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Thread: Pretty Bad Oil Leak

  1. #1
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    Pretty Bad Oil Leak

    Picked up a 2003 525i yesterday for my girlfriend. I was told that it had a bad transmission leak. Today I decided to look into a bit. At one point I started the car and while it was running for about 15-20 minutes I noticed a rather large puddle of oil underneath. I jacked the car up to get a closer look. As I was about to go underneath I noticed a Low Oil Level Shut Engine Off warning in the cluster. So I did. Once I got under it appeared to be engine oil and coming from the area where the engine and trans meet. Naturally I thought the it was the rear main seal. But I figured I’d ask here to see if there is a common issue or if someone else had a similar issue. It doesn’t appear to be a valve cover or head gasket because those area appear to be clean. But I could be wrong. Any help would be greatly appreciated!!

    Thanks in advance!!

    Also, the odometer reads around 157,000.


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    Last edited by JasonMHorn; 06-22-2019 at 05:35 PM.

  2. #2
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    From your description it sounds like a rear main seal. Unless you have an inspection camera, sounds like trans needs to come out.

  3. #3
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    Upon a little further investigation I found that not all of the valve cover bolts were tight. So I plan on doing the valve cover gasket today. I don’t know if I can be so lucky but I’m going to start with that for now. I sprayed everything down with degreased yesterday, so we’ll see.


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  4. #4
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    How are they not all tight exactly?

  5. #5
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    The rear main seal is rarely the problem. Fluid pouring from that area is usually from the front bushing on the automatic transmission spinning in the case, resulting in pressurized oil spraying past the (still intact) seal. A minor drip is usually engine oil from a failed oil filter housing gasket or *cracked* valve cover. Both of those oil leaks follow the oil pan gasket to the low point of the right rear, where they misdiagnosed as the pan gasket or rear main seal.

    A bad valve cover gasket usually results in oil dripping on the exhaust, which produces mostly smoke and sometimes smells more like burning rubber than hot oil.

    The valve cover gasket nuts don't loosen on their own. They are designed to bottom out, with the pressure being applied by the rubber washers. Tightening past snug will result in tearing out the threads on the soft aluminum head. It's likely that you have misdiagnosed the problem.

  6. #6
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    Quote Originally Posted by jclausen View Post
    How are they not all tight exactly?
    A few of the bolts I was able to turn with just a socket.


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  7. #7
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    Quote Originally Posted by djb2 View Post
    The rear main seal is rarely the problem. Fluid pouring from that area is usually from the front bushing on the automatic transmission spinning in the case, resulting in pressurized oil spraying past the (still intact) seal. A minor drip is usually engine oil from a failed oil filter housing gasket or *cracked* valve cover. Both of those oil leaks follow the oil pan gasket to the low point of the right rear, where they misdiagnosed as the pan gasket or rear main seal.

    A bad valve cover gasket usually results in oil dripping on the exhaust, which produces mostly smoke and sometimes smells more like burning rubber than hot oil.

    The valve cover gasket nuts don't loosen on their own. They are designed to bottom out, with the pressure being applied by the rubber washers. Tightening past snug will result in tearing out the threads on the soft aluminum head. It's likely that you have misdiagnosed the problem.
    I did find some oil on what I’m guessing is some type of heat shield over the exhaust manifolds. That’s another reason why I opted to replace the valve cover gasket. I did it the other night and I haven’t had a chance to mess with the car again. I’m hoping to today.

    I don’t think it a trans leak because the fluid looks like engine oil and not trans fluid.


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  8. #8
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    I went out today to see if the valve cover gasket had fixed the issue. I added a quart of oil and started the car. Immediately the oil started dripping. IMG_1726.jpgIMG_1728.jpg


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  9. #9
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    It is probably the oil pan gasket. Check and replace both the upper and lower oil pan gaskets.

  10. #10
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    reach around the back of the head with a paper towel and wipe to see if theres any oil there. if so, VCG didnt take,

  11. #11
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    Quote Originally Posted by Chedley View Post
    It is probably the oil pan gasket. Check and replace both the upper and lower oil pan gaskets.
    I appreciate the input but it’s not even close to the oil pan.


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  12. #12
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    Quote Originally Posted by mattmar1 View Post
    reach around the back of the head with a paper towel and wipe to see if theres any oil there. if so, VCG didnt take,
    The valve cover gasket definitely held.


