I have a 1999 mercury sable and when I fill the resivore the water runs into the oil pan.

place large masonry mixing tray[home depot]under transmission pan to catch fluid. remove 19 bolts on transmission pan.pull off filter.make sure o-ring gasket is removed if it is not on old filter.push in new filter.clean old gasket off pan.install new gasket and pan. refill transmission fluid.check pan for leaks.

are the cooling fans running? is it loosing water from exhaust or in the oil check these things water is going somewhere

ok there are 2 ways..

1 .) get a pump machine and pump it out (like the kind most mechanics use)

2.) the easy way

• under the transmission is a bolt to the oil pan..
  
• unbolt it,, the transmission oil will come out.. (this bolt is actually a flush plug)
• when its all drained out tighten back the bolt and fill it with new fluid.. ( 5 - 6 quarts)
• easy as that .. good luck
  

probably a freeze plug

Okay this is a internal problem in the transmission you will need to remove side cover and oil pan of the transmission.This is a big job to do it safely you will need a hoist and engine cradel this a profesional job my advice to you unless you have done this before 2 or 3 times take it in for service this is a delicate job mistakes can resault in costly mancanical further repairs.Hope this helps,John

open the pan bolt on oil pan and drain all the oil.reinstall pan bolt. it is a 5/8 6 point socket,or 5/8 wrench.then you need an oil filter wrench.turn counterclockwise looking at the bottom of the filter.make sure the gasket is attached to the filter.,and not still on the car....install the new filter,putting a layer of oil on the gasket first.tighten till contact,then one turn.do not overtighten .fill with 3 litres and check the stick. keep adding until the full mark. start the car and let run 10 seconds,look underneath and make sure it is not leaking.
let sit 2 minutes and check again.the filter uses about 300ml,so top up til full and your'e done.
wipe up any excess around the pan bolt and filter.

I believe these are internal you must drop the trans. pan down to access it.

do you see a leak anywhere on the ground under the car??
check the oil and make sure it is not mixing oil and water

Cut that out. Replace it with a compression fitting. Bleed the system.

1999Mercury Sable died...acts like battery dead or alternator, however with key off there is a click, click sound and as soon as you giggle ignition and make sound stop ...there is power but as soon as you turn key on it all goes dead again.. battery takes a charge and don't think its an alternator problem.. think it is a relay switch...possibly the windshield wipers.. have noticed that the wipers turned on for no reason a couple of times and once again when I was messing with this situation