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Thread: Squealing sound from engine compartment

  1. #1
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    Squealing sound from engine compartment

    Did take out my 850i -92 from winter storage a few weeks ago. Did check all various fluid levels and found that the hydraulic oil was low so I filled it up. Then when driving there is a squealing sound that occurs randomly and lasts for a second or two. It even happens when the car is parked with the engine idling. I don't know what this is and need help??

  2. #2
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    When my car does that, it's because the Pentosin fluid level is low or there's air in the system. Otherwise, all the belts are okay and not slipping...?

  3. #3
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    Thank you Chris, air in the system. Has not checked that, will do.Before putting the car to winter sleep I did change the brake fluid, that is about 6-7 months ago. I never checked the hydraulic fluid at that time. Now, reading about how to bleed the hydraulic system I realize that my car has ASC+T which demands the disconnection of its control unit. Where is it placed?
    Last edited by peake; 05-30-2018 at 06:11 AM.

  4. #4
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    I have asc+t and never heard of disconnecting anything, i always use the nipple to bleed the system. Interested to hear if there is some other steps i need to follow.

  5. #5
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    The CHF11S (Pentosin) circuit is separate to the brake system - and that is bled by turning the steering to full lock (left and right) a few times.....
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  6. #6
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    Idler pulleys

    Quote Originally Posted by peake View Post
    Did take out my 850i -92 from winter storage a few weeks ago. Did check all various fluid levels and found that the hydraulic oil was low so I filled it up. Then when driving there is a squealing sound that occurs randomly and lasts for a second or two. It even happens when the car is parked with the engine idling. I don't know what this is and need help??
    Have you checked the idler pulleys?

  7. #7
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    The pulleys are brand new.

  8. #8
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    Now I have removed all air in the hydraulic oil system. It took several tries were I turned the steering wheel, with the engine running, from left to right extremes. At the end it only came clear oil. The squealing is gone but what is more remarkable is that the ABS, ASC and +T works like they never did before. I also checked the ASC "stomp" code and it did show a funny error in the beginning ( code 17 error). After a test run it shows code 1 meaning no error. I'm happy.

  9. #9
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    Great news!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  10. #10
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    Even better news, today I found the real cause of the noise. It was the A/C and probably the expansion valve that makes the noise which has been absent since the last time I wrote in this thread. Today it showed up again but this time when I turned the A/C on. It disappeared in the same second as I turned it off again. Why it does this I don't know.

  11. #11
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    Now I have found out the origin of the noise. It was in the A/C system but not the expansion valve as I guessed from the beginning. It is the auxiliary pump, pumping hot cooling fluid into the A/C machinery. This it does to heat up the cooled air coming in from the first stage in the A/C system to let the output air have the right temperature compared with the temperature setting on the control unit. My A/C and therefore my auxiliary pump has not been working for many years (> 6) and because of that the pump was not "lubricated" and made all the noise. But after a couple of thousand kilometers it slowly stopped. The A/C is now working and keeps the temperature fairly constant. But at the same time I am worried that the pump is broken!? How can I check that the pump is ok?

  12. #12
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    Here's some info - I've done without an auxiliary water pump for many years now:

    https://www.meeknet.co.uk/e31/AuxPum...mp_Repairs.htm

    https://www.meeknet.co.uk/e31/E31_He...eplacement.htm
    Last edited by Timm; 07-18-2018 at 08:19 AM.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  13. #13
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    Quote Originally Posted by razman850 View Post
    I have asc+t and never heard of disconnecting anything, i always use the nipple to bleed the system. Interested to hear if there is some other steps i need to follow.
    https://www.bmwtechinfo.com/repair/main/721en/index.htm
    go to the Brakes section in the Contents page, then look for the ASC+t bleeding (7 lines from the top) and click it. Read here how you need to disconnect the harness to the module/unit, which is under carpet, under left door sill. TIght area but doable.
    I swear, my cars are like a girlfriend.
    Sometimes its a rough ride, sometimes its smooth motorin'.
    Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
    BUT at the end of the day, she loves it when I am inside her.

  14. #14
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    Quote Originally Posted by Timm View Post
    The CHF11S (Pentosin) circuit is separate to the brake system - and that is bled by turning the steering to full lock (left and right) a few times.....
    Do you have more info on this?

  15. #15
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    Quote Originally Posted by tangcla View Post
    Do you have more info on this?
    https://www.bmwtechinfo.com/repair/main/721en/index.htm

    Go to Chapter 32 - Steering, sub-chapter 32-13-006
    Last edited by kiwiCSi; 07-22-2018 at 10:51 PM.
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  16. #16
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    Quote Originally Posted by tangcla View Post
    Do you have more info on this?
    and if you have the asc+t then you have to bleed the pentosin system using the bleeder screw in engine bay with the ASC+t module unplugged (interior, left side, under door sill) as explained in the link I posted a few comments up.
    I swear, my cars are like a girlfriend.
    Sometimes its a rough ride, sometimes its smooth motorin'.
    Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
    BUT at the end of the day, she loves it when I am inside her.

  17. #17
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    What happens if you don't unplug the ASC+T module when you bleed the pentosin circuit?

  18. #18
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    Nothing as far as I know - I've always bled the power steering system by running the steering from lock to lock a few times:

    https://www.meeknet.co.uk/e31/BMW_E3...ter_Change.htm
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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