    By the way, I found this video on YT. Not my video. This is the exact sound I have. The three knocks is the guy signaling the person in the car to switch the AC. But listen to the rattle. That's what I have.

    youtu.be/idc94pWb5f4

    Thanks for your help guys!
    Last edited by scottie; 08-11-2012 at 03:23 PM.
    Scottie Sharpe
    68 2002 M20 Conversion, G265, Ireland coilovers, e12 brakes
    88 Dinan M5, M88/3 Conversion, Dinan Stage 4, Miller MAF and WAR, Perfect Power SMT6, B&B exhaust, Racelogic Traction Control and Launch
    95 525i
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    62 R60/2
    Webmaster for M102/M106 discussion group http://bmwturbos.scottiesharpe.com

  12. #12
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    Quote Originally Posted by scottie View Post

    ... stuff deleted ...
    One interesting thing I noticed: Even with the windows open and ambient temps high, both temp controls at their coldest setting (driver's side in the "cold" detent position), fan on high. The compressor would cycle on and off ever 2-3 seconds or so. This seems like a very small cycle increment to me.

    I've never owned a BMW that would cycle that quickly. However this is my first BMW with a Denso compressor.
    ... stuff deleted ...
    I'd understood that all year's E39 A/C compressors were variable displacement designs and therefore did not regulate by switching the compressor clutch on and off. Can anyone confirm this one way or the other?

    If so, the compressor cycling indicates a malfunction.

    Regards
    RDL

  13. #13
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    I'm sorry! I've created a Zombie from an old thread and discussing an e34 in an e39 forum.

    My car is a e34 '95 525i. Sorry for the confusion.
    Scottie Sharpe
    68 2002 M20 Conversion, G265, Ireland coilovers, e12 brakes
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  14. #14
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    Quote Originally Posted by scottie View Post
    I'm sorry! I've created a Zombie from an old thread and discussing an e34 in an e39 forum.

    My car is a e34 '95 525i. Sorry for the confusion.
    No harm done. Visiting is allowed, even when it's inadvertent.

    You are more likely to get useful suggestions in the E34 section though.

    Regards
    RDL

  15. #15
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    This is only a guess, but I think you're probably low on refrigerant. If it's cycling like that and your high side pressure isn't climbing way up, it typically needs more refrigerant. Since the refrigerant carries the oil, it's possible that the low refrig. has caused an oil starvation issue. If it were me and I was counting on having to likely replace the compressor anyway, I'd add a can of 134a with compressor oil in it. Too much oil in the system isn't a good thing, but having a few ounces too much isn't a big concern in a car because of the accumulator (reciever/drier). I'd do that and see if it quiets down. If it doesn't, change the compressor before it sends internal trash to the other parts.
    Last edited by 514mach1; 08-12-2012 at 12:23 AM.

  16. #16
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    I wanted to find out the cause of the rattle in the compressor so I put in on the bench and took it apart. One I had the clutch off, I noticed that the compressor shaft has about 0.3mm of end play. When I move the shaft in and out, it makes a click/tap sound which I think could most certainly sound like a "rattle" at higher speed, as the belt wiggles and moves the pulley in and out a tiny bit (.3 mm).

    I disassembled the compressor fully to check all of the bearings and wobble disk. All the bearings appeared great, no pitting. There was plenty of oil in there and there was no sign of any damage. The cylinder bores and pistons all looked clean and not scratched at all. One thing that I noted was the wobble shaft bearings that allow the pistons to ride the wobble shaft had play. A lot of play more than 1mm. However, they did not appear to be worn.

    This had me wondering if a good compressor would have this kind of wear, so I disassembled another Denso compressor I had to measure it. It had the same clearance in the wobble bearings. Also the wobble bearings had a teflon face whereas the wobble wearings in my compressor were all hardened metal. Interesting, but I think the spacing on my original compressor is correct. (I can't find any specs on this anywhere on the net. I found only one reference to rebuilding the Denso compressor on the Pelican site.)

    This lead me to believe that the end shaft play is causing the noise. I searched around the workshop for a shim material that I could use punch out into a shim for one of the bearings on the main shaft. However I didn't find anything. So what I did instead is I milled down the center case .1 mm on each side. This brought my end play down from 0.3 mm to 0.1 mm.

    I reassembled the unit with the existing seals as they looked perfectly fine and put the clutch back on. Now the shaft has no noticable end play and I can't make it "click/tap" anymore.

    I put 4 oz of Pag 46 in it and put it back on the car, snugged up the lines, and put a vacuum of 28" on it. Gonna let it sit overnight to see if holds.

    Tomorrow I'll put the belt and tensioner back on and fill it with propane to see if makes any funny sounds while it is operating.

    If all is well, I'll release the charge, draw another vacuum and fill with R134a.

