Hello,

Passing along an oil leak fix (finally)on the breather box.

Started a degrease campaign on the engine compartment a few months back and been tracking down and fixing small oil leaks. The area under the hood was a real oily mess after 22 years, a legendary clogged flame trap leak, and a poor job putting a valve cover on. One thing about changing over too and and running full synthetic motor oil is when it does leak makes cleaning that area a snap. Had what I thought was a rear seal leak for some time now and the valve cover had a couple of leaks for sure. Got a new cork seal for the valve cover and did the red RTV thing, and those leaks are a thing of the past. After more cleaning and degreasing found that another oil leak was in fact coming from the breather box. This is a 1986 245DL 233K by the way (AKA Inga). This was a new box installed over a year ago. Pulled it off and changed the oring and reinstalled the box. It seemed to get worse actually. This weekend I pulled the throttle body and replaced all those seals and cleaned it all over. Did that so I could see the breather box that was just a good time to do all that. Cleaning the throttle body, found a small leak in where the idle control knob adjustment meets up with the throttle body. Flame trap oil was working its way out and dripping down the knob. The paper seal was saturated, but not the cause of the bigger leak.

Pulled the breather box out and checked the surfaces on the block for pitting and the oring for any bad spots, found nothing. Made sure that the other seal was still firmly in place and not pushed down into the block, and it was all good. Pulled out another new oring, put it on the breather box making sure nothing was pinched, and declared victory Sunday night. But.... still had a small leak after my 72 mile commute to work and back Monday night. And yesterday afternoon it was working its way back up to the old leak levels. I was starting to get frustrated, this could not be that hard. Then got to thinking about the new breather box purchased from a dealer last year and wondered if that might be the problem. They did mention that the part number had changed on later year 240's and that was all they could get. But they looked like the same part and bolted right on. They said they had sold several with no reported problems. Pulled the old box out of the parts stash (had cleaned it out and stored it) and pulled the newer one off the car. Put the two side by side and started looking for any differences. The oring on the box was covered all over in oil by the way when removed. Looking at the two boxes all the plastic molded parts were identical in size and shape. But the new breather box had longer metal sleeves in the plastic where the two 13mm nuts go into the block that stuck out the bottom of the plastic. The old box had ones were flush on the top and bottom of the box. When you installed the 13mm bolts the longer sleeves on the new one caused the bottom of the box not to compress oring enough and that lets oil under the oring and out the sides of the box. At least that was what seemed to be the root cause. Installed the last new oring (good thing I bought two extra) and this time put it on the old box and bolted it back on. Took it down to the carwash and did a good cleaning one more time. Just checked it at lunch today and it is dry and oil free. And there does not seem to be any new oil dots on the ground also, and that is a first in long time. Still will check it for a couple of weeks but that seems to have been the problem.

So if you get one of those new dealer breather boxes on a older car, grind those silly sleeves flush with the plastic before you install it.

Regards,

Paul