Mile-o-matic blows fluid out filler on cold start
 

59 Edsel, 292 2v, aluminum case real 2 speed Mile-O-Matic (Ford-O-Matic). The car is all original and this is the correct "PBR" code transmission for the 292.

Sitting for 50 years. I had the trans out, fully drained it including torque convertor. It drained for a couple months while I pulled the valve body, cleaned everything, replaced servo seals, adjusted the bands, replaced front and rear main seals and reinstalled it.

I followed the factory manual on refill method and amount. Added 4 quarts, ran for a couple minutes, added about 4 more quarts, ran again, shift through all gears, check fluid level and filled to dipstick reading. Capacity is suppose to be 10 qt. I added about 9 1/2 total and the dipstick reading was near the top of the fill hatch.

The first couple of starts I didn't see any leaks. Then after sitting for a day or two I started it, ran the engine in park for about 2 minutes and turned it off (never put in gear). There was a big puddle of trans fluid under the car!

I've come to find out that after the car sits for a day or more it blows trans fluid out the filler tube on startup. The amount each time appears to be getting smaller but after about 10 times, it's still doing it. I was hoping it would find it's own level. After the first start of the day it doesn't do it again until it sits. When at normal operating temp in park the dipstick reads about 3/4 between the low and high marks.

The vent is high on the driver's side. It's base is round (not hex for unscrewing) with a loose tin cap over it. It's clean as far as I can tell. Is it just a pressed fit? How do you remove it with the trans in the car? Is there an easy way to remove the tin cap? It's not easy to get at.

I did check the dip stick after the car sits and the level is very high on the stick. Is that normal or is something leaking back into the pan that shouldn't? BTW, the trans will shift and move the car immediately after startup so I think the torque convertor still has fluid in it.

I'm hoping it will find it's level but also have a concern that if it drains back that much the pressure of the pump at startup might continue to blow fluid out even as the level drops until it is too low for proper operation.

Re: Mile-o-matic blows fluid out filler on cold start
 

I believe a fair amount of the fluid drains down into the pan when it's not running. Then refills the torque converter & passages when the engine is started.
Most automatics have you check the fluid level when the engine is idling and the transmission is at operating temp and in Park.
My first thought was the vent may be clogged or an internal part is getting stuck out of position.
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Re: Mile-o-matic blows fluid out filler on cold start
 

Most automatic transmission have a large enough quantity of oil that it expands to a higher oil level after the car has been driven and is completely warmed up. This can make filling a cold transmission a challenge and is the main reason that they want the oil level checked when the car is completely warmed up. I don't worry about what the capacity is if everything is working. I just make sure it is within the range when the car is completely warmed up. I don't even check it when it's cold unless it won't shift into gear.

I would suggest that you find a way to apply air pressure to the case and see if the air vents out at the vent fitting as it should. I don't think it was meant to be easily removable. The time to test is while the transmission is apart but it should still relieve air pressure while completely assembled.

Make sure that the fluid is coming out the filler and not somewhere else. I've seen them blow out fluid if the vent is plugged so that was certainly a logical thing to check.

Re: Mile-o-matic blows fluid out filler on cold start
 

To avoid any chance of damaging a seal with air pressure, just adapt a length of hose (like heater hose) to the filler tube and use lung pressure. Blow a breath in. If the vent is plugged, the air will come back out the hose. if the vent is OK you'll hear air coming out the vent.

Re: Mile-o-matic blows fluid out filler on cold start
 

The leak is from the fill tube. If I run it daily it will not leak enough fluid into the pan/fill tube to blow it out on startup.

Re: Mile-o-matic blows fluid out filler on cold start
 

Is it overflowing out of the top of the tube?
If the transmission isn't overfull that would be from internal pressure, being caused by some part of the transmission not working correctly.

I like 40 Delux's test suggestion in comment # 4