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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

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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  #1  
Old 02-26-2012, 10:34 PM
idjit's Avatar
idjit idjit is offline
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Hissing sound - interior temp sensor

2003 525i

My mechanic replaced all vacuum lines around the engine. When done he heard hissing inside the cabin. He blocked off what he called "air discharge sensor" and blamed it on the increased flow after fixing all the leaks under the hood. He finished off with a successful smoke test. Curiosity had me look under the dash.

I dropped the small panel under the driver side and attached to it, and very close to the scan tool connector, I found a black sensor with a 2 wire connector and the plugged off hose sitting beside it. The hose, when attached, would suck air from the footwell area.

A bit of searching identified this as the interior temperature sensor used to regulate a constant temperature in the cabin. They suck air past it to get a more accurate (faster?) reading.

I saw nothing to indicate a fault in this very simple sensor so I unplugged the vacuum line and reconnected it. Now it hisses again and I can't help but think there must have been a restrictor somewhere in the line to reduce the flow. At the sensor itself there is a plastic adapter between it and the vacuum line but it's obviously not slowing the air flow enough. Also, he wasn't frigging under there until after he fixed all the hoses under the hood. I think, somewhere, he frigged something closer to the engine end of the vacuum line.

Question, is it possible he's discarded a restrictor from under the hood somewhere or swapped a couple of connections somewhere?

This might be a good time to mention my new codes in the AM. P0491, p0492 that also came with the return of the car to me after the work and after I hooked this hose back up. I know what they are (secondary air flow) and I can hear the pump running and I know a small vacuum leak can throw the codes, so, again, I wonder about a missing restrictor or swapped vaccum lines.

I've plugged the hose off again to see if the codes disappear and will post the results in a couple days of cold starts but, meanwhile, could someone please comment on the high airflow on this sensor?


Thanks -Bob
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  #2  
Old 02-27-2012, 03:44 AM
JimLev JimLev is offline
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The cabin air temp sensor is in the HVAC panel in the center of the dash below the MID, not sure what you are referring to. I don't have any vacuum lines in that location.
Look at the vac lines to the secondary air valve, either one could be defective.
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  #3  
Old 02-27-2012, 04:08 AM
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idjit idjit is offline
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Hi Jimlev!

I've attached a picture. As you can see I have it blocked off today. The air sucks right through this unrestricted except for that black plasic adapter between the hose and the plug which isn't very restrictive. The air comes up from below as this unit is mounted in a hole in the cover that it as attached to. There is a sensor in the air passage and a small air filter in the top portion.

Look at page 13 and 14 of this document:
http://www.bmwmotorsports.org/BMW_docs/2001changes.pdf
It's the word "footwell" to look for (mind you, mine is a 2003, not 2001).

Here's an old post that suggestes a restrictor may be missing:
http://www.mye28.com/viewtopic.php?t=54562
Down a bit they start discussing the unit I'm speaking of and they come short of explaining where the restrictor is located and a part number.

The line along the valve cover to the secondary air valve was replaced, but I didn't get any codes this AM at -13C with it capped off and was getting them every morning and I swear the car is peppier today.

Given that this is work done at the same time and by the same mechanic that reversed the purge valve and oil pressure switch cables which left me stranded, I expect it's another error.

This is a Canadian model. I wonder if somethings different up here (besides my mechanic).
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Last edited by idjit; 02-27-2012 at 06:13 AM.
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  #4  
Old 02-27-2012, 06:40 AM
JimLev JimLev is offline
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Thanks for the pic and the link. I was thinking you had the IHKA temp system.
The IHKA doesn't use that sensor.
Now that you mentioned this was the same mechanic that had swapped connectors and told you the DME was bad, you may be correct, he hooked the vac lines up wrong.
Both those P codes are for insufficent secondary air flow.
You could try to unplug that line and see if the P codes return, it could take a few cold starts for them to come back.
Do you know where the other end of that vac line is suppose to connect to?
What's the last 7 of your VIN, that may be the quickest way to find that vac line.
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  #5  
Old 02-27-2012, 07:22 AM
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idjit idjit is offline
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VIN = GY98606

My problem is that I have no place to work. I'm trying to load up knowledge for the weekend and hope for warm weather. This time of year here it's quite possible to be warm during the day. I do not want to take this car back to him cause then it will be something else and he'll make me pay. He likes to call these issues "coincidence".

I'm assuming where ever this goes to is either restricted or a restrictor was in the vac line near the engine. He wasn't under the dash until he heard the hissing.

I tried an email to the old post on the other forum (above), but have not had a reply. That posting was in 2008.

