RM European Auto Parts
Results 1 to 10 of 10

Thread: Brainstorming: E39 M5 misfire/poor leakdown on one cylinder

  1. #1
    Join Date
    Sep 2007
    Location
    New York
    Posts
    2,108
    My Cars
    1974 2002, 2009 128i

    Brainstorming: E39 M5 misfire/poor leakdown on one cylinder

    I passed by my indy's shop today and was chatting with one of the techs about an E39 M5 he had on the lift with the right side cylinder head on the bench. Apparently it suffered a timing chain guide failure, which was repaired without incident, but running post-repair showed a misfire on #3. They did a leakdown test that confirmed a problem on that cylinder only. The #3 cylinder wall, piston, combustion chamber, and valves all look untouched and functionally identical to the others on that bank. Head gasket was normal and consistent in appearance across the bank. Valves seem to be sealing properly (he had the intake ports full of water when I was there, and the combustion chamber side was dry; exhaust was the same) At this point they were planning to send the head out to check the casting for microscopic cracks.

    While I'm deeply glad that this is not my car, as I hate chasing weird problems when I just want to drive the thing, as an academic exercise I'm curious. Any thoughts about what might be going on? Ever seen something like this?





    Life's tough. It's tougher when you're stupid.
    -John Wayne

  2. #2
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    Hi Andrej,

    I don't know if you remember my M5 misfires, and the incredible saga I had, chasing them:

    https://www.bimmerforums.com/forum/s...526-DME-Repair

    I had leak down on one of the cylinders; but not the other. I took a chance, and listened to my boss (a Premier Master Porsche Tech), and used a wooden dowel and a hammer to thump the lifters, to attempt to free sticky lifters.

    All in all, I replaced plugs, coils, had the injectors blueprinted, replaced all the lifters, the engine wiring harness. I did leak down tests, compression tests, smoke tests.....don't even remember everything.

    Interestingly, the leakdown KEPT showing up on cylinder 2, until I finally found the cure : A new DME, from a used M5, virginized and mated to my EWS by Abel, including moving my tune to the new computer. No more misfires. My guess is that the coil drivers on 2 and 8 were dying?

    If the shop has already tried all the basics, and still has misfires, they might want to try a DME. Although I NEVER suspect the DME, for some reason, I did, when I first started that thread. Nonetheless, I tried EVERYTHING else first.

    Personally, after my own experience with my M5, I take leakdown tests with a grain of salt.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  3. #3
    Join Date
    Sep 2007
    Location
    New York
    Posts
    2,108
    My Cars
    1974 2002, 2009 128i
    Thanks, Chris. I have only the vaguest of recollections of your misfire issues - my brain is quite schizophrenic when it comes to deciding what information to retain and what to discard, so please don't take it personally. It certainly sounds like an avenue to explore. I'll pass along your thread to them - hopefully it will help out.





    Life's tough. It's tougher when you're stupid.
    -John Wayne

  4. #4
    Join Date
    Sep 2006
    Location
    NW suburban Chicago
    Posts
    16,302
    My Cars
    hiss by my window
    I still don't understand how an electronic issue can be responsible for leakdown. Cylinder washing from over fueling, yes but enough to permanently cause leak down and then to be corrected with electronics ? I can see why you might discount LD results.

    Cracks, "microscopic" ones certainly, ain't the issue. If significant enough in block or head as to effect cylinder pressure you'd already know.
    I wonder if the subject of this thread hasn't got a sticky ring.
    Last edited by ross1; 07-19-2018 at 12:04 PM.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  5. #5
    Join Date
    Dec 2013
    Location
    Chicagoland area
    Posts
    4,372
    My Cars
    EXOTICS
    From what I remember of that interesting thread,
    is that misfires kept showing up on cylinder#2.
    I don't recall leakdown test failures,
    but then again my memory isn't what it used to be.

  6. #6
    Join Date
    Jun 2002
    Location
    Aberdeen, NC (yes, again)
    Posts
    23,672
    My Cars
    E39M5, E500 4WD
    https://www.bimmerforums.com/forum/s...E-Repair/page5

    See post 115.

    I don't have the slightest idea why the electrical / DME issue and the leakdown results correlated....ON ONE CYLINDER, (not both) for a while.

    The anomalies of my own M5's issues were enough to convince me that we have to think beyond the box sometimes. (Note please that the very same car continues to torment me with blatantly simple brake issues.)

    You all know the story of the plumber's pipes always leaking?

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  7. #7
    Join Date
    Dec 2013
    Location
    Chicagoland area
    Posts
    4,372
    My Cars
    EXOTICS
    Yes Chris, thanks for the refresher course,
    I ended up reading from post#115 all the way till the end.(post#177)

  8. #8
    Join Date
    Mar 2007
    Location
    Middle of a corn field
    Posts
    14,770
    My Cars
    E39 hamster/ruberbandPWR
    Quote Originally Posted by ross1 View Post
    I still don't understand how an electronic issue can be responsible for leakdown. Cylinder washing from over fueling, yes but enough to permanently cause leak down and then to be corrected with electronics ? I can see why you might discount LD results.

    Cracks, "microscopic" ones certainly, ain't the issue. If significant enough in block or head as to effect cylinder pressure you'd already know.
    I wonder if the subject of this thread hasn't got a sticky ring.
    If the piston rings are sticking, wouldn't the pistons / piston wall show some yuckiness ?

    O2pilot,
    You got rid of your E39 ?

    Looking for an E39 belly pan , passenger front inner fender liner …

  9. #9
    Join Date
    Sep 2007
    Location
    New York
    Posts
    2,108
    My Cars
    1974 2002, 2009 128i
    Quote Originally Posted by Jason5driver View Post
    O2pilot,
    You got rid of your E39 ?
    Yeah, exactly a year ago. Ten years and 100k miles in my care (200k total), it was time to move on. Sold it to a friend of mine who is enjoying it. I'm in an 09 128i M-Sport now.





    Life's tough. It's tougher when you're stupid.
    -John Wayne

  10. #10
    Join Date
    Sep 2006
    Location
    NW suburban Chicago
    Posts
    16,302
    My Cars
    hiss by my window
    Quote Originally Posted by Jason5driver View Post
    If the piston rings are sticking, wouldn't the pistons / piston wall show some yucki
    No , not necessarily.
    I'd be curious to know if it was smoking or using oil. What does the plug out of that hole look like?

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

Similar Threads

  1. E39 M5 sporadic misfires, no crank
    By bmwdirtracer in forum General BMW Mechanical Help sponsored by RM European Auto Parts
    Replies: 8
    Last Post: 10-01-2016, 10:28 AM
  2. M5 E39 99- Misfires
    By tomtebloss in forum 1996 - 2003 (E39)
    Replies: 17
    Last Post: 08-10-2015, 12:05 PM
  3. E39 - M5 2003 - Misfire fault
    By Thalonius in forum 1996 - 2003 (E39)
    Replies: 24
    Last Post: 02-01-2010, 12:00 AM
  4. E39 FS: e36 (e39 M5 Style) Mirrors
    By TIATO in forum Exterior Lighting & Body Parts
    Replies: 4
    Last Post: 02-15-2007, 11:52 AM
  5. E39 E39 M5 Mirrors
    By ///M297 in forum Exterior Lighting & Body Parts
    Replies: 3
    Last Post: 02-07-2007, 10:02 AM

Bookmarks

Posting Permissions

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