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Thread: Main Journal Bearing Failure

  1. #1
    Could these bearings have failed due to Overheating of the engine ? We unknowingly ran the engine with a very lean AFR during initial dyno runs . Or could this have been caused due to donuts without a dry sump ?

    http://i1136.photobucket.com/a...ghsehra/DSC03049.jpg

    http://i1136.photobucket.com/a...ghsehra/DSC03048.jpg

    http://i1136.photobucket.com/a...ghsehra/DSC03050.jpg

    -
    Inder Sehra
    Orion Racing India 2010

  2. #2
    Could these bearings have failed due to Overheating of the engine ? We unknowingly ran the engine with a very lean AFR during initial dyno runs . Or could this have been caused due to donuts without a dry sump ?

    http://i1136.photobucket.com/a...ghsehra/DSC03049.jpg

    http://i1136.photobucket.com/a...ghsehra/DSC03048.jpg

    http://i1136.photobucket.com/a...ghsehra/DSC03050.jpg

    -
    Inder Sehra
    Orion Racing India 2010
    -
    Inder Sehra
    Powertrain 2008-10
    Orion Racing India

  3. #3

    Join Date
    Sep 2005
    Location
    Washington University in St. Louis
    Posts
    55
    The pictures you posted show an issue with oiling. Just running lean or hot by itself wouldn't cause the heat buildup that those bearings show. Overheating could have thinned the oil out enough so that you weren't making good oil pressure, and inversely you could have been trying to run too much speed/load before the engine was properly warm. You could have been running over the engines advertised redline, which compromises the required oilfilm. Oil starvation also could cause it, be it from a clogged oil rifle/drilling, from a plugged filter, or from long steady-state turns like on a large skidpad. I don't see too many scratches from debris or contaminants in the oil, so thats good. Do you have any record of oil pressure from the last 30 minutes or so that you ran? What caused you to notice a problem and shut the engine down?

  4. #4
    More than likely the donuts. The oil was probably pinned to the side of the pan and the pick up wasn't able to deliver it to the pump.

  5. #5
    What does the crank journal look like?

    Ditto. Looks like an oil pressure / delivery problem to me, good thing you caught it in time. Were there a lot of hours on that engine?

    Make sure you check the timing chain components, and the camshaft bearing journals too. If you were running an engine oil cooler you should back-flush it with solvent to make sure you get any metal out that may have been washed in.

    Looks like it wasn't running without oil pressure, at least very long since you didn't get too much heat and it didn't start to gall up and spin the bearing shells.


    Drew
    _______________________________________

    Northwestern Formula Racing Alum
    Head Engineer, Frame/Suspension 2006-2009

    My '73 Saab 99 Road Race Build

  6. #6
    Which bearing is this, and are all of the others similarly effected?
    EX-FSAE

  7. #7
    Running lean will cause elevated coolant temps, dangerous EGTs, and earlier knock, but I haven't heard of it burning main journal bearings. Like the others say, oil starvation was probably the issue. If all the journal bearings are nuked, then the starvation occurred at the pressure pump pickup (AKA, dry sump tank ran dry), or a main gallery was blocked.

    Either hoon less (yeah, right )or run more oil in the sump tank. What is your system's reserve capacity?
    "The highest happiness of man is to have probed what is knowable, and to quietly revere what is unknowable."
    -Johann Wolfgang von Geothe

  8. #8
    Senior Member
    Join Date
    Aug 2009
    Location
    Kannapolis, NC
    Posts
    382
    yeah, that looks like they got a bit hot, most likely from oil starvation as others have mentioned.

    Though those dont really look that bad to me. definitely not good, but seen worse
    Any views or opinions expressed by me may in no way reflect those of Stewart-Haas Racing, Kettering University, or their employees, students, administrators or sponsors.

  9. #9
    @Faterooski

    We didn't use an oil pressure sensor , just the OEM Oil Pressure Switch . We were running the engine on the stock ECU during the donuts , so I have no record . We used the M400 on the dyno , but never saw a low oil pressure warning . We never ran the engine over 10000 revs on the dyno . The engine ran fine , no problems .

    @atm92484

    I am in doubt .

    @Drew Price

    The journal looks fine . I have no photographs of the journal . We had to replace the bearings with brown bearings . Will check the camshafts and flush the oil lines .

    Yep caught it in time . There was some oil leaking from the crankcase , so we opened it up and found the center bearing stuck on the crankshaft . Had to wait for the plastigauges to arrive , we don't find them in India . Bearing replacement is a pain !

    @ibanezplayer & Ockham
    Only the center journal bearing pair and the extreme one on the flywheel side . Why only these bearings , any idea ?

    @AxelRipper

    Caught them in time ...

    -
    Inder Sehra
    Orion Racing India 2010
    -
    Inder Sehra
    Powertrain 2008-10
    Orion Racing India

  10. #10
    If it was only one or two bearing pairs I'd blow the oil galley out backwards with compressed air in case there is a bit of grit or a chip or some other obstruction in there, especially considering how much you guys probably paid for that engine and how difficult it will be to get spare parts.

    Do you even have a backup engine?

    It may just have been abused before you got it, but you never know.

    Since you have Plastigage coming check all the bearings while you're in there to make an educated decision about how to proceed.

    Drew
    _______________________________________

    Northwestern Formula Racing Alum
    Head Engineer, Frame/Suspension 2006-2009

    My '73 Saab 99 Road Race Build

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