I have the same problem in my '95 straight 6. Mine is the sending unit. That could be it.
The transmission cooler (possibly part of the radiator) has failed.
The water pump does not have a specified life span. The time to replace it is when it is leaking or noisy.
Probably a blown or leaking head gasket.
check your radiator hoses and change gaskets
If losing anti freeze but not visible leaking typically means bad head gasket. Antifreeze is leaking into combustion cylinder and therefore evaporating and going out exhaust pipe as steam.
That is most likely antifreeze. Have the cooling system checked for a leak.
If it is motor oil in the anti freeze, then it is either a cracked head, cracked engine block, or a head gasket blown. If it is transmission fluid in your antifreeze, then the radiator is leaking from the transmission cooler ----- although usually that would cause antifreeze to be in your transmission fluid.
You have a leaking transmission cooler, usually part of the radiator. The transmission fluid is mixing with the antifreeze turning it pink.
Transmission coolant hoses (in and out) are leaking. The Y-manifold is below the filler cap on bulk head. Hoses connect from here straight down to transmission.
Antifreeze is typically green, but the newer stuff is "gold". If you're getting red liquid leaking from the radiator it's probably the transmission coolant line.
There is no antifreeze in a refrigerator.
Look at the oil on the dipstick. If you have antifreeze leaking into the crankcase the oil will be milky.