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Thread: Diesel Tank-easy sludge check

  1. #1
    Join Date
    Dec 2008
    Great South Bay, Long Island, NY USA

    Default Diesel Tank-easy sludge check

    When I had to remove and repair my leaking diesel fuel tank this summer, I also found I had a quite bit of sludge in it that probably would have caused us a problem in the future as we expand our cruising range next season.

    I was actually somewhat surprised because I frequently check the Racor filter, and it never really looked bad enough to suggest I might have a sludge problem. Point of reference--the tank is 15 seasons old.

    As you can see in the attached picture, my tank has an inspection plate on top; it looks like it is easier to get at than it really is. When I had my tank repaired and flushed, the radiator shop that flushed it took that plate off but left it for me to replace, as the original neoprene gasket became deformed as he pulled it from the tank and plate; he also did not have any neoprene material to use for a gasket. My marina had some for purchase, so it was easy to buy.

    My guess is that if your tank is similar, you will have to replace the gasket, as well. Cork might be easier to work with, but neoprene was what was on the tank, so that is what I used. (You could probably coat the area with Permatex, as well, which would make it very easy to replace.) It is not really difficult, but it is time consuming to cut the neoprene to a properly fitted gasket with the necessary holes to screw through the plate into the tank. Fortunately, the tank was out of the boat and in my garage which made it a little easier to do.

    I don't think I would really want to remove and replace my inspection plate with the tank in place if I don't have to. I would have had to remove all the fuel lines anyway to be able to lift the inspection plate off the tank.

    So how do you check for sludge without removing the inspection plate?

    While I was disconnecting the fuel feed and return hoses to remove the diesel tank, I realized that there was a quite a bit of sludge in the fitting for the feed hose barb. Looking back, and having the advantage of seeing the pickup tube out of the tank, the pickup tube diameter is wider than the opening in the fitting at the top of the tank (with the red shutoff valve). Thus, I believe, the sludge got caught in the smaller opening as it was drawn out of the tank into the fuel feed line. It was probably a matter of time before it got clogged and caused me problems.

    My suggestion is if you don't have an inspection plate on your tank, or if it isn't easy to get at, try unthreading the fuel feed line barb from the tank fitting. If you don't have any sludge, you are good to go. If you do, you might want to look into it further before you do have any problems.

    Last edited by searenitysail; 11th April 2011 at 06:38 PM.
    "People sail for fun and no one has yet convinced me that it's more fun to go slow than it is to go fast." -- Dick Newick

  2. #2
    Join Date
    Sep 2017
    Boat: Croatia; Living in Tokyo during the months not on the boat

    Default Re: Diesel Tank-easy sludge check

    Thanks for this advice!

    Would it be possible to see sludge using a technical endoscope resisting diesel and in from the re-fill opening?

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