Those caps suck. The rubber is cheap and barely lasts a year. I have one on plugging a coolant port on a non land cruiser - I have a 4 pack of spares in the glovebox
Those look decent. I had tried a silicone one at some point and I noticed it inflated a bit, like a balloon, when hot. Maybe that’s how it works but it wasn’t confidence inspiring. It didn’t have the reinforced look of the type you linked though. It was just thick silicone.
Mine is on the rad of a 70’s C10. I check on it every time I check the oil.
I will be tackling the dreaded "Temperature Slider Stuck/Stubborn" Issue over the next week as I am scheduled to take my truck into an Air Conditioning specialist in two weeks.
I will post some pics and videos of what is happening, and then most likely will be pulling off the dashboard to chase the wire that is getting stuck somewhere.
