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  1. #1
    Chief Petty Officer kwoolard's Avatar
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    Default Oil Pan Plug Size? - 1999 5.7 GM

    I am going to get one of those quick oil drain hose kits and was wondering what size my drain plug is.....1/2-20, 12mm or 14mm?

  2. #2

    Default Re: Oil Pan Plug Size? - 1999 5.7 GM

    Your 1999 5.7L oil pan is metric......

  3. #3
    Supreme Mariner
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    Default Re: Oil Pan Plug Size? - 1999 5.7 GM

    why not just suck it out of the dipstick like 99% of marine engines are designed to do ?
    most,not all, late model GM pans are 14MM, that being said the only way to know for sure is to remove yours and measure the thread diameter and pitch.

  4. #4
    Chief Petty Officer kwoolard's Avatar
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    Default Re: Oil Pan Plug Size? - 1999 5.7 GM

    I have been using the dipstick method but I just don't like the fact that I can't get all of the old oil out. It doesn't matter now anyway, I was thinking I may have enough room around the engine to get down there and install one, but found out I don't have as much room as I thought. I guess I will just stick with the dipstick method....

  5. #5
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Oil Pan Plug Size? - 1999 5.7 GM

    I have been using the dipstick method but I just don't like the fact that I can't get all of the old oil out.
    I don't know what you have there, Mercruiser or Volvo, but both of those have the dipstick attached to the bottom of the pan, so you will be getting as much oil out with the dipstick as if you pulled the plug on the bottom of the pan. Besides, those hoses that go out the drainplug hole are worthless. They are slow, even with warm oil, and will take a day to drain.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
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