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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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Old 05-09-2013, 02:15 PM
britton40 britton40 is offline
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Location: Maryland
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Mein Auto: 530i
Hissing noise from intake manifold

Every time I start my 2003 530i, I hear a hissing sound coming from the intake manifold. PS. Check Engine light on. Code P0491, P0492 and P0741. I need your help guys. Thanks
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Old 05-09-2013, 09:19 PM
Mjölnir Mjölnir is offline
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Mein Auto: E39 540i6, E36 M3/4/5
From what I can tell, the code P0741 related to the torque converter and thus unrelated to the hissing noise you hear from the manifold. The other two codes are for the secondary air system. I would guess that you have a vacuum leak which is causing the hissing noise. This may be responsible for the codes p0491 and P0492. You should try to determine specifically where the noise is originating, as that will likely lead you to the problem.
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Old 05-10-2013, 04:21 AM
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Fudman Fudman is offline
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Are you sure the sound is from the intake manifold? P0491 and p0492 indicates a secondary air pump (SAP) malfunction. That will throw a CEL. That hissing is probably your SAP pushing air out of a leaky hose or the SAP valve opening and allowing exhaust out of a leaky hose. This sound should only occur during a cold start, which is when the SAP activates. The cause of the problem could be a variety of things. You do not give sufficient info for a diagnosis. Search "SAP" and you will learn all about it.
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Old 05-11-2013, 12:26 PM
poolman poolman is offline
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Use the search engine at the top of the forum page---type in Vacuum leaks revisited I6 engines --that will give you the info you will need to find your leak at the back of your intake
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Old 05-11-2013, 02:48 PM
dvdlkd dvdlkd is offline
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The secondary air valve mounted to the exhaust on your engine has a vacuum line going to it. On some E39's this line runs aroung the front of the engine (97). On the 2000 it runs around the back. This vacuum line sees the radiant heat of the exhaust and is prone to cook/crack. trace this line the the valve under the intake manifold and replace if it is in bad shape. This could be your vacuum leak on starup because the valve feeding the vacuum line closes (stopping the vacuum leak) after ~2 minutes when the secondary air pump shuts down.
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