Rod knock, oil analysis, next steps?

Discussion in 'Generation 4 - Maintenance & Troubleshooting' started by ShoMe1More, Nov 7, 2018.

  1. ShoMe1More

    ShoMe1More New Member

    Joined:
    Mar 25, 2012
    Messages:
    22
    Likes Received:
    1
    Location:
    NY
    Been having a rod knock for a over year, trying to nail down a solution.

    Oil analysis came back from blackstone labs (see picture attached). Looks like a good bit of iron content , so the crank is probably scored. Definitely needs rod bearing replacement.

    Two options:
    1) Replace just the bearings without having to pull whole engine (less $ and labor). Do these engines suffer from a scored crank journal if the bearings are new, or can they survive and tough it out?
    2) Replace entire shortblock with a upgraded high performance option and use rest of existing engine. If the issue is rod bearings and crank wear, would the rest of the upper part of the engine be OK to use married with a beefed up short block?

    What do you all think?
     

    Attached Files:

  2. luigisho

    luigisho SHO Member

    Joined:
    Nov 2, 2001
    Messages:
    8,014
    Likes Received:
    1,150
    Location:
    va beach,va
    Home Page:
    You have to examine it closely to see what the damage looks like. After a year.... How long you plan on keeping this thing? over a yr. you need to crunch the numbers and get non damaged internals either in part or whole (shortblock). Again get a good look at the bearings, the end of the rod/caps and the crankshaft.
     
  3. ShoMe1More

    ShoMe1More New Member

    Joined:
    Mar 25, 2012
    Messages:
    22
    Likes Received:
    1
    Location:
    NY
    I plan on keeping it for a couple more years. The real question is to save the $$ and just do the minimum fix (rod bearings).

    The problem with inspection is $$$, just to tear it down to examine the rod bearings is being quoted at 8 labor hours. If the crank needs to be replaced. That is a different job of taking the engine out (15 hours).

    That's why I'm seeing if it is possible to just replace bearings even with some wear on the crank journal and still get some decent durability out of the engine?
     
  4. luigisho

    luigisho SHO Member

    Joined:
    Nov 2, 2001
    Messages:
    8,014
    Likes Received:
    1,150
    Location:
    va beach,va
    Home Page:
    You take your chances and the answer is 'depends' but usually that is a shorter term fix than you expect and you're back to square 1. Sometimes you get lucky but I never get that lucky. There is no way to even make a good guess without examining it.

    The surest outcome is new shortblock, also the most expensive. Well maybe replacement crank and rod/s with labor might cost more. In the end the risk is yours as is the money. You have to make the call.
     
  5. 6500rpm

    6500rpm Quality Always Shoots Straight

    Joined:
    Jun 21, 2016
    Messages:
    291
    Likes Received:
    307
    Gender:
    Male
    Occupation:
    Journeyman Fleet Tech
    Location:
    The safe zone outside metro St Louis
    Just curious why you think it's a rod knock? If you do any amount of driving at all I've never seen a rod bearing clearance issue that didn't go terminal fairly quickly. Do you have any dtc's setting? Do you know what cylinder has the problem (you can isolate it most likely by just unplugging each coil one by one and listening for a change in the knock as the cylinder pressure is taken away). Does it knock when cold and go away as the engine warms up (piston slap). The Blackstone report definitely shows that you have some sort of mechanical issue going on inside, but man it's hard for me to believe that with the load put on a rod under fire that it could have held on for a year. Hopefully John bigdog will chime in too.
     
    SHOdded likes this.
  6. krewat

    krewat SHO Member

    Joined:
    Dec 20, 2012
    Messages:
    644
    Likes Received:
    568
    Occupation:
    System Administrator
    Location:
    Long Island
    Home Page:
    In my way of thinking, if you have a rod knock, it's already too late.

    What other substances are in the analysis that would correspond to a rod bearing being wasted? Scoring the crank is one thing, but if it's scored, well, the bearing would be toast as well and would show up in the analysis I would think.

    The real question is if the rod journal is even across the face anymore. A score, meh, but if the journal is worn at all, it's not worth it.
     
    SHOdded likes this.
  7. sperold

    sperold Last to Know

    Joined:
    Aug 25, 2008
    Messages:
    3,309
    Likes Received:
    1,041
    Gender:
    Male
    Occupation:
    Mech. Tech.
    Location:
    Ontario Canada
    When is your "knock" the loudest, at startup or when hot?

    Any smoke or other noises?

    You could try individually removing plug wires while idling to see if the phantom noise stops when a certain cylinder is no longer firing. That would tend to strengthen the case for a bad rod bearing.

    If you can do the labor yourself, pull the pan, manually polish the crank and install new rod bearings only.

    It could be a wrist pin / piston issue, so the crank remedy is an educated guess, but still a gamble.

    If that is not possible, pay to swap in a complete replacement engine (used) with some good credentials.
     
    SHOdded and krewat like this.
  8. ShoMe1More

    ShoMe1More New Member

    Joined:
    Mar 25, 2012
    Messages:
    22
    Likes Received:
    1
    Location:
    NY
    I was getting misfires intermittently since day 1 purchasing the vehicle. The trouble codes were showing a cylinder overboost issue if I can recall correctly. Recently had all the plugs swapped (one was toast) and one coil pack was aftermarket, so switched that to motorcraft. Haven't had a misfire since.

    It knocks cold and warm. Louder at warm.

    It is an interesting point a few of you guys have made regarding the engine typically not tolerating a rod issue for over a year. This February will be 2 years since the noise first showed up under a heavy load. The noise also only begins after 2.5k-3k rpms and greater.
     
  9. ShoMe1More

    ShoMe1More New Member

    Joined:
    Mar 25, 2012
    Messages:
    22
    Likes Received:
    1
    Location:
    NY
    To answer how it was determined to be a rod knock. Mechanic used stethoscope and showed me how loud the noise was at the oil pan vs the top of the engine. Is this not the only thing that could be making that noise at the oil pan and increases speed/loudness along with rpm?
     
  10. luigisho

    luigisho SHO Member

    Joined:
    Nov 2, 2001
    Messages:
    8,014
    Likes Received:
    1,150
    Location:
    va beach,va
    Home Page:
    A scope is a good way to track that down
     
    SHOdded likes this.

Share This Page

If you wish to help keep SHOforum running, please click the donation button below