Oil comes out of breather on top of tranny

Asked by Nov 30, 2016 at 10:01 PM about the 2003 Mercedes-Benz E-Class E500

Question type: Maintenance & Repair

2003 E500,  150 k miles. Had antifreeze in tranny. Replaced radiator and rebuilt the tranny. No leaking when not moving but when in gear fluid comes out of the top of the transmission at the breather. Shifts OK.

8 Answers


So it is either overfill or the tranny is running too hot. Did you check the cooler lines for any kinks or getting crushed during the repair work? I'm not a Mercedes man but from what some of my shop owner buddies have been saying is to bypass the radiator cooler and add on an auxiliary cooler out in front, they say that some of the rebuilders won't honor any warranties unless this modification is made. HTH

1 out of 1 people think this is helpful.

Well it didn't have too much fluid in it and it kept doing it till there wasn't enough in it to show on my dipstick. The lines are all in good shape with no kinks. I did hydraulic repair in the Air Force a few years back. It was driven very gently so it wasn't over heated. I can get it to leak if it is up on my hoist and a helper is in the car giving it a little gas. There is a new contact plate in it so there is a new float valve with it. The car is a 2003. Jerry


So if it does it even when cold then it sounds like the rebuilder may have forgot a baffle plate inside the tranny.

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The transmission is a 722.6. No baffles inside any of those I have done. I filled it up to the proper level using the Mercedes dipstick and when I started it up it blew some oil out of the dipstick tube. Cap wasn't on it at that time. I never had oil come out of that tube before on any of them I have worked on. I put the cap on and ran it for less than a minute and had a mirror where I could see the vent and it started bubbling oil out the breather vent.


Every time I have ran up against a tranny that is blowing fluid out of either the dipstick tube of the vent there has been something wrong internally if the cooler was in good shape. Even had one customer that caught his car on fire due to the same problem.

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Could it be that not enough endplay would be causing the problem?


That usually makes more heat due to more friction, but you said that it didn't get hot so now I have no idea.

1 out of 1 people think this is helpful.

I think there must be a hot spot in there that is boiling the fluid and creating a vapor. It may be too much pressure on a thrust bearing. I am thinking strongly about pulling it down and checking all those bearings and look for signs of over heating.

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