Last edited by idjit; 02-27-2012 at 12:07 PM.
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  #6  
Old 02-27-2012, 07:55 AM
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idjit idjit is offline
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I should mention, when the line was plugged, before when the wire connectors were reversed, these codes were not there. After I uncapped and reconnected the hose they showed up. Last night I capped the hose off and the codes left. I'm sure it's affecting it and will keep an eye on it. My code reader is always within reach now
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  #7  
Old 02-27-2012, 02:39 PM
JimLev JimLev is offline
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Not having an I6 with the IHRA temp control the only thing I could come up with is that you have one of these sensors on both sides, B26 & B27.
There is an electrical connector for sensing the temp in the footwell area. The connectors are X900 & X901.
Does the sensor on the other side make the hissing sound too?
Still don't know where the vacuum lines connect to.
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  #8  
Old 02-27-2012, 03:08 PM
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idjit idjit is offline
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It looks like it might be buried in snow by morning so I ran out with a flashlight. The passenger side panel is made to take one but there isn't one there. I dosn't look like there ever was.

I tried to follow the hose from the driver side over lunch hour. It goes to the center and I can feel it on what I think is a plastic junction. Whatever it is its not attached to anything. I also noticed under the hood a line comes through the firewall (or attaches) from between two big rad hoses (either heater core or tranny I suppose) and straight to the intake manifold. There's a pic on my blackberry which I left at work. From diagrams I think the hose from the secondary air valve works itself around to an electric valve and on to here also as well as the non-return valve. If so, I wonder if one of these attach points has, by design, restricted airflow. I think more likely something was in line on the actual hose. My goldwing has a restrictor to a fume thingy in the false gas tank. Seems like a logical way to restrict the flow.

I think the only purpose of the vacuum hose on this sensor is to pull cabin air over the sensor within it. Without air restriction it is a major vacuum leak.

Still no codes while the hose is capped.

I hope the weekend is nice enough that I can tear into this far enough to see.

Last edited by idjit; 02-27-2012 at 03:48 PM.
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  #9  
Old 03-01-2012, 02:43 PM
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idjit idjit is offline
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Had a quick look (feel) tonight before it got dark. The hose from the non-return valve is connected to the intake manifold. Looking from the back of the engine, as if that's possible, to the left is a capped off connection. Below and perhaps halfway between these two is the hose that feeds into the cabin through the firewall. Does that sound correct?

Last edited by idjit; 03-01-2012 at 02:49 PM.
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  #10  
Old 05-16-2012, 09:55 AM
topgear454 topgear454 is offline
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I'm dealing with the exact same problem (minus the codes). The vac line goes to a manifold vacuum source. This is evidenced by the sucking noise stopping with increased throttle position as manifold vacuum is reduced.

Did you ever have a resolution. I'm expecting I will need a new sensor...
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  #11  
Old 05-16-2012, 01:39 PM
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idjit idjit is offline
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Yes,

In another thread: http://www.bimmerfest.com/forums/sho...ghlight=vacuum

You can skip right to the end (page 5) where I list the part number and mention the adapter that my mechanic had not thrown out, but it's a very interesting thread start to finish. It's worth skimming through it.

So, basically, theres a line from the intake manifold to the adapter and then the line with the restrictor in it that continues on to the firewall. Did you see the picture of where the sensor is in my car? Apparently it's unique.
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  #12  
Old 09-17-2012, 12:44 PM
trailblazer trailblazer is offline
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Red face

I'm dealing with the exact same issue and I think I'm pretty close to resolving it.

They introduced this sensor in 2001 and only for the IHKR (3 dials) A/C system.

Previous owner used GUM to clog the line from under the kick panel.

My 6" hose in the engine bay to the firewall was rotted to all hell. I've temporarily plugged the line going to the intake manifold with a screw until I get the proper restricted hose.

I believe the part number referenced in the previous thread is 64 11 1 384 459. Once I get the part and install it I'll report back with results.
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  #13  
Old 09-18-2012, 02:33 AM
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idjit idjit is offline
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From thread (I have a 2003 525i) "http://www.bimmerfest.com/forums/sho...ghlight=vacuum"

"I received P/N 64 11 1 386 446 air flow reducer yesterday for restricting the air flow to the interior temperature sensor. What you get is about 3 to 4 inches of braided vacuum line with something shoved inside to the center."

Other part numbers we unavailable, but this was and it fit and fixed the issue. It goes between the firewall and the little black connctor that should have been amongst your rotten tubing that you removed. Then a tube continues from the connector to the intake manifild.
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  #14  
Old 09-18-2012, 09:41 AM
trailblazer trailblazer is offline
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Hmmm, I wonder where I got my part# from. I'm going to continue to dig a little deeper before I order a part.

I found some very very helpful diagrams I figured I should share with this thread through.

http://parts.bmwofsouthatlanta.com/s...ssembly=423227

http://parts.bmwofsouthatlanta.com/s...ssembly=262615

In case that site goes down, here's a picture too.


After a little cross referencing with RealOEM I have discovered the part I posted (459) is for the following
E32 740iL Sedan, M60, AUTO (GD83) : ELECTRIC PARTS FOR HEATER
E53 X5 3.0i SUV, M54 (FA53) : Vacuum control, interior temperature
E53 X5 3.0i SUV, M54 (FA13) : Vacuum control, interior temperature

The 446 part number is for the following
E24, E28, E30

I'm going to take my chances with the 459 and report back with the results. They're probably identical.

Last edited by trailblazer; 09-18-2012 at 10:00 AM. Reason: MOAR INFO
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