Results 1 to 15 of 107

Thread: 1994 K75S High-pitched chirping noise when hot?

Hybrid View

  1. #1
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085

    1994 K75S High-pitched chirping noise when hot?

    I'm getting an intermittent but fairly loud high-pitched chirping noise from somewhere under the tank when the bike gets hot.

    The radiator fan seems to be working OK and the chirping is independant of that; only thing in common is that it only occurs when the bike is running hot (now living here in Albuquerque that is much more often than my previous location where I first noticed it several months ago).

    I suspect a bearing somewhere; perhaps the water pump is acting up?

    If anyone can shed some light on what my problem might be that would be great. Hopefully it's nothing serious, but...

    Regards, Jeff
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  2. #2
    A bozo on the bus deilenberger's Avatar
    Join Date
    Mar 2003
    Location
    Spring Lake NJ, USA
    Posts
    7,736
    Jeff - your best bet - visit a Harbor Freight and purchase a mechanic's stethoscope. That should let you localize it.

    "Under the tank" is a wide expanse of territory to guess where the noise is coming from. It could be anything from a bearing going bad somewhere, to the a plugged fuel filter (the fuel pump has a blow-off valve that chirps when it's pushing against too high a resistance.)

    Try to narrow it down a bit and get back to us with your findings.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  3. #3
    A bozo on the bus deilenberger's Avatar
    Join Date
    Mar 2003
    Location
    Spring Lake NJ, USA
    Posts
    7,736
    Quote Originally Posted by deilenberger View Post
    Jeff - your best bet - visit a Harbor Freight and purchase a mechanic's stethoscope. That should let you localize it.

    "Under the tank" is a wide expanse of territory to guess where the noise is coming from. It could be anything from a bearing going bad somewhere, to the a plugged fuel filter (the fuel pump has a blow-off valve that chirps when it's pushing against too high a resistance.)

    Try to narrow it down a bit and get back to us with your findings.
    http://www.bmwmoa.org/forum/showpost...68&postcount=2

    Hmmm... this was the very first answer to your original posting..

    Think about how much time/$$$ could have been saved..
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  4. #4
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    Right you are, Don. In my dilemna and advancing age I got sidetracked by the blocked fuel return line and actually forgot about the stethoscope until Ted piped in about it later on. I am getting a bit more senile at age 61 than I would have expected (absent-minded more than ever lately; I think my 88 year-old dad is sharper than I am!

    Oh, well, at least I have an almost completely new fuel system going and the bike is running great otherwise (and I didn't damage anything important by operating the bike while screeching; it was only a fan motor bearing).

    I just noticed that Beemerboneyard sells just the fan motor (Bosch!) for $79 so I immediately ordered one minutes ago. Now I'll look into what I need to remove in order to install it asap...

    Thanks again for your help and I'm sorry I spaced out acting on your excellent advice.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  5. #5
    Themason 42906's Avatar
    Join Date
    Jan 2007
    Location
    Ridgecrest California
    Posts
    444
    Quote Originally Posted by Zagando View Post
    I'm getting an intermittent but fairly loud high-pitched chirping noise from somewhere under the tank when the bike gets hot.

    The radiator fan seems to be working OK and the chirping is independant of that; only thing in common is that it only occurs when the bike is running hot (now living here in Albuquerque that is much more often than my previous location where I first noticed it several months ago).

    I suspect a bearing somewhere; perhaps the water pump is acting up?

    If anyone can shed some light on what my problem might be that would be great. Hopefully it's nothing serious, but...

    Regards, Jeff
    Just so I am on the same page with you, does it ever chirp when the fan is not running?
    Experience is what you get when you don't get what you want.

  6. #6
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    Yes, it chirps when the fan is on or off; doesn't make any difference.

    It always seems to happen when I am riding or at a stoplight and only when things are hot (ambient temps as well as the bike all warmed up in stop and go traffic.

    Maybe no need for a mechanic's stethoscope as I happen to have a medical stethoscope on hand (I was Dr. Mango Daiquiri come Halloween at my last job (bartender)). Perhaps it will come in handy again so I'll start carrying it with me when I go out on the bike.

    Thanks, guys!
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  7. #7
    Registered User kentuvman's Avatar
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    883
    FWIW, my '87 K75s whined this past week when stopped at a traffic signal with the fan trying to keep her from overheating.

    Heck, I was whining too!

  8. #8
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    Let's not confuse the whining of the fuel pump with this intermittant high-pitched chirp, please! Definitely out of the ordinary in my K-bike experience.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  9. #9
    A bozo on the bus deilenberger's Avatar
    Join Date
    Mar 2003
    Location
    Spring Lake NJ, USA
    Posts
    7,736
    Quote Originally Posted by Zagando View Post
    Let's not confuse the whining of the fuel pump with this intermittant high-pitched chirp, please! Definitely out of the ordinary in my K-bike experience.
    In case you misunderstood.. the fuel pump is capable of putting out 100PSI, until it burns up or explodes IF the output is plugged up (say by a bad fuel filter.) To prevent this from happening, it has a built in blow-off valve. That valve kicks in at about 80 PSI, and when it relieves the pressure, it sounds like a chirp. As the pump keeps running, it then sounds like a series of chirps. THAT is what I was referring to - not the normal whining noise (although that does get louder as restriction builds on the output of the fuel pump.)