    Will report back. Also I took pics of the compressor repair. Will post those.

    I have my fingers crossed....although I have to admit I keep browsing back to the ebay auction selling brand new Denso-style compressors for $180 and wondering ... is this even worth it?

    Ha ha!

    It'll probably blow up tomorrow and send shrapnel all through my system. We'll see!

    Some pics of the compressor rebuild.

    Latest test results at the end of this post.



    The trouble maker before I cleaned it and took it apart.







    Clearance between wobble plate and cam bearings. Seems excessive but I do not know what it is supposed to be. Took a "good' compressor apart and it also had the same clearance, but it had teflon faced bearings. Maybe the teflon stops the rattle? I just don't know.



    Cam bearings with teflon



    A mix of bearings from both compressors, showing some with teflon others without. I don't know why this is. I used the teflon bearings. Perhaps this is why I no longer have the rattle. Will we ever know?!?!



    Getting the thing reassembled requires five hands. I don't know how I did it.



    It's like one of those bar games where you have put the pieces together when you're drunk...but about 10 times harder.

    Reassembled last night and the system held a 28" vacuum all night.

    System already had 4 oz of PAG46 in it.

    Today I filled the system with 1 lb of propane and ran some pressure calc. Suction 80 psi, 265 psi, ambient 92F in the shade, 40F vent temp. No funny noises or leaks. Compressor has stopped making the rattle sound.



    With R22a (propane) blowing cold temps.


    But I will not run the car with propane. Just for testing so I don't waste any freon in case things aren't well with the system. Obviously it is not safe to run propane in a car system.

    So now that I have confirmed that it is working, I will vacuum it and recharge with 1550 grams of R134a as per the label and run it for a bit.

    So here is my analysis of the famous "death rattle":

    Is it a case of the wobble bearings wearing out? I don't think so and this is only because the wobble bearings do not look worn on either of my compressors. However one could clearly assume that the "rattle" could be the sound of all 10 wobble shaft bearings flopping around inside their bores. That would definitely make one heck of a rattle.

    Is it a case of the teflon faced bearings vs the all steel bearings? I think not since many compressors out there probably have some or the other and there does not seem to be a recall on all-steel bearing compressors or anything.

    Lastly, is it a simple case of excessive end play on the compressor shaft? Yes, I think so. And if that is truly the case, then I think it is NOT the cause of compressor failure, as everyone says. Based on what I've learned about taking one of these Denso's apart, a little end play noise is simply NOT going to cause a compressor to fail. Anyone who has had a failure on a "rattling" compressor, either one day or one decade after noticing the rattle --- I just do not think the two are related.

    If I had a rattling compressor, I'd remove the clutch assembly from the car and check the end play. This can be done with the compressor lines still connected, but it would be difficult to do. If I had excessive end play, I'd shim the clutch to remove the excessive play. (the shims are available from BMW).

    Was it worth taking the whole thing apart and diagnosing that? No. I should have just bought a new compressor for 180 on ebay. However I have never taken a Denso compressor apart before, so now I know how they work.


    I also know that I can rebuild my spare denso compressor for my e28 M5 for the time when I "upgrade" the AC on that car to R134a. My plan there is to install the Denso compressor and the larger condensor from the e23 and install a more modern front electric fan(s).

    I just put a can of R12 in the M5 system and it working great, however the hoses are beginning to seep just a little bit (bubbles in the rubber near the crimps), so maybe I'll rebuild it in the next two years or so.

    I'll report back on the wife's ac in a few months and let you know how it goes longer term. We still have many more months of hot weather here in San Jose!

    Links:

    Rebuilding a Denso Compressor

    Seals for Denso Compressors
    Last edited by scottie; 08-13-2012 at 06:27 PM. Reason: Automerged Doublepost
    Scottie Sharpe
    68 2002 M20 Conversion, G265, Ireland coilovers, e12 brakes
    88 Dinan M5, M88/3 Conversion, Dinan Stage 4, Miller MAF and WAR, Perfect Power SMT6, B&B exhaust, Racelogic Traction Control and Launch
    95 525i
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  17. #17
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    Update: Compressor started rattling again. Will buy a new compressor! Ha ha.

    I will take the old one apart to see if I can figure out what is failing.

    SS
    Scottie Sharpe
    68 2002 M20 Conversion, G265, Ireland coilovers, e12 brakes
    88 Dinan M5, M88/3 Conversion, Dinan Stage 4, Miller MAF and WAR, Perfect Power SMT6, B&B exhaust, Racelogic Traction Control and Launch
    95 525i
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    62 R60/2
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  18. #18
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    My compressor has been rattling, when system on, for 4 years. AC works perfect. Just another 540i noise not hurting performance. Vanos is noisy, ac compressor is noisy, troublesome lifter is noisy; going on 5 years with these annoyances! Car refuses to die, or under-perform! I am staying the course, until something gives it up!! ( '99 540iA w/ 159k btw)..loving this car, but will not whine if/when something fails.

