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5.0 Ford blowing out oil under load-gctid400215

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    5.0 Ford blowing out oil under load-gctid400215

    Need some help

    I have an 1989 Bayliner Trophy with a 5.0 L Ford and OMC Cobra out drive. I just had a new long block installed and it runs great in idle and when running WOT. Problem is when WOT or under load the engine is blowing out oil somewhere. I will lose a quart in less than 5 minutes! I took it into the shop once but I can not recreate the leak on land and the mechanic could not find any sources of a leak. When on the water I can not see exactly where it is coming from either oil in the bildge and little smoke (nothing heavy maybe hitting exhaust). From what I see on the oil gage it does not look like the engine is over pressurized, but I have my doubts. This motor has breathers no PCV valve. Has spash guards in the covers.

    Couple of my thought are that they may not have torqued the oil pan or any of the other dressings when they installed. (was not impressed with this mechanic and not taking it back to them to fix for fear of further damage). So I am going to check torque.

    Could the rear main cause this?

    Could a cracked oil sending unit cause a leak this large?

    Any suggestions would be appriciated.

    #2
    First of all, we should not be operating at WOT RPM, other than for prop/gearing testing.

    WOT RPM for sustained periods will definitely shorten engine life.

    Are you sure it's an oil leak, and not oil being burned?

    Which oil pan was used on this engine?

    There were several Ford 5.0L automotive oil pans that do not work well for Marine use.

    Suggestion:

    Clean off all engine parts.

    Run up to the RPM where you believe this leak begins to occur.

    Do this for a short duration and shut down.

    With a clean cloth, wipe around all suspect areas.

    If it is a leak, it should raise it's ugly head and you'll find the location.

    If it is not leaking oil, then you may have an internal problem.

    .
    Rick E. Gresham, Oregon
    2850 Bounty Sedan Flybridge model
    Twin 280 HP 5.7's w/ Closed Cooling
    Volvo Penta DuoProp Drives
    Kohler 4 CZ Gen Set

    Comment


      #3
      It is under load that the engine would burn the most oil. It sounds like something went wrong with the rebuilt. A compression test might show something. Since the exhaust is under water there wouldn't really be any smoke.

      Comment


        #4
        Engine is not smoking at all or burning oil. When on shore and hooked up to the muffs no oil leak. When in the water and idle or low rpm no oil leak. When under a load oil fills up the bilge pretty quickly.

        do not know which oil pan it is from. Came off of the previous engine and it did not leak on that one.

        My two theories are:

        One I am getting over pressure in the case

        Two. Installer did not torque dressings (oil pan valve covers) to spec.

        Thoughts?

        Comment


          #5
          marine wrote:
          ..............When under a load oil fills up the bilge pretty quickly.

          My two theories are:

          One..... I am getting over pressure in the case.

          Two..... Installer did not torque dressings (oil pan valve covers) to spec.
          Over pressure as in crankcase pressure?

          Excessive oil pressure would not cause this, and is unlikely, IMO.

          An oil pan gasket would not necessarily require being under load in order to leak.... unless it's from excessive crankcase pressure.... perhaps from a bad piston ring(s) seal.
          Rick E. Gresham, Oregon
          2850 Bounty Sedan Flybridge model
          Twin 280 HP 5.7's w/ Closed Cooling
          Volvo Penta DuoProp Drives
          Kohler 4 CZ Gen Set

          Comment


            #6
            It could be the attitude of the boat. When you take off and the bow rises the oil goes to the back of the engine. If the oil pan gasket is compromised there it will leak out. In your driveway this might not happen.

            Do as Rick suggested. Clean the engine, run it and figure out the location of the oil leak. I would personally call the mechanic that did the work. He should stand behind it.

            Comment


              #7
              Try getting oil absorbent pads and placing them under the engine. This will help determine the location of the oil leak after a short run.

              If its not concentrated it could be a bad ring as bounty suggests, this will let oil vapour by.

              It could also be no spark to one or more cylinders. This can cause excessive blowby symptoms on a new engine.

              Ann oil leak in any part of the pressurized system will cause dramatic oil loss in a short period!

              Chay

              Comment


                #8
                If the rear of the intake manifold is not sealed completely across the lifter valley and / or the valve covers are not sealed, you would be surprised how much oil the engine will puke at 3,000 rpm.

                Just one possibility.

                As mentioned, clean it, clean it and when you're finished, clean it.

                Then go for a ride with someone else driving while you look and feel for leaks. You will find it.
                " WET EVER "
                1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
                mmsi 338108404
                mmsi 338124956
                "I started with nothing and still have most of it left"

                Comment


                  #9
                  marine, my son has a 1994 5.0L Mustang that has a stoker kit producing lots of ponies. I don't know this as fact, but he tells me that this engine has a history of excessive crankcase pressure, especially when it's stroked. At 6,000 RPM plus, it will push the dip stick up slightly and puke oil onto the drivers side exhaust manifold. This past weekend we drilled another PCV opening in the valve cover and vented it to the atmosphere via grommet, valve and hose - no more crankcase pressure problems. Please understand, marine applications are not our expertise, so this may not be a viable solution. Maybe start with a compression test, as others have probably already suggested.
                  1999 Ciera 2655 5.7L BIII "Brenda Lou"
                  1996 Skeeter 1850DV 175 Mariner 9.9 Mariner. sold, sold, sold
                  1975 Lund 14' 25 HP Mercury. sold, sold, sold
                  2008 Dodge Ram 2500 4x4 6.7L Turbo diesel Quad Cab
                  Green Bay, WI on the Fox River
                  South Bay Marina

                  Comment


                    #10
                    Well fianlly discovered the problem. Cilynder #7 is reading 0 PSI. The rest were all good with 1-3 mreasuring 130 4 measuring 135 5 measuring 120 and 8 measuring 125. Now all I have to do is pull the motor undress and either repair or replace due to it being under warrenty

                    Comment


                      #11
                      marine wrote:
                      Well fianlly discovered the problem. Cilynder #7 is reading 0 PSI. The rest were all good with 1-3 mreasuring 130 4 measuring 135 5 measuring 120 and 8 measuring 125. Now all I have to do is pull the motor undress and either repair or replace due to it being under warrenty
                      you may not have to pull the engine, could be in the head, broken valve spring or bent valve, last week I bought a boat that had 20 psi in #3, it ended up being the rocker arm stud was loose and had backed out so the valve wasnt opening. pull the valve cover 1st, do a leakdown test

                      Comment


                        #12
                        Will do. I called the manufacturer and he suggested the same thing.

                        Comment


                          #13
                          Those compression test results would not indicate a new or healthy engine to me. I'd want to see at least 150 PSI on all cylinders.

                          Something is way wrong there. Maybe someone pulled a used car engine and gave it a fresh paintjob and sold it to you as a "rebuild", or something else was wrong with your timing or cooling system and in the short period the valves have been burnt out of the motor.

                          Comment

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