What is in my AC line at the expansion valve? Updated.

Well that's interesting. I look forward to the answer.

 

Jelly bean? Everybody throws out the black ones.

But, is it plastic, or does it feel like rubber?

 

Kinda looks like the boots they put on the threads for the dryer, but they are rubber/silicone.

 

I was thinking in line with @062. I'd be easily trying to nudge it out with a pick, or blow it out with air from the other end

 

Looks like someone forgot to remove a plastic plug when they installed a line or other part. I saw that happen with an oil supply line for a CAT turbo on a fresh in frame, didn't work out well for that turbo in about 30 seconds.

 

Saw similiar with a 60 Series injector. Made a service call to USA Truck cause they couldn't seat an injector. I asked them over the phone if the protective cover was still on the new injector.

In their defense, the protective cover was no longer on the new injector, it was stuck in the cup.

 

I agree and did leave a plastic cap in a turbo outlet once myself. New injectors turbo etc. It was on a 4070B. Started it up and about the time air was getting worked out of the fuel it went boom. While trying to figure out what just happened and or get up in the jacked up cab to shut it off the second boom happened. It was hung out in the muffler and came bouncing around on the floor covered with suet.
Just dig that thing out, throw in away and flush everything out.