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Discussion Starter · #1 ·
Recently bought a very low mileage 528. Last oil change by the former owner was last July and only 2000 miles have been driven since.
I was cleaning the engine today and I removed the oil cap. There was brown sludge on the bottom of the cap and on the rim of the cover.
Any idea what is going on ?

Car just turned 49,000 miles.
Thanks
 

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It's often caused by repeated short runs where the engine doesn't fully warm up and condensation in the rocker box isn't fully burnt off.
 

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Actually that pic is normal at 100K, not a cause for concern at all.

This is real sludge seen in this forum:

Now that is SLUDGE!!!

The brown stuff you see is indeed condensation from within the engine. The color ranges from brown to a thick yellow-white mayo-like sludge. It is present in virtually every e39 to varying degrees. It often means, but not always, a failing CCV. Replacing the CCV is a PITA and is a common component failure in e39s due to the poor design. The CCV is supposed to vent the crankcase (like a PCV) and allow this condensation to flow back into the sump but it gets clogged by an accumulation of this condensate. In colder weather, this condensate clings to the CCV pipes/tubes, as they do not warm sufficiently on short trips to flow back into the CCV. The BMW "fix" is insulated pipes/tubes, however, this is only a partial solution. Best to avoid short trips and allow the car to warm sufficiently.
 

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Discussion Starter · #9 · (Edited)
Thanks to all for replying. It does look like the photo above but with some extra **** (sludge) that I cleaned off and now the cap is just brown (looks like rust). As Fudman mentioned above it did look like brown to a thick yellow-white mayo-like sludge.
The former owner only used the car to go on short trips, usually 5 miles a day, to the train station. He told me that in the entire time he had it (11 years) he took only 5 or 6 long trips and the rest was basically daily to the train station. He only changed the oil once a year too by BMW.
So, I guess I will have the oil changed and use it more often now that I own it.
 

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I had an interesting thing happen with my wife's Ford F350 diesel. Because of the snow, we didn't run it at all during February. Once we got it back on the road, I drove it to town and back (less than 15 minutes total run time). After that trip, I happened to remove the oil filler cap and noticed a light-colored residue inside the cap, which I wiped off. After the next trip (also short), the residue had returned, but there was less of it than before. At that point, I changed the oil and took it on a long trip with a heavy trailer. Now the residue is gone.

I am not sure what that means for this thread, but I think it supports the condensation theory mentioned by the others here.

Seeing that residue on my wife's oil cap spooked me a little. Those Powerstroke motors are notorious for cylinder liner failures resulting from cavitation on the coolant side of the cylinders. It's a great truck, but I am always fearful of what I will see on the dipstick.
 

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Also, accelerated oil changes will get rid of that stuff in time.
I had some deposits when I purchased the car - it was maintained by the BMW interval. It was under the oil filler cap and on the dipstick. Then I took things in my hands and the first 2 oil changes were at something around 3000 miles, after that between 5 and 7 thou miles to day. The mayo and brown stuff is gone. Also, I had the CCV freeze on me a year or so after I purchased the car. No problems since. I also took a flashlight and looked inside oil filler cap and it looks great -what I can see. When I did the Vanos, what I could see was looking great too.
 

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Also, accelerated oil changes will get rid of that stuff in time.
I had some deposits when I purchased the car - it was maintained by the BMW interval. It was under the oil filler cap and on the dipstick. Then I took things in my hands and the first 2 oil changes were at something around 3000 miles, after that between 5 and 7 thou miles to day. The mayo and brown stuff is gone. Also, I had the CCV freeze on me a year or so after I purchased the car. No problems since. I also took a flashlight and looked inside oil filler cap and it looks great -what I can see. When I did the Vanos, what I could see was looking great too.
Like the picture of the crud with the valve cover removed?! No way. The only way to clean that is a tear down. No amount of oil changes, solvents, or magic elixirs will clean that up...it has been tried here, and other forums....just doesn't happen when it is that bad.
 

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Like the picture of the crud with the valve cover removed?! No way. The only way to clean that is a tear down. No amount of oil changes, solvents, or magic elixirs will clean that up...it has been tried here, and other forums....just doesn't happen when it is that bad.
I'm not talking about that fouled engine. I agree that nothing can remove that. When I purchased my car, it was still under BMW warranty, very low mileage, practically new. I was talking about my car which started to develop a mild sludge/mayo. The inception of the process if you will, not that graphic pic.
 

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like this?

Mine looks like this as well (73,000 miles); I use RedLine 5W30 change every 5000 miles, did the VANOS with Fudman and inside the engine looks mint (zero deposits) so I'm wondering if the oil condensate simply goes to the highest point in the engine (the cap). After changing my oil last week, I warmed up the car and rechecked oil to top off last 1/2 quart and noticed already small beads of moisture on the cap (clear at this point)... could be my CCV, I suspect it has never been changed (FL car).

I drive 24 miles one way to work so car gets a chance to warm up by mid-point in the commute daily; using my daughter's VW Golf now as my winter car but miss my e39.
 
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