"Airmatic Compressor "On" Time?
Thread Starter
Junior Member
Joined: Feb 2007
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From: Chilliwack, BC, Canada
2007 GL450, 2007 335i with a Cobb tune (435HP)
"Airmatic Compressor "On" Time?
How much time is the Airmatic compressor actually supposed to be operating? It's got louder recently and so I hear it a lot more...most of the time the vehicle is in motion, in fact (kicks in at 40km/h and back out when slowing below 20km/h). I'm wondering if it's normal for the compressor to be operating that much and I just notice it now that it's loud, or if it's not supposed to be working nearly so much and there's a leak in the system which it's trying to keep up with?
Also, the pump never operates when the vehicle is at a standstill, and all 4 corners of the vehicle look like they're supposed to look--haven't seen one drop yet or had any codes thrown. One thing I have to say about that though ... I measured the distance from the garage floor to the bodywork, with each wheel hub as my centre point, and none of the measurements were equal (33", 33.25", 33.5" and 34"). I'm guessing that's within a level of tolerance???
Anyway, any light shed on this would be appreciated. Thanks!
Also, the pump never operates when the vehicle is at a standstill, and all 4 corners of the vehicle look like they're supposed to look--haven't seen one drop yet or had any codes thrown. One thing I have to say about that though ... I measured the distance from the garage floor to the bodywork, with each wheel hub as my centre point, and none of the measurements were equal (33", 33.25", 33.5" and 34"). I'm guessing that's within a level of tolerance???
Anyway, any light shed on this would be appreciated. Thanks!
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compressor total running time can be queried with das/ star.
there is also a diagnostic routine that will pressurize the compressor integrated reservour - it should be able to reach 20 bars in short order (10-15 secs).
most (older) compressors will fail along the seam on the reservour. new compressors are updated to not have that seam.
there is also a diagnostic routine that will pressurize the compressor integrated reservour - it should be able to reach 20 bars in short order (10-15 secs).
most (older) compressors will fail along the seam on the reservour. new compressors are updated to not have that seam.
Last edited by alx; Nov 4, 2014 at 02:28 PM.
MBWorld Fanatic!
Joined: Dec 2006
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From: Clifton, NJ
96 and 08 911 turbos
compressor total running time can be queried with das/ star.
there is also a diagnostic routine that will pressurize the compressor integrated reservour - it should be able to reach 20 bars in short order (10-15 secs).
most (older) compressors will fail along the seam on the reservour. new compressors are updated to not have that seam.
there is also a diagnostic routine that will pressurize the compressor integrated reservour - it should be able to reach 20 bars in short order (10-15 secs).
most (older) compressors will fail along the seam on the reservour. new compressors are updated to not have that seam.
As to how much it should run, that depends on what kind of roads your driving on and how you're driving (hard accel/braking, cornering etc.)
It shouldn't be running for more than maybe 20 seconds at a shot though and not very frequently. If you find it running very frequently, you likely have a leak someplace.
Thread Starter
Junior Member
Joined: Feb 2007
Posts: 17
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From: Chilliwack, BC, Canada
2007 GL450, 2007 335i with a Cobb tune (435HP)
Great, thanks guys. Yeah, it's running solid for many many minutes, driving like a grandpa. I found a minuscule leak in one of the air lines. It's very tiny though...not sure if it's enough to warrant what's happening. I'll patch that properly and then take it from there.
How loud is the compressor supposed to be? Mine's currently loud enough that you can easily hear it when driving, with the radio not up too high.
Again, much thanks!
How loud is the compressor supposed to be? Mine's currently loud enough that you can easily hear it when driving, with the radio not up too high.
Again, much thanks!
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Joined: Dec 2004
Posts: 4,268
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20 bars is excessive from my experience. My DAS compressor test is 14 bar, and yes, it should reach that within about 15 seconds no problem.
As to how much it should run, that depends on what kind of roads your driving on and how you're driving (hard accel/braking, cornering etc.)
It shouldn't be running for more than maybe 20 seconds at a shot though and not very frequently. If you find it running very frequently, you likely have a leak someplace.
As to how much it should run, that depends on what kind of roads your driving on and how you're driving (hard accel/braking, cornering etc.)
It shouldn't be running for more than maybe 20 seconds at a shot though and not very frequently. If you find it running very frequently, you likely have a leak someplace.
Can't recall from memory but I think at 14 bars the das test will actually fail.
Thread Starter
Junior Member
Joined: Feb 2007
Posts: 17
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From: Chilliwack, BC, Canada
2007 GL450, 2007 335i with a Cobb tune (435HP)
So, found a leak in one of the air lines. The tech cut out the cracked bit and bridged it. Now it's working fine. After a start-up it kicks in at 40 km/h, as it should, and only runs for 10 to just over 20 seconds, and then I don't hear it again for the rest of a trip. The compressor certainly is noisy though, but is keeping pressure with no problem. I think the tech said it tested at close to 20.
If the compressor fails I'm going to replace that myself and save some money. Easy job.
Again, thanks for the responses all. Have a great weekend. <insert beer mug emoticon here>
If the compressor fails I'm going to replace that myself and save some money. Easy job.
Again, thanks for the responses all. Have a great weekend. <insert beer mug emoticon here>
MBWorld Fanatic!
Joined: Dec 2006
Posts: 4,949
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From: Clifton, NJ
96 and 08 911 turbos
good to know. I ran the test on my w220 which only calls for 14bar.
