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Does your F355 make a hummin noise on start?

Discussion in 'Technical Q&A' started by F355Fly, Dec 31, 2003.

  1. F355Fly

    F355Fly Guest

    Nov 26, 2003
    54
    SoCal
    Full Name:
    Asi
    I have read a few posts here and have different things. My car (96 F355) makes kind of a high pitched noise on cold starts. Now I've read some posts that say it's the fuel pump and some that say it is the cam belt tensioneer/s. It only does it for a few minutes til its warm then goes away.
     
  2. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,337
    If it sounds like a (eminently present and anoying) screech and goes away in 15-20 seconds, its a tensioner bearing (or alternator idler bearing).

    If it sounds like a (barely audible) blower from the passenger side of the rear end, its the air pump used to ignite the catalyst.
     
  3. F355Fly

    F355Fly Guest

    Nov 26, 2003
    54
    SoCal
    Full Name:
    Asi
    I would say it goes on for more then 20 seconds and goes away only to be heard on the next cold start. Is there a way to tell for sure? I had the car over at the Ferrari Dealer last week for an oil change and clutch and brake fluid change and when I picked it up they didnt mention anything about it. Don't you think they would have brought it up?
     
  4. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
    Ft Laud
    Full Name:
    Frank Lipinski
    That is normal. What you are hearing is the air pump for the cats as previously mentioned - only on cold starts. To be sure, pop the hood and start her and you will see and hear the blower. It is in the extreme rear of the car on the right hand corner. There is a round pump appx 6 inches - creates a high pitch sound.

    Normally, I like to let her warm up and not drive her until the pump goes off. At that time you will also notice the water temp gauge just start to move.

    All is well.... not to worry.
     
  5. http://www.delobbo.com/trashman/F355Noise.mov

    Is this noise what you are describing? Can someone briefly explain why there is a need for an air pump for the cats? I'm planning on installing test pipes soon, the air pump will be irrelevant then right? Someone else mentioned it could be the exhaust bypass valve...not sure what that does either.
     
  6. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
    Ft Laud
    Full Name:
    Frank Lipinski
    A bypass valve sounds like a metal "clanging" noise and will go away a few minutes after you drive it.

    The pump makes a whine, almost like an electrical sound...
     
  7. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
    Ft Laud
    Full Name:
    Frank Lipinski
    The bypass valve does just that. In most gears at appx 4K RPM the valve allows the exhaust to bypass the cats and run straight out.

    Get an owners manual if you don't have one....most of this stuff is in there and explained very well. Also get a parts book...worth every penny...has a great detailed view of all the components and makes everything easier to understand...
    :)
     
  8. F355Fly

    F355Fly Guest

    Nov 26, 2003
    54
    SoCal
    Full Name:
    Asi
    Thank you all for the reassurance. You all have been very helpful.
    HAVE A HAPPY AND SAFE NEW YEAR...
     
  9. ze_shark

    ze_shark Formula 3

    Jul 13, 2003
    1,270
    Switzerland (NW)
    I think i am a candidate for tensioner bearings, can clearly tell the difference between the whine of the air pump (which has been there since the beginning), and these high pitched scringing noise which i can hear when the engine idles for the first time while coming out of my garage.
    Questions:
    - which belt tensioner are we talking about ?
    - can the bearing be changed without taking the engine out ?
     
  10. ART360

    ART360 Guest

    I'm told that you have to remove the engine to change the tensioners, but I'm sure that someone, somewhere has figured out how to change them. I'd post a seperate thread and ask.

    Art
     
  11. F355Fly

    F355Fly Guest

    Nov 26, 2003
    54
    SoCal
    Full Name:
    Asi

    FL355 you are correct. Just to make sure I popped the hood on a cold start and heard the noise coming from the extreme right rear side of the car. I saw the blower exactly as described by you. Thanks
     
  12. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,337
    Not quite: both routes exhaust gasses can travel have cats. The 'replaceable' cats (the big ones with the o2 sensor and the thermocouple/second 02 sensor) are of the ceramic 3-way variety, whille the cats welded into the y-pipe are metalic cats (probably also of 3-way configuration). There is no path from the combustion chanber to the outside world that does not pass through a cat.
     

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