Auto body repair & detailing: crack repair, swipe, cracks

Question
I'm working on an old pickup and I've already got it primered.There are some cracks coming through from some old body work.Is it allright to fill those and primer over them?

Answer
BOB.....I WOULD SAND THE CRACKS UNTIL SMOOTH AND THEN APPLY THE FILLER. IF YOU SWIPE FILLER OVER THE CRACKS THEY WILL COME BACK AFTER YOU ARE DONE.

THE REASON IT IS CRACKING IS BECAUSE THERE IS TO MUCH FILLER IN PLACE AND THE METAL WAS NEVER WORKED OUT FAR ENOUGH.OR IT COULD BE THAT MOISTURE GOT INTO REPAIR AND HAS BEEN LIFTING.

GOOD LUCK