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Discussion Starter #1
My 97 528i I6 auto with 255k miles has had an oil leak for years. It never left a puddle on the driveway. The oil pan gasket was always wet and the tranny pans were slick. Years ago I casually asked the mechanic and he immediately said the RMS. I don't know how he knew. He didn't drop the tranny or add dye to the oil.
Fast forward to today and the oil leak is worse. It leaves a small puddle on the driveway. I added 1 bottle of dye from O'Reilley and could never spot the leak. Bought a better UV light, did an oil change, then dumped in 2 bottle of dye. Still can't find the dang leak. Based on this forum and friends, here are my options. I even sprayed gunk where I could and shoved my hand w/ a rag everywhere else to wipe off what I could.

Oil filter housing gasket. Probably original. Lots of gunked up oil on the engine block in that area, but nothing is showing from the dye. Seen lots of posts here about this leaking. Pretty sure mine isn't. Not a bad DIY if I keep the bolt sizes straight, per cn90.

RMS. Probably original. Can't see it. I do see drops of oil thru the bell housing holes on the bottom to access the pan bolts. When I pulled the tranny last year I also took off the flywheel and saw oil, but nothing excessive. Assumed it had just migrated/blow back there over the years from the pan gasket leak. I could do the RMS DIY, almost did it last year. (Note to self, just do the RMS when the tranny is off).

Oil pan gasket. My mechanic says these never leak. Look at the RMS instead. The pan gasket is wet all the way around. Dropping the subframe doesn't sound like fun. Would copy mudbones approach and cut the gasket. Does a fully saturated pan gasket point to that gasket, or could it be the RMS leaking down, then wicking around the entire pan gasket?

Could it be the oil sending unit or some other "port" on the engine block that oil could be seeping from? Drive's side has more dirty oil than pass side. Again, I can't see any dye trails.

To maximize the dye, I've worn the yellow glasses, removed the front tires to see in from the sides, and did it at night so my flashlight was the only light source. Making matters worse is I have a small coolant leak near the exhaust manifold off cyl 6. So when coolant runs down the bell housing past the torque converter bolt access hole, then mingles w/ the oil, everything under the UV light looks like coolant. I think the coolant glows on it's own. I wonder if the coolant is contaminating my dyed oil. Can I stick an absorbant pad up there to catch the coolant? How and would it stay while driving and hot? Can I put the car on jacks and just run it in the driveway and repeatedly wipe away coolant?

In summary, if I rule out the areas of the engine that I can see, then I'm left w/ the oil pan gasket or RMS as the source of the leak. But I want proof before I start one of those jobs. Any advice? Am I doing something wrong w/ the UV dye? I'm not pulling the head to fix the coolant leak. Car isn't worth that much. It's small, I'm living with it.
 

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If it's the main seals you will only see oil in the lower part of the engine and leakage/drops forming right on the bell housing where it meets the block. But since you've said you're getting leakage on the side of the block you could have more than one leak.

Now if it were a valve cover due to how the engine is tilted you will see alot of smoke coming from the bay since oil will seep over the mani. Same applies to the head gasket. If it were the oil pan you would seepage at the gaskets and only the lower part will be sludged.

My guess would either be the oil filter housing where it meets on the block, vanos line or a broken vacuum line/ccv hose thats seeping oil onto the side of the engine, plus the main seal if your mechanic is truly correct.

Since you said you notice puddles of oil the leaks should be obvious to source. I would remove things to help find it, for example the drip pans under the engine, the air filter box and the hoses.
 

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I bet it's the oil filter housing. My 2003 x5 had this kind of leak. So I replaced the valve cover gasket as well. Both gaskets were brittle. Hard as glass. Oil filter housing gasket was a bitch.
 

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If the OFHG and VCG are original, in my experience owning 3 of these cars (all 528i's) I'd be pretty amazed they are NOT leaking some oil - but anything is of course possible. I ran my last 98 528i to 218K miles; it had an oil pan that was wet all-round for the 7 years I owned the car, the shifter (it was a 5 spd) selector rod seal leaked and likely the main seal too. I never had oil hit the pavement when parked however - I lived with it until I recently got a replacement car and sold this one.

I have never had to do what you attempting to do: find the leaks on a very old motor - seems that you'd need to get ALL the excess oil of the engine and tranny housing in order to sort this out and pinpoint the leak(s). This is probably not all that easy for the DIY person w/o access to a lift, and it seems a pretty dirty job.

May be the solution is to do what you've done....let it be. Put something under the car when parked to catch the dripping oil. As you said, it's an old car.

If you feel the leak is now at a point where it's really excessive, venture forth and clean off the engine/tranny as best you can and go from there. I'm sure the mechanic would be more than happy to remove the exhaust system, disconnect the driveline, disconnect/drop the tranny, etc. and fix your (possibly) leaking main seal - that's gonna cost some bucks. It's an old car...is it worth it? Only you can answer that one.

