Fixing an Oil Leak: 2009 BMW 328xi

  • Thread starter KodyWallice
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May 7, 2021
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For the past year, we’ve had a very elusive oil leak somewhere around the engine of our 2009 BMW 328xi. In general, I’m a very mechanical person, so I have to tell you that it was extremely frustrating not being able to find the source of the leak. Basically, everything around the front, driver’s side of the engine was wet with oil. The odd thing was, the car never ran low. During the entire year the leak occurred, I only had to add oil once. That was only half a quart. So, something was causing the front corner of the engine to get wet with oil, but it wasn’t a constant flow. If it had been constant, I would have had to add more oil as time went on. Strange.

A few days ago, I formed a great idea. I told my lady that we should clean the engine with some Simple Green and then let it run until we see something seep out of somewhere. If we could get rid of the old disgusting oil that had accumulated on all the aluminum, we’d definitely have a better view of what was going on. My gut instinct told me that the culprit was either the oil filter housing or the valve cover. Both of these areas are close together and neither one would be tremendously tough to fix. Take time to fix – yes. Something I couldn’t do – no. I can do it all.

Because of this great idea, I decided to grab the flashlight and go outside to the car. My plan was to stand there with the hood up and look at nothing and everything at the same time. I do this a lot when I think and I needed the flashlight to look behind all the nooks and crannies. It was a chilly morning and the car hadn’t been driven yet. This means the engine was cold.

A few minutes later, my lady joined me. I like to ask for her perspective because I oftentimes get locked in tunnel vision. She’s a genius and has saved me a number of times. It’s wonderful to have someone with such a different type of mind so close by.

As we stood there, I pointed out what I thought was happening. The oil was covering various parts, but only up to a certain point. I explained that the oil filter housing gasket was probably the cause, because the “wetness” only reached half way up that particular part. She seemed to agree. Then, for some reason, I started the car. She gasped and this is what I saw upon returning to the engine.


After she gasped, I gasped. What in the world? By the way, it’s the oil filter cap the leak is stemming from.

Here’s the deal. I’ve watched this engine run a thousand times and have never seen this. The thing is, every single time I’ve watched the engine while the car was on, it was after we drove around somewhere. The engine was hot. Because of this, I suspect, the aluminum had somewhat expanded, sealing the leak. So when I looked closely, I didn’t wee anything. Just wetness below that area. Now that I witnessed what was going on with a cold engine, I saw something totally different. This would explain everything.

I knew what needed to happen. I had to purchase a new oil filter, which would come with a new o-ring set and a copper crush washer for the drain bolt. I also needed to purchase some fully synthetic oil and a torque wrench to tighten the drain bolt with. I’ve never changed the oil on this car and have never owned a torque wrench. Since everything is aluminum on this engine though, I really didn’t feel like stripping out the bolt threads. Plus, torque wrenches are really cool.

This morning was the chosen day for this project. I received the last bit of everything yesterday and the temperature was forecast to be over 40 degrees. Bearable for me to be laying on my back outside.

The first thing I did was to loosen the oil filter cap and remove it in its entirety. For those who don’t know, this is what it looks like with that cap gone, with the inside of the oil filter housing exposed.


And here’s what the old oil filter looked like.


The strange thing is, when I tried to remove the filter from the cap assembly, the rubber part of the filter crumbled. I’m guessing this happened because the filter was so old. We really don’t drive much and the last time I had the oil changed was a while ago.


For those of you who are interested, this is what it looks like inside the oil housing cap.


To begin the repair, I cleaned the inside of the housing carefully. I wanted to make sure there was no dirt in there and that there were no cracks or anything.


Then, I cleaned the entire cap with some hot soapy water in a bucket. I wanted everything spotless for the new filter. By the way, the filter kit part number is 11427566327.


I got this online for around $12.

After everything was clean, I put the filter in the cap and changed both o-ring gaskets.


I also coated both o-rings and the inside of the housing with some old oil to make it easier to screw the cap back on.

Finally, I replaced the cap and tightened it to 18 foot pounds of torque. This torque specification is the same for the drain bolt.


I’ll tell you one thing, tightening this cap down wasn’t as easy as I thought it was going to be. That o-ring is fairly bulky and squeezing it into place took some effort. It doesn’t leak now, so I guess that’s the way it’s supposed to be.

That was the easy part. Next, I had to jack up the car and drain out the old oil.

Since I have a brand new jack, I was happy to get a chance to use it. I also have some sweet jack stands I purchased a while ago for times like this. I carefully jacked the car up and put about a hundred safety blocks in place.


I had the emergency brake on, both rear tires chocked, safety jacks in place and both front tires sitting on big 4×6 inch blocks. I also kept some tension on the floor jack. I felt safe enough to get under the car.

To access the drain bolt, I used a regular screwdriver to open up a small hatch in the plastic engine shield. If you look at the next photo, you can see all the oil covering the plastic from the leak. Boy, that’s ugly. We definitely have to bring this car through the drive through car wash to clean the undercarriage.


I used my new Dewalt socket set to remove the drain bolt. It happened to be 17mm. I let the oil drain into my huge GarageBOSS 16 quart oil drain pan.


While the oil was draining, I decided to clean that little plastic flap that was covering the drain bolt. I hate dirty disgusting things.


I also cleaned the oil drain bolt, removed the old washer and replaced it with the new one.


When the oil was finished draining, I replaced the bolt and tightened it with my new Tekton torque wrench. This wrench has a 1/2 inch drive and is good between 10 and 150 foot pounds of torque. It’s pretty sweet.

IMG_0422.jpg tekton-torque-wrench-head.jpg

When I was finished under the car, I lowered it down and added 6 quarts of some really sweet Castrol Edge fully synthetic motor oil.


The oil is about $5 per quart, but it’s what the BMW dealer uses for their oil changes. It’s also good for 15,000 miles, so I don’t have to worry about doing this again for a little while. Since we’ve only driven about 5,000 miles since 2013, it may be a long while.

Anyway, that’s how I fixed the oil leak that was coming from the oil housing cap on our car. If you’re attempting a project like this and need any assistance, leave a comment below. Thanks for reading!