2002 4.7L V8 Tundra, new valve cover gaskets, tube seals, and spark plugs installed @ 186,000 miles. The cams and underside of the valve cover on the side with the PCV valve have a light bronze tinted stain. The cams and underside of the valve cover on the side without the PCV valve look new, and there is no varnish to be found on either side. The engine runs great and there are no problems, but what cased the oil stain?
A new PCV valve and grommet were also installed, and I have pictures of the staining, if only I knew how to share them.
Thanks.
How to post a photo:
https://carkiller.com/scottykilmer/qa/read-this-first/#post-183035
Pictures are up
I wouldn’t worry about it
I am not worried about it, I am just wanting to know what caused the stain.
Can anyone answer that question?
It's the inside of an engine. It gets covered in oil and dirt and then the heat bakes it on. It's not supposed to look shiny and new.
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My guess would be that since the PCV valve is only on one side, there will be small differences in temperature and pressure in the two valve covers, and probably some vapor currents as well. The vapors just condensed more on one cover than the other and that's why you're seeing differences in color.
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If you can't sleep due to this condition, and absolutely need to get to the bottom of it, then you will have to call Toyota and ask an engineer to explain it to you.
That's pretty much normal. Oil breaks down over time and the more volatile fractions evaporate. The valve cover is a relatively cool surface, which causes the same components to condense and form a film. Oil also splashes around under that valve cover, hence you noticed it was leaking.
Oil.
I am asking about the internal oil staining on the PCV valve side, and yes both VC gaskets were leaking... that's why they were replaced, and that's how I know there was staining just on one side.
VC with PCV valve
The internals under the VC are stained the same color:
VC without PCV valve:
The internals underneath the VC without the PCV valve:
Pictures have been added