Good Luck/Bill
 

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first things first... degrees the **** outta that sucker.. and wipe it down... and then start watching for where it gathers...

Its simple observation... But once the thing is a rolling grease ball... Its harder to determine
 

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As well said, de-grease, completely!! Clean it from the top down, then get it up in the air and clean everything from the bottom up. Then clean it one more time! :)

Jim
 

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As others have said, it's most likely the oil filter housing gasket. When this leaks it flows down the block and gets blown backward by both the fan and air flow from driving to the point that you can't find the source. I changed mine and at only 105,000 miles and the gasket was hard, brittle plastic and was compressed about 1 mm. No resiliency whatsoever. I suggest you start there. I'm still getting a little oil leakage so the next oil change I will be replacing the oil level sensor gasket. I see some oil dripping from that point but again, it is difficult to identify the source.
 

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Discussion Starter #9
Thanks, all. The VCG was replaced last year, but that's <500 miles ago. This is my son's car and work in progress, so it's not getting many miles. I should have mentioned the VCG in my first post. I've looked around and don't see any leaks that high.
I do see heavy grease/dirt build up above the oil pan gasket on the drivers side. Makes me think it's not the pan gasket because I don't know how oil would leak upward.
What's the best cleaning method? Power wash at downtown wash bay? Spray with Gunk and hose it off? There are many areas I can't spray or get my hand in to to wipe, especially the OFH area.
 

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Most suggest a gentle cleaning, and not pressure, to avoid compromising electrical connections.

I find a good approach is via an orange cleaning solution, followed by a gentle spray from a garden hose, but you will need to get it up in the air.
 

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Discussion Starter #11 (Edited)
Update, and looking for more advice.
Yesterday I replaced the OFH gasket. Pretty easy, thanks cn90.
With the power steering reservoir, alternator, and OFH removed, it also gave me more access to that part of the block. All of the oil on this side of the block was hard, dried, and black gunk. Nothing looked fresh, even when I took the opportunity to scrub it off, except for some spots behind the vibration dampener. Contrast this w/ the fact that I have spots of fresh oil in my driveway. It's leaking, but the OFHG wasn't it.
I get 3 drops (edit: meant spots/circles) on my driveway, the largest one is in front, with 2 smaller ones 20" back. I have an I6.
Here's my theory. The largest spots on the driveway is directly below the main leak. The smaller spots are the effect of wind, wicking, etc, causing it to flow backwards. I'm pretty sure my oil pan gasket on the driver's side is the path. No smoke on the exhaust manifold side.
Searching the internet last night I zeroed in on the front main seal or timing case as new possibilities. I can't see because they are behind the vibration dampener (large toothed wheel) at the main pulley.
wgosma is probably right, I have multiple leaks. As this will be my son's car, he's learning, so why not dive in and fix everything, within $ reason. I'm not against pulling the tranny to do the RMS. I'm just not sure that's the source. Yet Simple Green, Gunk, scrub brushes, rags, gentle pressure from a water hose, and UV light still aren't making the source evident. I'm frustrated I can't pinpoint it.
1. RMS. But why would oil leak there and go FORWARD along the oil pan gasket? Doesn't make sense.
2. Oil pan gasket. It's wet on the driver's side and somewhere inside the bell housing it exits that seam and gravity takes over. Might drop the subframe (ugh) or simplify and do mudbone's 2 cut method. Or just let it be. 255K miles, don't want to make things worse.
3. CCV. Probably original. Need to figure out how to get to it. Could oil leak here, down the block, and then run along the pan gasket?
4. Base of oil dipstick tube? Again, why would it flow forward if leaking from there?
5. VCG, Vanos line off OFH, and oil leveling sensor on bottom of pan are dry.
 

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I would just leave it be.....
I have a piece of cardboard under my engine in the driveway, I see drops of oil on the underside of the pan but it is such a small amount I could not be bothered.
 

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Have heard nearly nothing about main seals leaking, by contrast, front timing covers leak all the time. As stated above, not sure if a couple drops of oil necessitate pulling all that stuff off to put a new timing cover gasket on. That's an, "only if it really bothers you," project.

Jim
 

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Well the drip pan flows back and downward so it can something wlse. I dunno unless I'm standing there or if anyone else is there with you all we can do is guess...

How bout some pics. If you can lift the car on ramps and take some overall general pics that may help.
Or if member here who lives near ya can stop by.
 

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If/when you do get underneath it to snoop around hit everything with some brake cleaner to clean off as much gunk as possible. After a few weeks get back under there and snoop around again to see if you can trace the source. Not likely it is leaking rearward and making its way forward. I would expect the opposite.
 
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