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  1. #1
    Join Date
    Sep 2017
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    Carrying Place, ON, Canada
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    5

    Question New here and just figuring things out.

    My mercruiser MCM 190/488 has a leaking engine oil cooler. It is leaking coolant out into the bilge. For some reason my Seloc manual has nothing in it about this cooler. Might there be any forums or write ups on this repair.

    Thanks,
    Jamie.

  2. #2
    Join Date
    Jun 2006
    Location
    Spotswood, NJ, USA
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    3,861

    Default Re: New here and just figuring things out.

    thats because its a SELOC. The heat exchanger is either 3 or 4 inch .there are 2 drain plugs in the aft end. rearmost is raw water, forward is the A/F side.

  3. #3
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    Sep 2017
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    Carrying Place, ON, Canada
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    Default Re: New here and just figuring things out.

    Sorry, it is not the heat exchanger that has a problem. It is the oil cooler that is located below the intake manifold and above the oil filter that leaks coolant.

    Jamie

  4. #4
    Join Date
    Sep 2008
    Location
    Maryland - USA
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    6,826

    Default Re: New here and just figuring things out.

    The only "oil cooler" that should be there is the power steering fluid cooler.....and that doesn't have "coolant" in it, only raw water and the PS Fluid...

    If the PS cooler is leaking, and its original, probably best to replace it....less desirable option would be to remove it and take it to a radiator shop for testing/repair.

  5. #5
    Join Date
    Dec 2015
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    maplevalley WA
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    Default Re: New here and just figuring things out.

    Just replace it if it is leaking. Do not take a chance on repairing it they are a preventive maintenance item and should be replaced at regular intervals.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  6. #6
    Join Date
    Jun 2006
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    Spotswood, NJ, USA
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    Default Re: New here and just figuring things out.

    Quote Originally Posted by makomark View Post
    The only "oil cooler" that should be there is the power steering fluid cooler.....and that doesn't have "coolant" in it, only raw water and the PS Fluid...

    If the PS cooler is leaking, and its original, probably best to replace it....less desirable option would be to remove it and take it to a radiator shop for testing/repair.
    Find regular A/F leaking from there means the heat exchanger is leaking A/F into the raw water side of the cooling system

  7. #7
    Join Date
    Jun 2006
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    Spotswood, NJ, USA
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    Default Re: New here and just figuring things out.

    found your oil cooler, its on page 7A-6 of manual 8 the site I use for pics is down ,
    You may have to use a regular transmission cooler (not a power steering cooler) for the engine oil and remove your item and screw the oil filter direct to the block
    Last edited by Bt Doctur; 09-07-2017 at 12:26 PM.

  8. #8
    Join Date
    Sep 2017
    Location
    Carrying Place, ON, Canada
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    5

    Default Re: New here and just figuring things out.

    Thank you. The leak is around the plate that secures the bottom of the cooler to the intake manifold. I was told there is a long O-ring that is problematic. Of course this part is no longer available they told me. Either have a long O-ring made or use high temp gasket maker, apparently. Just was hoping someone had tackled this job and had advice.
    will try your suggestion with the manual. Does one have to pay to see it?
    Jamie

  9. #9
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    Jun 2006
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    Spotswood, NJ, USA
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    Default Re: New here and just figuring things out.



    Never had to change one but it might be the same one used on Ford oil filters.The same part number for the oil filter gasket and the housing.
    Last edited by Bt Doctur; 09-07-2017 at 05:44 PM.

  10. #10
    Join Date
    Jun 2006
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    Spotswood, NJ, USA
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  11. #11
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    Default Re: New here and just figuring things out.

    unless you mean #11

  12. #12
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    Default Re: New here and just figuring things out.

    To do it correctly remove the plate and clean the surfaces.Apply a consistant narrow bead in the cover about 3/16 above the edge of the cover and walk away untill the next day. LET IT CURE
    Install and tighten cover

  13. #13
    Join Date
    Sep 2017
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    Carrying Place, ON, Canada
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    Default Re: New here and just figuring things out.

    Hi Bt Doctur
    The diagram looks exactly like the one in question. Will take it apart with a bit more confidence now.
    Sure glad the coolant leaked out into the bilge rather than into the engine oil.
    It would seem there are O-rings where the oil passes through the plate. Will find out I guess.
    Will follow your instructions

    And thanks for taking the trouble to figure this thing out.

    I have heard that these 488 model engines were less than successful. It seems the Al block had no sleeves in the cylinder bores. The local marine guy told me to keep the revs below 4000 rpm and we won't have any trouble. ??
    Hope he is right.

    Big thanks,
    Jamie

  14. #14
    Join Date
    Sep 2017
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    Carrying Place, ON, Canada
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    Default Re: New here and just figuring things out.

    Yes, the "no longer available" is number 11 in the diagram

  15. #15
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    Default Re: New here and just figuring things out.


  16. #16
    Join Date
    Dec 2015
    Location
    maplevalley WA
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    Default Re: New here and just figuring things out.

    You can always get bulk o-ring material and just use superglue to join the ends. Just make sure it is the nitrile material. That just looks like a manifold cooler to me. Go to boatinfo library and find your engine.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  17. #17
    Join Date
    Dec 2015
    Location
    maplevalley WA
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    3,549

    Default Re: New here and just figuring things out.

    Looking at the flow chart it is warm coolant flowing through the intake jacket to preheat the fuel going into the cylinders.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  18. #18
    Join Date
    Nov 2011
    Location
    tennessee
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    2,622

    Default Re: New here and just figuring things out.

    I have heard that these 488 model engines were less than successful. It seems the Al block had no sleeves in the cylinder bores.
    Yes they have sleeves and sold several to dirt track racers...balanced,flowed,custom cam,sheet metal intake,1050cfm holley,8500rpm= lite weight powerhouse of 500+HP!!!!!
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

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