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E24 (1976 - 1989)
The BMW 6 Series (E24) was the first variant of the 6 series produced by BMW from 1976 through 1989.

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  #1  
Old 10-15-2012, 05:13 AM
Harflint Harflint is offline
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Mein Auto: 1985 635csi
Power assist pump noise

I have a pretty loud scraping/grinding noise coming from the power assist pump. The accumulator and the pump have been changed. I have a good mechanic. His theory is that it's air in the pump. It started when I returned from a month away and started the car up - never heard it until then. It may leak but only a very small amount. We can't figure out what's going on. Any help?
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  #2  
Old 10-15-2012, 08:55 AM
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hornhospital hornhospital is offline
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Are you certain it's the pump? If the pump's been changed and the noise persisted, it's not the pump (unless your replacement was used and had the same problem? ) Look to adjacent stuff that's actually making the noise. You could always loosen the belt to the pump and remove it (yes, I know it's a pain to get to), then start it briefly to determine if it's indeed the PS pump or something else.

I agree with your mechanic. It's something beside the PS pump.
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  #3  
Old 10-15-2012, 09:17 AM
Harflint Harflint is offline
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Thanks - Yes, unless the replacement rebuilt pump had the same problem - unlikely. It's probably not the pump. I didn't know what else could make so much noise! Louder when I turn the wheel. Do you have any idea of what else it could be?
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  #4  
Old 10-15-2012, 09:33 AM
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hornhospital hornhospital is offline
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Being that it get's louder when you turn the wheel, nope. I'd have guess pump, too.

I just replaced a water pump in an '84 633 that was making all sorts of noise. You don't supposed it could be that, do you? It wouldn't explain how it gets louder with a wheel turn, though.

BTW, the water pump replacement turned into an adventure. Thread with pictures coming up.
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Quotes to live by:
guessing gets expensive...drivinfaster
nothing is more expensive than a cheap BMW...c4harpe13
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito) 7pilot

Ken Kanne, Silverhill, AL, E36 Forum Mod/Craigslist addict/Hoarder of all sorts of stuff
BMW-CCA #441426
1995 318is "Bebe"; 1993 325is "Elvira" 1985 635CSi "Katja" 1984 633CSi "Sylvia"
HAVE I HAD MY MEDS YET?

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  #5  
Old 10-15-2012, 10:39 AM
Harflint Harflint is offline
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The pump was just replaced with a rebuilt pump. That's why no one can figure it out. Is there anything else that could make that noise? It seems to have a small leak also, a few drips a day.
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  #6  
Old 10-15-2012, 11:30 AM
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hornhospital hornhospital is offline
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Mein Auto: 1995 318is / 1993 325is
If it's a newly rebuilt pump and leaks, I'd question the reliability of the rebuild. There should be zero leaks on a fresh pump, either new OEM or rebuilt. I wouldn't doubt it has internal problems, too, and could well be causing the noise. A mechanic's stethoscope would confirm it's the pump making the noise or some other part.

Did you get a warranty on the rebuilt pump?
__________________
Quotes to live by:
guessing gets expensive...drivinfaster
nothing is more expensive than a cheap BMW...c4harpe13
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito) 7pilot

Ken Kanne, Silverhill, AL, E36 Forum Mod/Craigslist addict/Hoarder of all sorts of stuff
BMW-CCA #441426
1995 318is "Bebe"; 1993 325is "Elvira" 1985 635CSi "Katja" 1984 633CSi "Sylvia"
HAVE I HAD MY MEDS YET?

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  #7  
Old 10-15-2012, 11:36 AM
Harflint Harflint is offline
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I don't think it's the pump that's leaking. The leak seems to be farther back, near the firewall, or somewhat forward of it. I'm pretty sure the pump isn't the issue. We need another solution. So far, it's a mystery. The leak could be related to air getting in, which is causing the pump to make noise, but the leak seems too small. So air must be getting in somewhere. When I pump the brake to check the fluid level in the reservoir there is a sort of foam in the fluid, or in the fluid that comes up when I pump.
Another visit to the mechanic I think.
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  #8  
Old 10-16-2012, 10:32 PM
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PETER NEWMAN PETER NEWMAN is offline
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Did you replace the sealing washers on the pipe banjo's, If not in my experience air is getting sucked into the system and it is air in the system making the noises, Peter
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  #9  
Old 10-17-2012, 06:54 AM
Harflint Harflint is offline
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Hi - What do you mean? My mechanic is doing the work and I am working with him to try tofigure it out. What do you mean "the sealing washers on the pipe banjos"? I agree that it sounds like air is getting into the system somehow - it seems like it's doing it while the car sits still - the noise usually goes away after a few miles of driving around town, then returns loud after it has sat parked for a few hours. I wish car talk was still on!
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  #10  
Old 10-17-2012, 08:18 AM
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PETER NEWMAN PETER NEWMAN is offline
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Smile

Hi there, A banjo is a threaded bolt which is hollow and it allows oil to flow through it and there are two on your pas pump. I found out many years ago on my 635 that after removing and refitting the pas pump whilst replacing the sump gasket I didn't replace the sealing washers and one of them allowed air to be sucked into the system and it made a terrible noise afterwards so I replaced the sealing washers and the noises ceased, Peter
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  #11  
Old 10-18-2012, 11:19 PM
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BMWFatherFigure BMWFatherFigure is offline
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The noise is either cavitation or the pump vanes lifting. Once you have fixed leaks jack up the front of the car and turn the wheel slowly lock to lock a few times to bleed out any air. Top up and then see how you go. Just how good was the rebuild on the pump? Is the pressure relief valve working correctly? Just thoughts.
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