No , it's best to add coolant when the engine is cold
( NO ) with the engine cool
Your engine should be cold ( to be on the safe side) when adding antifreeze/coolant. i let the car sit overnight and then add it.
Yes
=To properly flush the antifreeze on a 2002 Yukon you will need a antifreeze vacume system you will need to start the car and have it running turn on all the heating modules to high and have the car reved at about 1.5 r.p.m, or a little higher to activate the vaccume this will start sucking the old antifreeze out. When the radiator is empty{you will know when it is empty because there will be no more antifreeze coming out}you can then fill it up with half and half antifreeze[half water half antifreeze].=
why does car need topping up with water and antifreeze each week? why does car need topping up with water and antifreeze each week?
It will overheat, unless you can successfully air cool it.
I need to fill my car's radiator with antifreeze before winter comes.
No
You need to have your antifreeze up to par and if it is a leak you are worried about until you get somewhere to have it fixed there are quick fix solutions such as Barr's Leak that you can use it will seal the leak temporarily to get you to where you are going. Do not ever open your radiator cap if your car has been running - only open it when it is cold.
increases, and lowers
i believe your heater core has died
If it is a four cylinder car, it will need between four and five quarts of oil. It is recommended to put four quarts of oil in the car and then check the oil level before adding more.