Check out this link. It has all the info you need http://www.freeengineinfo.com/cadillac-northstar-starter-replacement.htm
Find where the fluid is coming out and repair/replace it.
A bad radiator is a radiator that is leaking or clogged. If you are loosing coolant then you have a leak that should be easy to find if the leak is at the radiator. If it is clogged your engine will overheat.
If your radiator is leaking then you will need to replace it. Additionally, if you find that your car is constantly running hot you will need a new radiator.
Call Around; Find A Radiator Shop or A Mechanic That Can Pressure Test Your Radiator. This Should Help
The only way to find out is to have a look it could be anything.
the cooling fan relays are behind and below the center of the radiator
If you cannot find the drain plug you can also pull the lower radiator hose. MAKE SURE THE ENGINE IS COLD!!!
It could be water pump, leaky radiator, hoses, head gasket, or just about anywhere else that the coolant circulates. You'll need to get under and find out where it's leaking.
If your coolant is leaking, chances you have the head bolts pulling, a common problem on northstar engines. Dealer head bolt inserts don't work, they will tell you that, and no guarantee. The only 100% success rate fix would be " NS300L ". These are longer head bolts and inserts. You can find them on the web, and on Ebay.
First, you must find out WHERE it's leaking. If it's a radiator hose or heater hose, replace the hose. If it's a water pump leak, replace the water pump. If it's a leaking radiator, take it to a radiator shop and have the radiator replaced or repaired. If it's a freeze plug, head gasket or other leak, you'll need more serious repairs.
easiest way is to fill radiator and look and see where fluid is coming out, but Im sure you thought of that. The best way is to plug the ends of the radiator up with some type of rubber stopper then insert blow air through the drainport while holding it under water. Wherever the bubbles are coming from is where its leaking.