    It's not a common noise - but it is a known noise. It may be out of the ordinary in your K-bike experience, but it is not out of the ordinary for everyone's k-bike experience.

    YMMV.. (but not a lot.)
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  10. #10
    Registered User naddy100's Avatar
    Join Date
    Jul 2003
    Location
    Starkville, Mississippi
    Posts
    394
    Quote Originally Posted by deilenberger View Post
    Clymers is almost right.. That's at idle with the vacuum line to the FPR connected. If you rev the engine, you'll see the pressure increase, if you disconnect the vacuum line to the FPR, (from memory) it should rise to around 42PSI (and the fuel gauge will smooth out also..) The vacuum line in question is the small hose going to the rear-most throttle body nipple on the base of the TB..
    My big learns for today are more about the fuel system, and how to get Tapatalk working!

    Thanks for the time and effort as always.
    Noel

    Sent from my Transformer Prime TF201 using Tapatalk 2

  11. #11
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    My new ABS relay arrived this morning so I thought I'd replace that at least.

    Once I had the gas tank off I examined both external fuel hoses and deemed the return line questionable enough to warrant replacement---so I called Sandia BMW at 10 minutes to 5pm on the the Friday of Labor Day Weekend.

    They had one meter of the fuel line in stock, I paid for it over the phone and dashed over in my truck to pick it up as they were closing up shop.

    Got back home and proceeded to take the bike apart so I could replace the return line as well as the main fuel line to the fuel rail.

    My wife actually came out to help me but we are currentlly stuck---we cannot get the blasted air filter out even though I removed all three spring clips and pulled out that hard air input thing that goes in on the starboard side of the air box. It doesn't want to budge! I don't want to chew it up with pliers as it's still in decent shape but I do need to take it apart so I can undo the far end of the return hose (which appears to connect in the middle of the throttle assembly if I am reading the Clymer diagram correctly).

    Maybe tomorrow (when it's light out and we can see what were doing) we'll succeed. I did replace the air filter three years ago all by myself but I still remember it being one of the worst things about working on the K75.

    So that's it for now but will report as soon as any further progress is made (fingers crossed).

    Since the fuel return line (hose) looks a bit funky I might also replace that Z-shaped breather hose and the fuel pressure regulator hose at the same time, once I eventually get to the other end of the return line when the airbox is off the bike. Probably a good idea and worth the minimal cost and hassle to go back and get the additional Z-hose on Tuesday.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  12. #12
    Dum vivimus vivamus ted's Avatar
    Join Date
    Mar 2003
    Posts
    2,589
    This has always worked for me:
    http://www.ibmwr.org/ktech/air-filter-change.shtml
    It slides out on the throttle side.

    As for the "Z Hose", that is the notorious crankcase breather hose, the cause of many a lean running condition on many K Bikes (my K75RT included.) Those things go bad every three or four years and allow unmetered air into the system resulting in all kinds of shenanigans. Mine looked fine and was only two years old, but I had a spare so I swapped it out and when I got the one on there off I realized what looked like a little dry rot was actually a crack a half the way around.

    Pics here
    http://www.bmwmoa.org/forum/showthread.php?t=56654
    Ted
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

  13. #13
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    You slide the filter out on the throttle side, Ted? Really? I'll go out and see if it looks doable by me but I remember doing from the other side the one other time I replaced the air filter.

    Or perhaps I'm misreading here. By throttle side do you mean in regards to the handlebar/throttle or to the throttle bodies which are on the opposite side? Sorry to be so dense but I'm a bit confused. Maybe I'll figure it out when I get working on it again that it's daylight (I started too late yesterday afternoon and it got dark all too soon).

    Thanks for the info, too.
    Last edited by Zagando; 09-02-2012 at 05:39 PM. Reason: typos
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  14. #14
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085

    Such good news (for the time being, at least)

    I just wrestled, pried, jiggled and wiggled the airbox and filter some more---and got the filter out at last! Came out on the starboard side of the bike as per Clymers (and Ted's) advice (realize that you meant handlebar throttle side, Ted, sorry for my confusion).

    Now I've got the bottom half of the airbox unbolted and out for a thorough cleaning and eventual reassembly---and I can now see clrearly where the other end of the fuel return line is attached for the first time in my K-bike life. Whew! What a relief!

    Now for the really good news: My crankcase breather (Z-shaped) hose is cracked!

    That is good news for me because it means that that may be the root cause of my chirping noise that has been plagueing me for some time.

    If Don, Paul, Lee or Ted or anyone else that might be reading this knows if my cracked hose assumption is correct please let me know. At the very least, my efforts to get to the fuel return line have paid off as I know that Z-hose can or will cause all sorts of other problems down the line and now I have the perfect opportunity to replace it ASAP.

    Knowing where and what the problem is feels like 90% of my battle is won!

    The only possible hitch in the immediate future (this long weekend wait for the BMW dealer to reopen Tuesday) is the fuel line that I got there yesterday is a bit smaller than my old fuel line. Since I specified that it was for a '94 K75 the parts guy probably got the right part # but I am wondering if the hose size changed at all over the years?

    At any rate, a minor detail that I can correct by getting something equivalent at Napa or Auto Zone if need be. I'll try to fit one end of this BMW hose over one of my tank's fittings beforehand and if it fits all the way on I'm still good to go.

    Further updates to follow as warranted and boy, am I relieved to be seeing a tiny ray of light at the end of the tunnel!
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •