Can be the battery has a dead cell which will require the battery be replaced. Can also be anything on the vehicle that is on pulling from the battery. Any light that is on or any relay that is stuck will drain the battery. Check under hood light, trunk light, glovebox light, interior lights, etc.
Where is the oil dran plug on cadillac deville, 1999
Bottom of the radiator.
The 1996 Deville drain plug is in the bottom of the radiator close to the bottom hose. It is in a very hard place to reach.
Disconnect the lower hose
Bad battery or a parasitic drain
Where is the Drain Plug for the Radiator for a 1993 De-ville?
There are a few reasons why a battery may drain overnight on a 1987 Cadillac Fleetwood. One reason could be the alternator needs replaced.
Either the battery has a dead cell and needs replacing or something is pulling power from the battery when the engine is off. I had a problem with my 1986 Cadillac DeVille where the power antenna was stuck and the motor would run all night trying to lower the antenna. To resolve the problem I just removed the fuse for the power antenna motor.
Underneath the A/C evaporator core case which is in the engine compartment
If you cannot find the drain plug you can also pull the lower radiator hose. MAKE SURE THE ENGINE IS COLD!!!
Happened to my 97. The alternator went out. Had to replace it and get a new battery. No problems since.
A raidator in need of a flush will not cause a battery drain.