Can I use some silicone grease between the cap and the neck to help seal it? I don’t believe that four different caps are all faulty in a row, each one being a different brand.
That will just make a mess.
If you know that the radiator is stock or a Mopar unit it could be that you are being given the wrong radiator cap. The only way the cap would leak as you describe is if there was a great amount of volume of coolant or air leaving the radiator. I would imagine it would take a couple cylinders to make it do that and you would know there was another problem.
what gets my attention is that you say you have driven the van for some time after the initial “puke” and the level does not change. That is basically the way old cooling systems worked. You did not fill the radiator full when cold.
You said you checked the hose to the overflow tank,,,did you check the overflow tanks vent? If that is plugged that could cause your symptoms.
Well there you have it: View attachment 72367
I really did not think I’d find anything out of the ordinary with the reservoir, but after a good ten minutes of pulling and straining I got the overflow hose off only to see this.
I couldn’t even poke a paper clip through that gunk, it’s an absolute miracle I had coolant bursting out of the cap instead of a blown hose on the highway. Another trip to the junkyard is in order it seems.
I suspect that before the previous owner replaced the water pump, they used some stop leak to try and remedy a leak in that area, thereby causing this tough gelatinous buildup. At least I learned that lesson the easy way, to not to use stop leak in any of my vehicles.
Thank you all so, so much for the help. I genuinely would not have ever found this out on my own and it’s why I keep coming back to the forum. Much appreciated everyone.