So my 98 Chevy K1500 is drinking about a gallon of antifreeze over two days. All the hoses are good, heater core not leaking, weep hole is dry on the water pump, no white smoke in the exhaust, no anti freeze in the oil, and radiator is new. 2-3 days ago it started running rough at idle and anything above 2500 rpm's to about 4000 runs like it is not getting enough fuel.

I love this truck, it has served me very well. i have put thousand of miles on this truck. I have 241300 miles on it... it's a sad day...

 

I'd suggest pull a couple spark plugs, if they look normal, with what you are posting, i'd next suspect the overflow tank leaking

 

Could need a head gasket with one of the water jackets leaking into one or more of the cylinders.

 

Like the guys above me said check those areas first. After that check the metal lines going into the radiator, could be a leak at the top line or bottom. Thats what happened yo mine, ended up needing a waher at the bottom line that was missing.

 

Intake gaskets?