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Thread: Compression test results consultation please

  1. #1
    Join Date
    Dec 2004
    Posts
    153

    Default Compression test results consultation please

    Hello all,
    Hope you've done all your Christmas shopping! Have a great Holiday!
    I've done the compression test on my 1989, m20, 525, 130k milesi and not sure how to interpret it. Here's what I've got on the first test:
    Cranked 3 times and got around 165PSI, exept the # 6 was 176
    I did the test second time to make sure and cranked 6-7 times to maxout the pressure and it showed 185 on 1,5th 180 on 2,3,4 and and 220 on the 6th plug.

    Is the compression for # 6, the one closest to firewall, a problem and what kind . Is my compression too high? I could I do to remedy it?
    Thanks

  2. #2
    Join Date
    Jan 2004
    Posts
    4,150

    Default Try it one more time disabling the ignition and the fuel pump and hold the

    throttle wide open while cranking



    Quote Originally Posted by nariusb
    Hello all,
    Hope you've done all your Christmas shopping! Have a great Holiday!
    I've done the compression test on my 1989, m20, 525, 130k milesi and not sure how to interpret it. Here's what I've got on the first test:
    Cranked 3 times and got around 165PSI, exept the # 6 was 176
    I did the test second time to make sure and cranked 6-7 times to maxout the pressure and it showed 185 on 1,5th 180 on 2,3,4 and and 220 on the 6th plug.

    Is the compression for # 6, the one closest to firewall, a problem and what kind . Is my compression too high? I could I do to remedy it?
    Thanks


  3. #3
    Join Date
    Dec 2004
    Posts
    153

    Default

    Quote Originally Posted by Bill R.
    throttle wide open while cranking
    Thanks Bill, I did. I took the main and fuel relays out and depressed the pedal to the ground while cranking. I also put a teaspoon of oil in first.
    The Bentleys are saying it should be142 to 156 after 2/3 cranks. Mine is a bid higher. It would't bother me but the sixth cylinder is higher by 10 PSI after 3 cranks and by 35PSi after 6 cranks.
    I also have oil leak somewhere in the area of the sixth cylinder. Could a leak cause this?

  4. #4
    Join Date
    Feb 2004
    Posts
    4,894

    Default

    The readings look good... engine in good condition. The sixth cylinder may have carbon deposit due to oil leak... which takes up space in cylinder and causing higher pressure reading. You need to decoke this cylinder and fix the oil leak which is most likely to be cause by valve seals.

  5. #5
    Join Date
    Dec 2004
    Posts
    153

    Default

    Quote Originally Posted by Tiger
    The readings look good... engine in good condition. The sixth cylinder may have carbon deposit due to oil leak... which takes up space in cylinder and causing higher pressure reading. You need to decoke this cylinder and fix the oil leak which is most likely to be cause by valve seals.
    Thank you, Tiger
    Thats a relieve! Could you specify when you say valve seals, please. Let's say I take valve cover, should I did deaper, what seals should I look for there?

  6. #6
    Join Date
    Aug 2005
    Location
    east anglia uk
    Posts
    266

    Default

    Quote Originally Posted by nariusb
    Thank you, Tiger
    Thats a relieve! Could you specify when you say valve seals, please. Let's say I take valve cover, should I did deaper, what seals should I look for there?

    part number 19

    its a head off job im afraid
    Attached Images Attached Images  
    Last edited by bullyd; 12-19-2005 at 03:40 PM.

  7. #7
    Join Date
    Dec 2004
    Posts
    153

    Default

    Quote Originally Posted by bullyd
    part number 19

    its a head off job im afraid
    Thanks again for input. It drives well. Can I keep on driving with the hi 6th cylinder compression or should I fix it promptly. How extensive is the repair?

  8. #8
    Join Date
    Dec 2003
    Location
    Eastern Tennessee USi
    Posts
    14,839

    Default

    the lash could be off in that cylinder, or excess ould can cause a higher reading from a better seal on the rings.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  9. #9
    Join Date
    Dec 2003
    Location
    Central NJ - USA
    Posts
    1,540

    Default

    u could try a leakdown test as well to make sure

  10. #10
    Join Date
    Dec 2004
    Posts
    153

    Default

    Quote Originally Posted by 632 Regal
    the lash could be off in that cylinder, or excess ould can cause a higher reading from a better seal on the rings.
    Hi Regal,
    When you say lash could be off, do you mean I need valve udjustment and it would cause higher compression in one cylinder? Should I just follow Bruno's instructions: http://www.bmwe34.net/e34main/mainte...lve_adjust.htm
    Thanks

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