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Def fluid leaking

13171 Views 16 Replies 11 Participants Last post by  tbendiesel76
My DEF fluid is leaking down or running down the side of my truck by the full cap. Has anybody else had this problem? The cap is put on tight.
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I have noticed mine leaking, just under the fuel door. Just notice a bunch of dried def under there. But I did just get it back from the dealership where they did an oil change and filled my def tank so some spillage may have occurred.
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I have noticed mine leaking, just under the fuel door. Just notice a bunch of dried def under there. But I did just get it back from the dealership where they did an oil change and filled my def tank so some spillage may have occurred.
Mine just got refilled also but I have found dried fluid a couple times. Also found it when it was new from dealer. Maybe they are filing it to full but it seems like like it is going three fluid to fast.
I also had the same issue. I found the rubber surround for the fuel filler neck and DEF filler neck was up around the threads of the DEF fluid filler neck, this prevented the DEF cap from being installed completely and sealing, despite clicking as if it was tight.
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Hello Jerry V,

We apologize for the unexpected leaking concern with your truck. If you would like for us to look into this further, and reach out to the dealership, let us know in a private message. Please be sure to include your VIN, current mileage, contact information and preferred dealership. Thank you.


Kindly,

Anthony J.
GM Customer Care
I also had the same issue. I found the rubber surround for the fuel filler neck and DEF filler neck was up around the threads of the DEF fluid filler neck, this prevented the DEF cap from being installed completely and sealing, despite clicking as if it was tight.
I have noticed mine leaking, just under the fuel door. Just notice a bunch of dried def under there. But I did just get it back from the dealership where they did an oil change and filled my def tank so some spillage may have occurred.
So how was it corrected..by the dealer or could you do it?
So how was it corrected?
So how was it corrected..by the dealer or could you do it?

I believe mine was dealer spillage, was clean when I filled up yesterday.
I believe mine was dealer spillage, was clean when I filled up yesterday.
I am fairly confident that some dried DEF crud broke loose and prevented the seal from seating properly which led to the leak. I took the cap off and brush it off a bit and no more leaking.
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Seems to be a recurring problem. Our brand new 2018 just went back for this. Another reason i hate emissions equipment
I have never had a leak, but I am the only one who has added DEF to my truck. I do have the crusty stuff, will pay more attention to any build up and wipe it down better than I have. This stuff is corrosive from what I have heard, so wipe your truck down where it spilled.
Resurrecting this thread as I've noticed the same issue with my truck. Streaks of DEF condensate running out the fill cap and down the side of my truck. It's quite noticeable and pretty annoying. I've tried soaking the DEF cap to clean it, but that doesn't seem to stop the issue.

2018 Z71 crew cab - 41k miles
My DEF fluid is leaking down or running down the side of my truck by the full cap. Has anybody else had this problem? The cap is put on tight.
I had this same issue right after I bought my Colorado a few months ago, initially thought salesman spilled some when he filled it up. It kept appearing and spilling so I went back to the dealer and showed them. They looked at me and said “that’s weird” Dropped it off for them to look at it, turns out there’s a technical service bulletin out on it, GM knows about it, it’s an easy fix. It’s been a while but I think there was a problem with the way some were mounted/sealed.
Go to your dealers service department and show them and ask them to check for service bulletins on it.
My DEF fluid is leaking down or running down the side of my truck by the full cap. Has anybody else had this problem? The cap is put on tight.
mine leaks terrible as well. Brand new Colorado and I have horrible DEF leakage. Is there a fix?
I had this issue when new. The tech bulletin I got from the dealer shows the rubber boot around the filler creeping up the filler neck so when you put the def cap back on it catches the boot and doesn't seal properly. It just says to push it down with your fingers. Hasn't happened since. Probably just an issue from them installing it at the factory pushing the boot all the way out.
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