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

[upallnight]

There is a specific procedure for checking filling the trans. You mention that you jack the car up, but did you jack both ends up and made sure it was level? I'm assuming that 98 temp is in F since you live in the States, but how did you determine the temp? Did you use software to communicate with the computer for the trans or did you just use a thermometer to arrive at that reading? Are you using BMW fluid or some other brand?

[riverjamie]

Car was up on ramps (Rhino in front and Jack stands in rear with tires off) I tried to level car the best I could. Temp was measured with a digital temp meter like you would use on yourself, on the bottom of the pan. I used Dexron 6 from Napa Auto it's a big Auto Parts supplier in the US. The old ATF was replace with Pentoisn Amber in color, which I found out was not the correct oil for this trany. It was pretty dirty when it came out. But supposedly the ATF I put in is compatible. It reddish in color. When I first filled the car 3k ago, I let it drain down to a small stream like it requires. When I opened it up yesterday it did not have a small stream at all. After 6oz it did. I was thinking about trying to install a tube that would either go up to the engine area to a reservoir tank or to a tank near the top of the trany. From what I understand race cars that have automatic's have a small reservoir tank installed because of the pressure that builds up.

Thanks for replying
River

[JCL]

There should be no need to install an overflow bottle.

The most common cause of fluid pushing out the breather is that the level was too high to start. If you leave it, does it stop pushing fluid out? And at that level, does it slip or drive fine?