Black "line" of oil at top of dipstick hashmarks?

[SOHCman]

This is on a late 90s 351W with nearly 200k, running quaker state high mileage at the moment. I have been doing a series of short flushes with a variety of syn/conv to try and clean out crud left from the previous owner probably not changing the oil often.

Overall, the entirety of the oil turns dark quickly in an OCI, but I notice that right after changing oil I get a thin black line of dark, perhaps sooty oil right at the top of the hash-marks when checking the level on a cold engine. below the line is normal honey colored oil like you usually get in the days after a change.

I figure if it were cleaning carbon from inside the engine, it would uniformly darken the oil, but with it being on top, it is some sort of carbon dripping down from above and staying on top of the oil. Then when I check the engine cold before starting it the black line shows up.

Tis is a 90's engine, so on the list of carbon suspects are 1. the EGR system, which fills the intake manifold with black carbon. 2. the PCV system. 3. Perhaps there is burnt oil getting cleaned up under the rocker covers dripping down over night. And finally, 4. would a leaking injector wash combustion chamber carbon down and leave a black layer suspended on top of the rest of the oil?

Changed spark plugs and all were old, but within spec and indicated normal burn.

Anyone ever ran into this before?

 

[Kuato]

Might be the new oil floating old dirt to the top from some nook somewhere. I've saw something similar on an older (70s) vehicle I bought used; that vehicle got frequent oil changes for quite awhile.

edit: any chance of pictures?

 

[SOHCman]

I'll try and get a pic.

 

[SOHCman]

It is similar to this, with the dark at the top of the full range, and normal color below.

I this pic though, that looks more like varnish. On mine its darker black, and wipes off clean on a paper towel. You can see the black/tan difference on the paper towel even.

 

[SZR48207]

Carbon blowby? A 200k mile engine won't be perfectly sealed...

 

[SOHCman]

Originally Posted By: Reddy45
Carbon blowby? A 200k mile engine won't be perfectly sealed...


Would that sit on the top of the oil?

 

[CT8]

That is of no concern. I have seen that like on many Ford dipsticks. I used to work at a fleet repair company.

 

[Olas]

Carbon should be suspended IN the oil, not on top of it. 2 rounds of aggressive flushing and temporary blocking/diverting the egr&pcv will give you a clean base to monitor from.
Are all gaskets good?

 

[CT8]

Where is the exhaust manifold in relation to the dip stick? After a long drive feel the area .

 

[meadows]

CT8 +1

 

[SOHCman]

Slight weep/leak at base of oil dipstick tube, I believe it is the threaded kind into the block above the oil pan.

The exhaust is the stock manifolds, and the dipstick tube is bolted to one of the manifold bolts/studs. It sits perhaps 3 inches away as it passes up by the manifold.

Feel the area for what? a crack? It will be rather hot to touch after a drive as its bolted to the manifold.

 

[SOHCman]

Originally Posted By: CT8
Where is the exhaust manifold in relation to the dip stick? After a long drive feel the area .


I double checked, the dipstick tube actually weaves between cylinder 7 and 8's manifold runners right by the head, then down into the side of the block above the oil pan.

I felt around the exposed part and it felt dry and solid, although I'm not perfectly clear what I was looking for.

 

[SOHCman]

Originally Posted By: CT8
That is of no concern. I have seen that like on many Ford dipsticks. I used to work at a fleet repair company.


Did you ever confirm a cause, or was it just a common occurrence?

 

[MDettling]

Seen that on some of my 33 cars. Just grab steel wool and get it nice and clean, then monitor it from there on?

 

[SOHCman]

Originally Posted By: MDettling
Seen that on some of my 33 cars. Just grab steel wool and get it nice and clean, then monitor it from there on?


Sorry, that is just a representational photo similar to what it looks like. The oil all wipes off clean, but the oil at the "top" is dark like that photo as if it settles on top of the oil. There is no varnish, just a line of dark dark oil only at the top of the full range.

 

[Superflop]

Check your dipstick for leaks at the full line

 

[SOHCman]

Originally Posted By: Superflop
Check your dipstick for leaks at the full line


Oil is weeping from where the tube threads into the block. The oil pan gasket is kind of leaky to, could that be... what, pulling junk in under manifold/block vacuum?

That's no fun to imagine.

 

[ToadU]

If it runs and drives well don't worry about it. It's an old engine, well worn and still going strong. What's the worry? The engine is past its design life expectancy so every mile is a bonus at this point.

Please reconsider your aggressive flushing of the engine. I firmly believe it does way way way more harm than good. I have seen this in my own service department. Gunk is normal on an older engine and so is carbon.

 

[SOHCman]

Originally Posted By: ToadU
If it runs and drives well don't worry about it. It's an old engine, well worn and still going strong. What's the worry? The engine is past its design life expectancy so every mile is a bonus at this point.

Please reconsider your aggressive flushing of the engine. I firmly believe it does way way way more harm than good. I have seen this in my own service department. Gunk is normal on an older engine and so is carbon.


Im not doiny any auto rx or chemtool in the oil, just good oil and filters. I agree, t would be great to take it to 300k.

 

[ToadU]

Personally I'd change the oil at this point every 12 mos or 15k miles