  19. #19
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    Old thread but need to ask the AC gurus...

    My 1998 528i 5sp with 160K miles now develops a rattle ONLY when AC is on.
    When AC is off, the rattle goes away.
    Belt & Deflection pulley brand new.

    Questions:

    1. Is 160K miles around the time when the factory AC dies?

    2. I will stop using the AC for now (don't want "Black Death" with shrapnels everywhere in the system!), and get a brand-new Denso.
    Is everyone here happy with Denso?

    Thanks!

  20. #20
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    I has the death rattle on my 1998 528i a couple of years ago. It was the 7SB16C model. I replaced it with a used 7SBU16C model that solves that reed problem. It's been fine until recently when I stupidly sheared the pressure release valve (don't ask). I bought a new 7SBU16C.

    I find this model to be essentially bullet proof for my needs (hot muggy summer but short in duration).
    gmak: The Good, the Bad, and the Ugly. A journey with my new-to-me 2000 540i

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  21. #21
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    Quote Originally Posted by gmak View Post
    I has the death rattle on my 1998 528i a couple of years ago. It was the 7SB16C model. I replaced it with a used 7SBU16C model that solves that reed problem. It's been fine until recently when I stupidly sheared the pressure release valve (don't ask). I bought a new 7SBU16C.

    I find this model to be essentially bullet proof for my needs (hot muggy summer but short in duration).
    I just bought the Denso 471-1119 AC Compressor from Amazon dot com.
    I think this is the correct compressor.
    Do you know if 471-1119 is 7SB16C or 7SBU16C.

    PS: The pulley bearing has been free-wheeling for a while. I was planning on replacing the bearing but it is coincidence now that the compressor is complaining itself. It is better if I replace the whole thing.

    When did your compressor fail?

  22. #22
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    I never used the AC much in the past. I started using it more about 5 years ago. About 3 years ago, I started getting the predator noise. Once I researched and realized what it implied, I replaced it with a used one (about 2 years ago). Now, I've put in a new one.


    471-1119 is the part number on the box my 7SBU16C came in. I can't find a Denso part number on my old 7SBU16C. So if we can assume that the compressor was sent to me in its rightful box, then you have the 7SBU16C with the fixed reed problem.
    Last edited by gmak; 07-24-2016 at 12:42 PM.
    gmak: The Good, the Bad, and the Ugly. A journey with my new-to-me 2000 540i

    "Working on a BMW E39 is the best way to run out of time."

  23. #23
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    This AC has been interesting. A few weeks ago I had some noises:
    - Screeching noise in the morning...Turned out it was the Aux Fan motor, used the DIY by "PENER", replaced the Siemens motor, that noise is gone.
    - The 2nd noise is ONLY when AC is engaged (king of minor minor loose marble noise, which I am afraid if left unattended to ---> Black Death), I am 100% sure the noise is from the AC Compressor. Once I replace the compressor, I will report back.

    PS: Re vacuum prior to adding R134a, has anyone here rented an electric vacuum pump from places like Autozone, Advance Auto etc.?

    - - - Updated - - -

    Question re Vacuum Pump. I know I have 2 options before adding R134a:

    1. Go to the local shop, so they can vacuum the system for > 30 min., then they charge it for me.

    2. Vacuum the system myself: for this, what pump brand name (? Harbor Freight) etc. would be appreciated!

  24. #24
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    If you have R134a - you need to get a pro to vacuum it because of the disposal issue, no? I went to an Indy to get it done and it wasn't that expensive because they are reclaiming the R34a and selling it. I didn't use them to charge the system. I bought my own vacuum pump to test the system, and a manifold gauge. I switched to an R134a substitute so that I could charge and dis-charge myself in the future without the green guilt. As well, This stuff (Noracool, I think) doesn't react with moisture in the same way as R134a - so the o-rings last longer. There is also a tacky lube for the o-rings that I used so that they don't tear upon installation - it's also non-reactive with any refrigerant you use.

    It's good to put a vacuum on the system every 3 - 4 years, I believe, just to test the system.
    gmak: The Good, the Bad, and the Ugly. A journey with my new-to-me 2000 540i

    "Working on a BMW E39 is the best way to run out of time."

  25. #25
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    Bump:

    For those of you that had the death rattle, did your AC blow hot air as a result? I noticed the metallic sound this morning coming thru the vents when I started up the car. Everything worked fine so I tried to ignore it. When I went out for lunch, the car was only blowing hot air. I just recently (2 weeks ago) had the AC recharged and there were no leaks in the system. Maybe there is a leak now? Does this noise ever come about from low refrigerant in the system? Does this noise have any actually bearing on the functionality of the AC system?

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