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Glycol Tank Cap Will Not Tighten

The cap on the Alde glycol tank in my 2019 320S is always loose.  During trailing glycol splashes up to the cap and leaks out causing an unwanted mess with glycol always running down into the area under the rear.

I have used tape on the threads to try and get the cap to stay tight but that is not a very long term or 100%  fix.  

I would buy a new tank if I could be sure the cap would fit tight and seal. 

Do some owners of 320S' with the tank in the rear have tanks that the cap fits tight and seals?

Anyone buy a new tank and found the new tank cap seals?
2019 T@B 320S

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    berggerbergger Moderator Posts: 1,031
    I'm pretty sure the consensus is that the caps generally do not snug down tight as it is not a pressurized system.  The cap on our 400 will screw on a bit but if I turn it a little too far it will go loose.  It is kind of finicky.  But even being a loose fit we've never had glycol leak out of it.  How much glycol is in you expansion tank?  Maybe it's over filled a little?  Or it could just be the size and location of the tank.  I think the 400 uses a larger tank and ours is in the very front of the trailer not the rear where I believe yours is located.  Curious to see if anyone does have a tank with a tight cap.  
    2021 T@b 400 BD  "Vixen Gail" 
    2018 Nissan Titan Pro 4X "Big Bird"
    Leadville Colorado
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    manyman297manyman297 Member Posts: 1,218
    Ditto what @bergger said for us. It has never tightened. I just snug it down.
    2021 400 BD
    2020 Tacoma TRD Off-Road 
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    grassgdgrassgd Member Posts: 134
    bergger said:
    I'm pretty sure the consensus is that the caps generally do not snug down tight as it is not a pressurized system.  The cap on our 400 will screw on a bit but if I turn it a little too far it will go loose.  It is kind of finicky.  But even being a loose fit we've never had glycol leak out of it.  How much glycol is in you expansion tank?  Maybe it's over filled a little?  Or it could just be the size and location of the tank.  I think the 400 uses a larger tank and ours is in the very front of the trailer not the rear where I believe yours is located.  Curious to see if anyone does have a tank with a tight cap.  
    My glycol level is not overfilled, and the tank only holds about 1/3 gallon at max fill level which is about 1/2 filled so as the trailer bounces on the highway it easily splashes on the loose cap.  It doesn't take much glycol to make a mess.

    Even though the Alde system is not a closed system (it is vented to the atmosphere) it would be much better if continuous exposure to oxygen is eliminated.  That would increase the glycol life.  I am working to have the glycol tank vent to an expansion type of device and eliminate the vent to atmosphere.  Hence, I have two reasons to have the cap seal - stop the mess and close the system to constant oxygen exposure.
    2019 T@B 320S
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    dragonsdoflydragonsdofly Member Posts: 1,927
    @grassgd-have a 2017 320S. 45,000 miles with reservoir in the back. We just snug the cap a little and have never had the cap leak. Hundreds of miles on gravel and first nation roads in some remote locations and no leaks. I wonder why the difference?
    2017 t@b sofitel(Dr@gonsFly)TV 2015 Silverado 2500hd(Behemoth). Wyandotte, Michigan.
    Draco dormiens numquam titilandus.
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    Maxcamp8Maxcamp8 Member Posts: 225
    Check the cap and tank for malformed threads if possible.  Common in plastic gas cans and other injection molded items.  Measure OD and see if you can transfer a cap from another object- gas can or water tank.  I've swapped out caps on gas cans all too often.

    2021 T@B 320S Boondock/ 2012 Tacoma 4 cylinder truck / 2023 Tacoma 6 cyl. truck

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    grassgdgrassgd Member Posts: 134
    Maxcamp8 said:
    Check the cap and tank for malformed threads if possible.  Common in plastic gas cans and other injection molded items.  Measure OD and see if you can transfer a cap from another object- gas can or water tank.  I've swapped out caps on gas cans all too often.
    The threads on the cap look fine.  The threads on the tank are not continuous (ie gaps without threads so I think it's not the cap that's the problem but I'll check again.

    When I get the trailer out of storage again, I plan on measuring the tank opening to see if I can fit an End of Pipe Gripper or a Clean Out Plug Gripper or similar:


    2019 T@B 320S
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