I have water on the floor of the drivers side. Is it the heater core on my 1994 Cadillac eldorado

Your heater core is leaking, bypass the core by removing hoses from firewall and joining together, or cable tying over, this will get you back on the road until you can replace the heater core.

Not sure if this will help but this is on a 2001 Eldo which should be close to what you have. I would also suggest the library and check out a Chilton's repair manual for you car.
Heater Core Replacement 2001 Eldorado Archive Cadillac forums Cadillac...

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antifreeze anywhere inside the cabin is a sign of a leaking heater core. Rub the liquid between two fingers. If it feels oily, it's coolant.

This actually sounds like your motor is not the problem it sounds as
thougth your transmission is in need of work. if you have flushed your
system also may look at your oil pump system as the change in pitch of the road to climb hills may infact be pulling sludge against the sump
tube screen and plugging the oil pump. these are the only two reasons I can see for this to happen if system only dose this when climbing a hill
.

Heater core replacement instructions

It could have for sure but it will come back sometime in the future. It would be wise to start planning for its replacement now. Hope this helps.

your heater core needs to be replaced

The heater core may be stopped up.Remove bothe heater hoses from the heater core,and use a water hose to flush out the heater core.Put the water hose up against one heater core pipe,it will come out the other pipe.Make sure the vent door inside the car is moving when you select heat,If I can help,any further,please let me know.>>[email protected]

Engine coolant will feel oily and the windshield will fog up and the car will stink. If it is just water it could be coming from the passenger door weatherstrip at top. The ac drain tube , if stopped up will also leak water in the floorboard.

This sounds like the heater core radiator has a leak. After disconnnecting the negative battery terminal and draining the coolant, you will have to perform the following:
1) disconnect the heater core hoses.
2) remover right side sound insulator and glove box module.
3) Remove the programmer shield, if equipped and disconect the air mix valve link.
4) Detach the programmer vacuum and electrical connectors.
5) Remove the heater core cover, leaving the programmer attached.
6) Remove the heater core retaining screws and the heater core.
7) Take the heater core to a radiator shop for repair and re-install.