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Detroit 671

Discussion in 'Engines' started by Gerdie, Aug 14, 2015.

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  1. Gerdie

    Gerdie Member

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    The starboard engine decided to burn through a quart of oil an hour. I noticed some oil leaking from the bottom of the turbo. After some thought, if the turbo is pushing oil into the cylinders from a bad seal, could the seals be replaced or is it a new turbo? Any thoughts before I go the rebuild route? Any help would be appreciated.
  2. Capt Ralph

    Capt Ralph Senior Member

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    Lets start with what you have.
    671TI, 671TIB? Hours and when did this start?
    What color is your exhaust? Engines come up to speed?
    Do you have an air box drain? Capture can? What's in it?
    How 'bout crank pressure, valve cover vent blowing lots of oil mist?
    Turbo, Blower seals, Rings could be candidates.
    The more we know, the better we can help.
    ,rc
  3. Capt J

    Capt J Senior Member

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    It could be simply leaking from the oil drain hose on the turbo. Not enough info to really diagnose.
  4. K1W1

    K1W1 Senior Member

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    It could also be oil that is carried over from the breather if it is connected to the inlet and has condensed out.
  5. Gerdie

    Gerdie Member

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    Sorry for the slow response, usually I get email notifications saying someone has posted.

    They are 671-TI. 1986 with 2,040 hrs. The starboard engine is able to maintain 2,000 rpm at normal speed. I have not tried pushing above 2,000. Exhaust smoke has a blue tint to it. If I run the boat for five hours it burns five quarts, 8 hours 8 quarts.

    This all started when smoke started coming out of the can located about eight inches (air box ?) off the engine. The mechanic couldn't isolate the problem so he reversed the hoses back into the engine to push the smoke out of the exhaust. The boat ran fine it just burns a quart of oil an hour and the blue smoke seems to be getting worse.
  6. Capt Ralph

    Capt Ralph Senior Member

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    Are they any real mechanics in your area?
    Or at least somebody that understands a little about Detroits?

    The first can I can think of is the air box drain. If it's full, it may blow oil and oil may back up in the air box.
    But 1 qt a hour is not good.
    Next can could be the Air-Sep system. But I'm still guessing here.
    A picture would help and a pic of the mod.

    When we find you a mechanic, the air box drain needs to be checked for excessive oil. That may help determine if it's blower or turbo oil seals. I am feared the side covers need to come off and the piston rings examined.

    One of the Post kids had some blower work just done and he may have some comments to share. I think that was internal oil leaking related.
  7. Gerdie

    Gerdie Member

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    We have not located a good Detroit mechanic yet. This is our first set of diesels so we are learning a quickly as possible. We have noticed Detroit guys seems to be a dying breed.

    Let me work on photos shortly. Again, thanks for your help.
  8. YachtForums

    YachtForums Publisher/Admin

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    Gerdie,

    Please resize your images as per our rules. No larger than 640 pixels. Your pics were over 3000 pixels, therefore removed.
  9. Capt J

    Capt J Senior Member

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    Have you tried calling the Detroit dealer? I'm sure they could work on it. It sounds to me like you have broken rings on 1 cylinder. That would be the most likely suspect I would think.
  10. Gerdie

    Gerdie Member

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    Did the photos upload as bad as they look? I'll need to learn a better way to post pics.
  11. Capt Ralph

    Capt Ralph Senior Member

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    I'm just getting the hang of getting the picture size down myself. Using a photo editor, you have to change the stretch/skew or properties down to no more than 640 pixels wide.

    Or, I'm going to send you a direct message thru the system. It will include my direct e-mail address. Send the pictures to my direct address, I can resize them and post them.
  12. Capt Ralph

    Capt Ralph Senior Member

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    We received the pictures, downsizes them to 25%.
    2015-08-13 07.23.43a.JPG 2015-08-16 19.41.57a.JPG 2015-08-16 19.41.15a.JPG
  13. Capt Ralph

    Capt Ralph Senior Member

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    It looks like a remote crank vent bottle. Old Racor (or like) stuff.
    Crankcase pressure and fumes would normally blow thru this and back into the air filter. Gelled oil would be reclaimed and deposed of.
    The other lines would be air box drains.
    Newer crank vents would return the oil. With air box slobber, you don't want this oil reused.
    Has anybody serviced these bottles (cans)? Drain or pour the oil out of them?

    The guy you had bypass it, probably directly connected the crank hose to the air inlet, it would then be consumed and then out the exhaust.
    Question;;;; Was the exhaust blue before this mod? Probably not.
    You have some crank case pressure issues.

    What oil (brand, weight, API rating) is in the engine?
  14. Gerdie

    Gerdie Member

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    I have been running straight 40w rotella. The pressure has been good. The boat never lost rpm or speed. No smoke prior to the mod, starboard burned a quart a day. The air boxes have not been checked. If I drain the cans will that tell me how much oil is being pushed out the engine?
  15. Capt Ralph

    Capt Ralph Senior Member

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    That's Rotella T1, with an API CF-2 in a 40W?
  16. Gerdie

    Gerdie Member

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    I think so. Straight 40w is not stocked in most stores. I have tried to stay consistent with Rotella. At a quart an hour I'm searching for five gallon pales at this point.
  17. Capt Ralph

    Capt Ralph Senior Member

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    I suspect a washed cylinder or two resulting in some excessive crank case blow by. Lets clean up that crank vent, get an oil sample sent in to an oil lab and give our forum a chance to check in. Some of these kids are on the other side of the world (and then some).. Then some have a real job and it takes longer to check in.
    In the mean time, you may need to start some looking into a real Detroit mechanic or a dealer.
    2-stroke Detroits have only been around for over 70+ years. Gotta be an ole Detroit fart in your area.
  18. Capt Ralph

    Capt Ralph Senior Member

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    A NAPA store can sell you what I use. Part number 75118. This is CF-2/40w approved oil.
    Last edited: Aug 17, 2015
  19. Gerdie

    Gerdie Member

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    The quest is on for a Detroit Diesel die hard who just can't give it up yet. I will start turning over rocks and hopefully I can find this mechanic who wants to take a look in one more engine room.

    Any advice on what not to do as far as mechanics who just want to start taking things apart?
  20. Capt Ralph

    Capt Ralph Senior Member

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    As I stated earlier, there are inspection covers that allow checking the piston and rings, watching the air box drains is also a good indicator.
    This will take a few hours but will offer a better guide as to whats really going on.

    When you know whats really going on, then it can be fixed smartly.

    Always get any activity in writing from a reputable shop.
    Last edited: Aug 17, 2015