Oil leak
 

I have a MCS convertible 2006 that has a very low key leak. In fact I bought the car last November and stored it for the winter (5 months ) and it actually only leaked twice on to the garage floor the whole time. Ever since I started driving it on a semi-regular basis it seems to leak more (2-3 drops per week). It seems to be seeping between the two parts (which to me looks like the junction between the transmission and engine oil pan but I could be wrong). My first instinct would be to tighten those two bolts, but I decided to stop trusting my instinct a long time ago and ask questions first. Does this look familiar to anyone? I know from previous records that the crank position sensor gasket was replaced less 2 years/ 7000 miles ago at the dealer. Any input at all would be very much appreciated.
http://postimg.org/image/rzdiigb4j/
https://www.northamericanmotoring.co...226_122133.jpg

Yup you've identified it correctly. That leak is likely the "rear main seal". Lots of info on it around. Not a cheap fix, but a necessary one if the drips are getting to you.

Make sure to check your oil often and top it up.

Thanks for the reply. Excuse my ignorance but would the rear main seal leak transmission oil or motor oil. I recently changed my transmission oil with redline mtl (which is red in colour). The oil I see leaking seems to be engine oil.

The engine is divided into two halves. The camshaft sits between the upper and lower halves. The rear main seal is a large circular O ring that seals the joint between the halves and camshaft. Look in the area of #3 on this image:

http://realoem.com/bmw/diagrams/b/p/146.png



That side of the block is where the transmission mounts to the engine. Assuming it is the rear main seal leaking; the engine oil is leaking out of the seal, down into the space between the transmission and engine block, pooling at the bottom and finding it's way out between the engine and transmission joint (your original photo). There's no way to stop it without taking the transmission off and replacing the seal (not an insignificant job).

Hope this helps

The seal looks like this beileve you are taling about on the engine bewteen the two halves of the cranksahft.

http://www.realoem.com/bmw/diagrams/d/y/310.png


#1 Crankshaft Seal Part # 11111492244

http://www.ecstuning.com/Search/SiteSearch/11111492244/

http://c1552172.r72.cf0.rackcdn.com/334109_x600.jpg


Thanks

I had a chance to jack up the car today and take a good look. I'm starting to think that my oil pan gasket might be the culprit. There was some oil accumulating on the rear oil pan bolts (pic link included), and logically the oil can work its way own to the lowest point. I will look around for a guide on oil pan gasket replacement but the a/c compressor and engine mount seem to be in the way of the oil pan complicating what should be a simple repair. Is this a DIY type of repair?http://postimg.org/image/l07q7tcn1/

Just an update for folks searching around these forums with a similar oil leak to mine. Changing the oil pan gasket solved the problem. I am now leak free (until I develop another that is). Changing out the gasket was not very hard but time consuming (service mode to unbolt the A/c from the oil pan). I could only find the long way DIY so it took me about 4 hours total. If I had to do it again I'm sure I can get it done in 3 hours or less. Only hiccup I encountered was that I snapped one of the engine pan bolts when re-installing the oil pan. I still don't understand why as I torqued (23 ft/lbs)all the bolts to spec (maybe a weakness in the bolt's metal?). I guess 12 out 13 bolts holding up the pan is enough as it doesn't leak at all......but it's still bothering me. My neighbor, who is a mechanic, checked it out for me and said not to bother with it.

Going from memory I thought the pan bolts were 17 foot lb...I would be surprised if 6 more would break it. Regardless, one shouldn't hurt. My pan gasket was dripping where you had described. I didn't use any sealer, as the Victor Reinz gasket had small ridges that provide extra sealing. I replaced it 50K ago and all is well, no leaks.

I've a mystery too. I have an '05, R52 convertible. The PS tank gets a light coating of oil on it. I wipe it away and it comes back. I don't see any obvious leaks in the area and see no drips on the floor.