O6 freightliner fuel cap leaking

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Jd9760, Dec 22, 2023.

  1. Jd9760

    Jd9760 Bobtail Member

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    Dec 22, 2023
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    06 freightliner fuel cap leaking help
    So I have changed the gasket, sealing surface is smooth.
    Why does this thing still leak.
    It seems to be coming out this plug on the top.
    I'm assuming its some kind of vent but why is it needed if the tank is already vented off the top with vent lines to leak on to the ground.
    Leaks worse the more fuel is in it.
    Since the tank is vented can I weld this round plug on the cap shut?
     
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  3. JB7

    JB7 Medium Load Member

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    Here's a good thread. See post #11.
    Fuel Caps leak! | Page 2 | TruckersReport.com Trucking Forum | #1 CDL Truck Driver Message Board (thetruckersreport.com)
    Also this.
    How to Stop Fuel Cap Leaks on Heavy Duty Trucks - Heavy Truck Solutions
    Good idea to check the vents coming off the top of the tank. Blow through the vent and hose.
     
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  4. SmallPackage

    SmallPackage Road Train Member

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    If you have the type were a freeze plug wont work then a simple dab of JB weld will work. Frieghtliner had two piece screw on caps back before the ones you have came out that would leak were the 4 rivets fastened the dome top on. JB also solves that.
     
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  5. Ridgeline

    Ridgeline Road Train Member

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    I have seen idiot drivers who filled the tanks up so much that it just was ready to spill out, not the 85% capacity that it should be, so my question is - how full is the tank when it leaks?
     
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  6. Jd9760

    Jd9760 Bobtail Member

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    Dec 22, 2023
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    It will leak with a half tank. I think it's splashing up
     
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