GM5l40e transmission breather leaking ATF at times.

[riverjamie]

Hi Guys I know this is a X5 forum but our tranys are the same. Hope one of you might have had this problem and can share some thoughts.

I have an 2000 E39 528i 120k on it. My son gave it to me for something for me to do now that I'm retired. It's been a real labor of love to say the least. I've done alot of work myself, if you name it I've probably have done it.

So here's the problem. It leaks ATF out of the breather (which is located where the bell housing meets the main body of the trany. It's just a little metal tube with a floating metal cap on it) at times.

2000 bmw e39 528i 120k has GM5l40e trany. It does it mainly when it's cold and in reverse. I live near San Francisco, CA, USA so it does get to cold here, but the car is in the garage most of the time. I tried some SeaFoam Transtune (cleaner). Then did ATF flush through return cooler line and filter change. Seemed to go away for a while about 3wks. Then started in off and on.

It does not seem to do it if when cold if I start it in neutral, drive, neutral, then reverse. But can't be sure if it's doing it while driving?

After 3000 miles since ATF change it's lost about 6 ounces. I jacked up the car yesterday, warmed it up to correct temp 98 and opened fill plug, no stream, it didn't need much but still 6 ounces? Still not to comfortable with that. I was thinking about installing a extension tube, if I can, to the top of the breather and running it up under the hood to a reservoir tank. But not sure if the fluid will just go back down into the trany if when the pressure drops or not? If it just went back down into the trany that would be great. But I don't know if there might be a check valve?

I just can't see taking in a good working trany (no shift problems and smooth) and having the whole thing rebuilt for this.

Any thoughts, has anyone else had this problem? What about the pressure solenoid?

Thanks