M. Requin

Here's the situation: A little over a year ago we moved from our farm to a new place, and in the middle of the move the 928's fuel pump died. It has sat for a little over a year waiting for me to fix it. That's done,, and in the meantime the PS pump was starting to groan , which a simple rebuild fixed, and a new high pressure hose was fitted, A test drive after that worked showed the tranny needed attention: banging shifts, lurching in gear. A check of the reservoir showed that it needed fluid, so I got a filter kit from Roger, and did a change and refill. [Note: this is a high mileage car, over 240K out of which I've put over 130K since 2006, and the last 40K or so with a Mercedes 236.6 qualified ATF. I add this because I don't want this to become an ATF discussion, which might be more appropriate in other threads.] Another note is that I removed the quick fill adapter to reposition it- some clown in a previous filter change (I guess) turned it to the horizontal for whatever reason. So the return line from the cooler drained also.

The problem: I add oil to the cold fill line, start the engine and let it warm up, and the reservoir is then empty. When this first happened yesterday, I just added more ATF, but start, run through the standard routine which I have done any number of times without a problem,- oil reservoir empties after warming up, but after cool down it is half full.
I hesitate to continue until I have a better understanding of what's going on, so I am very much hoping the collective forum wisdom will save my butt here. In other words, HELP!

Kevin in Atlanta

You check the level when the car is running. All the ATF drains back into the pan with the engine off.

So you need to add ATF as the car idles until the fluid is at the maximum line. Run the transmission through the gears and continue adding until it maintains the maximum level.

You need to be sure the reservoir cap is on or the ATF will spill out.

M. Requin

Thanks Kevin, I know to check it when the car is running, what I worry about is the amount that drains back into the pan after shut off. And I'm using (at last) the trick little quick fill port, so no reservoir cap to worry about.

Thanks for clarifying my thinking! I'll post results.

M. Requin

New symptom: cannot add ATF through the fill port, it seems as if there is enough pressure to keep the ball bearing in the closed position (again, followed the routine in the WSM). However, the instant I shut the ingine down the ATF from my pressure filler start flowing to the reservoir. I'll try starting it again, using the WSM procedure for adding ATF as always,, and see if it behaves more normally. My only working theory is that there is a minum requirement for ATF volume under which it just don't work well.... Ideas anyone?

Mrmerlin

position the fill port as it should be,
start the engine,
remove the cap and add fluid via the tank.
Check the level; With the engine idling

Jason89s4

I second Kevin and Stan. FYI what you are observing does not sound out of the ordinary so far. You just have to be patient and fill while running and worry about the level while running at temp. Ignore level when cold or not running. It will rise as you’ve noticed.
I use the handy port to fill, but I’ve always used a pump. I’ve never had any issue with the check valve (ball bearing) closing on me. There is no tranny pump pressure in the pan. The check valve is just to keep it from leaking when you are swapping the connection for the cap.

M. Requin

Thanks gents. Stan, I did reposition the fill port. And Jason, I do use a pump, actually a Motive with a pressure gauge so I can keep from blowing the fill tube off the fitting- don't need that mess!
And I think the comments you both, and Kevin, made are spot on, Especially "remove the cap and add fluid via the tank." That will solve, if not explain, the "back pressure" problem. Back to work.

Speedtoys

I fill via the plug and a motive pump, no isues.

M. Requin

When I was younger I sometimes didn't think hard enough when I tried to solve a problem, and now I tend to overthink too often (I don't think there was ever an optimal middle period when I thought "just right"). This episode is a great example of my tendency to overthink things, or simply perseverate. So back to basics, and all is well. Thanks Stan, and Kevin, Jason and Speedtoys, too.

Kevin in Atlanta

BTDT

Speedtoys

Happens man..ive talked myself right out of which way a bolt turns it seems like sometimes too.