Thanks. I wasn't thinking at all to replace the hose with a larger diameter. If anything, I would possibly only be looking at drilling the inside diameter of the reservoir inlet to be slightly larger just to minimize chances of it getting clogged with rust again. I have a background in mechanical engineering. I would guess it was like an 1/8 of an inch in diameter max, if not smaller. But yeah, My first van. I bought it 2 years ago and I did see that some work/maintenance was to be needed and did not think to check much since I bought it, since it was running like a champ as of a few weeks ago. The cooling system was badly neglected. Leaves me wondering where the rust usually comes from, the upper engine coolant cavities since the coolant level was always low the past 2 years? Also, I've read elsewhere the coolant level in the radiator when cold should be visible and 1/2" to an inch below the radiator cap.On your coil pack, switch 4 &
Welcome to the forum.
No, replacing radiator will not help if the problem is the thermostat. First culprit will always be the thermostat, then radiator fans and lastly the radiator.
That little hose between radiator and overflow bottle is the correct size for the application, any larger and it might not work.
It will never clog in a well maintained engine, shouldn't be any rust ay all.
Seems like your cooling system was badly neglected.