finally got around to looking at this thread. Seems like my cap is difficult to install and remove, and I think it has internal threads (not sure) but I have wondered if it could fail some day since it is a 2006...Just ordered a replacement off Ebay. Right now it is a blistering -11 degrees out so it may not get replaced for a bit, the original one is still working but it would be just my luck that it would fail if I didn't have a replacement on hand.

Thanks for bringing this to my attention. should be here in a few days...

 

Get a pair of stainless steel worm gear clamps for the install

 

I second this

 

Checked my OE one today, it is good at this time.

 

my filler neck died a few years ago, a metal replacement was purchased through a Chinese site, alive and well to this day.
I didn’t buy new clamps; I used old clamps with a spring compression principle.

 

Next time I do the Dexcool change, should get a metal replacement.. Good info.

 

Yup, that code. I already knew of the thermostat and I did get a genuine ACDelco.