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  13. #13
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    Pretty Bad Oil Leak

    Just a little update, it’s been very hot here lately so I haven’t been working on the car as much as I’d like. Especially after working 10 hours in the heat at my day job. Little by little (mainly in the evening when it’s cooled down a little I’ve managed to almost get the trans out. I’ve dropped the exhaust, heat shields, driveshaft and I’ve taken out most of the bolts connecting the trans to the engine (I believe that I have two left). Hopefully within the next day or so I’ll have the trans dropped. Pending the weather obviously.

    I would also like to say, I personally think that it’s amazing just how well engineered these cars are. Everything seems to have its place.


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    Last edited by JasonMHorn; 07-04-2019 at 10:01 PM.

  14. #14
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    Quote Originally Posted by JasonMHorn View Post
    I appreciate the input but it’s not even close to the oil pan.


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    That's usually how it is when Chedley gives his best guess on what the issue is....
    Set the controls for the heart of the sun

  15. #15
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    Don’t forget the little 10mm that bolts into bell housing from the Engine block side of the car below the exhaust manifolds

  16. #16
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    Quote Originally Posted by BimmrMeUpSnotty View Post
    That's usually how it is when Chedley gives his best guess on what the issue is....
    lmao


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  17. #17
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    Just another update, yesterday evening I messed with the car a little more. I removed the last two bolts that I had. I also remove the fan so that I don’t break it when I lower (tilt down) the trans. I watched a video and it seems that I have 3-17mm bolts to remove. They have to be removed in a little hole next to the exhaust manifold (which appears to be in the way). I ran out of day light so I’ll have to try to tackle those bolts another day. Does anyone have any advice as to how to get them out with the manifold in the way?


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  18. #18
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    Another update:

    I was able to get those three 17mm bolts out and I finally got the transmission out! Now the problem is I don’t see any signs of where the oil was coming from. So I need to do some investigating. One thing I did notice is that the torque converter is loose. Like I’m able to wiggle it, is that normal?


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  19. #19
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    yes torque converter should be loose. it will slide of if you not careful. It's important that it fully seats when reinstalling.

  20. #20
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    Pull the torque converter out and inspect the seal. You shouldn't see any evidence of leakage, beyond a fresh drip or two from the removal.

    If the seal pulls out with the torque converter, you have an oil pump bushing failure.

    Check the "nose" of the torque converter. Note the two lugs. Look in the hole, and note where they engage.

    Practice putting the torque converter back on, rotating it until you feel it fully drop into place. There will be a initial engagement, then it will drop further as the lugs engage. Do a few times, and measure how far down the torque converter is when it has fully seated.

    This should only take two or three minutes. It's no big deal. But not fully engaging the lugs is a common, expensive screw-up.

  21. #21
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    Quote Originally Posted by djb2 View Post
    Pull the torque converter out and inspect the seal. You shouldn't see any evidence of leakage, beyond a fresh drip or two from the removal.

    If the seal pulls out with the torque converter, you have an oil pump bushing failure.

    Check the "nose" of the torque converter. Note the two lugs. Look in the hole, and note where they engage.

    Practice putting the torque converter back on, rotating it until you feel it fully drop into place. There will be a initial engagement, then it will drop further as the lugs engage. Do a few times, and measure how far down the torque converter is when it has fully seated.

    This should only take two or three minutes. It's no big deal. But not fully engaging the lugs is a common, expensive screw-up.
    I appreciate the help. I was able to get the TC off after playing around with it for a bit. Once I did so I look at everything. I noticed that when I tipped the transmission forward, oil would leak out. I drained the trans oil prior to removing it. I would imagine if I didn’t, the amount of oil that would come out would be much worse. Here are some pictures of what I’m talking about. What are you thoughts?
    IMG_1755.jpgIMG_1757.jpgIMG_1758.jpg


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  22. #22
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    The transmission retains a few quarts of oil even when the pan is drained. As long as the seal was clean and dry when you pulled the torque converter, it's still good. Of course a new seal is only a few dollars and it's trivial to do, so it's worth replacing it. But you don't need to, if waiting for the part would delay your project.

    The torque converter will also retain a few quarts of ATF. Even after pouring out the oil, you can leave it out in the hot sun and more will appear, sometimes overflowing.

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