My new grandson is only 2 weeks old. He is constipated. Years ago we would just take the babies temp rectally to loosen things up. Do they still do this or is there another way to help flow things along?

What you could actually do is to give the baby more water. Or bring him to his pediatrician to check why he's being constipated. It may be that the milk (if he's taking formula instead of breastfeeding) is not for him and should be changed.