It was from the bleeder funnel adapter and I’m afraid it’s going to cause more problems than I’m already having (which are horrible!!). I read elsewhere that someone dropped a rubber tip into their radiator and replies said it won’t get through anywhere. Will it melt and get through or gunk stuff up. I sucked as much as I could out of reservoir and do not see it at all. It’s not laying around anywhere though. 😫

 

it wont harm anything it wont melt it wont get hot enough to melt rubber.

 

If the O-ring was rubber, it should be okay unless it starts breaking down over time. If you're worried, you might want to drain the reservoir and check for it. If you replace it, look for one made of hnbr since it's more resistant to heat and fluids. I've seen regular rubber O-rings swell up or break apart in coolant systems, which can lead to clogs or leaks.