I took her on a cruise on the freeway (was taking her to a 2nd gen specialist) and she was doing great but she stalled about 20 minutes in, (65 MPH) it reeked of coolant. The coolant was topped off, so it wasn’t lacking coolant. The back of the block (where the air intake/air cleaner is) was smoking very lightly. The oil was good, the transmission oil was good. 10 minutes later, she starts, with no hesitation, and runs. The fuel gauge was acting erratically. Going from full, to empty, and the light came on. She had 3/4 tank in. Has anybody else had a similar issue? (5.9 360 V8 2500) Thank you!

 

Might not be full of coolant. Remove your radiator cap and check to ensure that the radiator is full of coolant. Since you smelled coolant, you might have a coolant leak somewhere (cracked/leaky radiator, leaky heater core, freeze plug rusted/leaking, etc.). You can also pressure test the cooling system to try to see if you have a leak that you can't readily see.

 

The heater core is definitely bad, we tested it, and no heat at all. I can’t say if I have enough coolant as I poured it in the reservoir tank instead of the radiator. (Long day) I figured it wouldn’t hurt since I topped off the radiator in December with 2 gallons of antifreeze. The reservoir tank was almost empty.