So title explains the issue, I started noticing about a month ago that my coolant level in the reservoir was very low. I filled it up, drove around and checked it again a few days later (after driving several more times in between). Saw coolant on the hose by the clamp and around the cap. I replaced the clamp on the hose line thinking it was coming from there as that was where most of the coolant was. Drove some more and checked it to find that it's still leaking even with the hose on there with a fresh clamp. I am assuming at this point its probably coming from the cap as there was also coolant around the cap. I figured the cap was good because it's on their tight. Pulled the cap off, didnt see any cracks or anything. I was however surprised there was no rubber seal or anything on there.

Guess wondering if anyone has had a similar problem and if just replacing the cap would solve this. Again the cap looks perfectly fine but I am guessing with age maybe its just expanded a tiny bit or something and is whats causing the leak. Also does it need to have some sort of rubber ring seal in it or is it fine as is without?

 

I have a 2017 SL and I have had this problem since the car was about a week old, new. I went through the same analysis you've been through when I first noticed the antifreeze residue on the container, it appeared that it was coming from the cap. I never could detect when the league started but I noticed that every time my car had been idling for any extended period of time and really hot weather, the residue would appear. I just could not find the reason for the coolant kind of blowing around the threads on the container and cap. Out of desperation I rummaged through my stash at various types of seals and gaskets and found a rubber o-ring that just fit underneath the cap. That has prevented this from reoccurring. Thinking back, I owned an '07 Altima SL before I own the new Maxima and it had the same problem. I took the Altima to the dealer and they could not come up with a reason for the problem, even after replacing The thermostat. I wrote that off to some kind of design defect and lived with it.

 

Gottcha, I will go ahead and look for a o-ring and see if that resolves the issue. That was kinda my first thought when I figured it was the cap and was very shocked there wasn't one in there already! Thank you for your reply!