15 Sierra 6.0 Sulfur Smell

[15DenaliSummit]

Hey guys new member here, I just bought a certified used 15 Sierra 2500hd Denali 6.0 at 67k miles, I’m getting a sulfur smell on high idle and highway driving at low load, also sometimes when I fill up. Its definitely coming from the engine bay. I was wondering if anyone has any advice? The truck is at the dealer right now and they told me they couldn’t replicate the smell like they always say. It’s also has an aftermarket second battery kit to it, that may be useful info. Thanks in advance and I wish everyone a happy holiday. 

[Ropegun2k]

Sulfur eliminates quite a few possibilities.

I would be willing to bet it’s coming from the battery. Is it hot, swelling, or leaking acid?

Seen this happen a few times in various vehicles. I replace both the alternator and battery at the same time when it happens.


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[15DenaliSummit]

I got my truck back last night, the previous owner had a second battery put in but it wasn’t wired anywhere near right. The positive wire for it was melting and that battery was boiling. The dealership just removed the positive cable from the battery and it stopped. Thanks for the advice