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Thread: 735i (very) Cold Start Video - Possible Vacuum Leak after 45 seconds?

  1. #1
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    Question 735i (very) Cold Start Video - Possible Vacuum Leak after 45 seconds?

    I always hear a whining sound after 45-60 seconds of starting the car when cold. Seems to start off almost perfectly, but then the whining starts and the idle seems to oscillate. Also note the weird behavior when giving it a little gas and then letting off the throttle quickly.

    All vacuum & air-intake hoses have been replaced. The ICV and AFM have been cleaned/tested, along with the TPS.

    Does this sound like a bad valve cover gasket? Intake manifold gaskets?? Any input is appreciated!

    https://drive.google.com/file/d/1G4R...ew?usp=sharing
    Last edited by CamE32; 01-12-2019 at 12:27 PM.
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  2. #2
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    Chatham, Ontario, Canada
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    1988 BMW 735i
    Mine makes the same sound as that, although I think of it being more like a whistle sound.
    I haven't figured out what causes it but on my car at least, it sounds like it's coming from the passenger side of the engine bay.


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  3. #3
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    Whistling is a much better description, thank you. And mine seems to be emanating from the passenger side also!
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  4. #4
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    I'm not sure but I'm wondering if it isn't air moving through the intake that's causing it, but I haven't looked at mine close enough to tell.


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  5. #5
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    1990 735I (E32) M30
    Imagine if a 1/2 second shot of belt spray on your three belts made it all go away. Sometimes our M30 motors require a bit of magic.

    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=JhiZkLGPtqw
    https://www.youtube.com/watch?v=e7bNEQoLw-4

  6. #6
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    Quote Originally Posted by CroughtonE32 View Post
    Imagine if a 1/2 second shot of belt spray on your three belts made it all go away. Sometimes our M30 motors require a bit of magic.
    Really??? Iíll try it if you think thatís actually symptomatic of the whistling noise. I only question it because I had them all replaced within a year ago.
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  7. #7
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    Quote Originally Posted by CamE32 View Post
    Really??? Iíll try it if you think thatís actually symptomatic of the whistling noise. I only question it because I had them all replaced within a year ago.
    Iím just throwing it out there. Might work. Could be coming from a pulley after warm up. Hell, if I didnít want the world jumping in, Iíd blame the whistle on our infamous ďmustard relayĒ. But I wonít. Only because itís Sunday.


    Sent from my iPhone using Tapatalk
    1990 735I (Auto) E32 Feb 1990 to Present
    1996 Z3 Roadster (5 Speed) E36/7 Jan 1999 to Dec 1999
    1983 733I (5 Speed) E23 April 1983 to Feb 1990
    https://www.youtube.com/watch?v=JhiZkLGPtqw
    https://www.youtube.com/watch?v=e7bNEQoLw-4

  8. #8
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    1989 BMW 735i
    That sounds very much like a belt/pulley issue to me. The belt dressing is where I would start, then perhaps check the bearings in your alternator.
    I haven't had it on our 735, but I have had a very similar sound on some of our other vehicles. On one it turned out to be the water pump.

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