It's the crank sensor!
Join Date: Nov 2007
Location: Central Minnesota
I personally don't drain the block. As long as coolant is changed somewhat regularly, I don't think it's necessary.
And as for the radiator, I drain it by dropping the lower hose. Easier than getting to the radiator petcock and less chance of snapping it off/leaks.
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!