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Originally Posted by hectorh
- Here is a link to high-res pictures: https://www.hectorh.ca/4runner/valves/
- Fingernail test: feels smooth like glass, however the lobes on this side have a dull appearance when compared with the other side which is shiny like a mirror
- Other than the dull surface, some of the cam lobes show oil staining. Is this a sign of excessive valve clearance? See https://www.hectorh.ca/4runner/valve...608_213641.jpg for an example. That stain is embedded in the metal, rubbing with a paper towel does not clean it off.
- I do have a borescope, is it worth removing the spark plugs to check the cylinder walls?
- I have not changed the oil yet and the last time I did an oil change (8 months ago, after dirt road season was over), I did not notice any debris in the oil
- No, I have not had the oil tested. Is it a good idea to do so in this situation?
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Ok, thanks for the pics . . . the fingernail test or even using your finger is a good litmus test to determine whether a cam lobe has wear beyond specs. Smooth like glass passes litmus test, though test all lobes.
A dull cam lobe is fine here because the major issue with debris is streaking on the lobe. Not uncommon to have one cam flank (closing/opening) differ in visual appearance from the other with various factors, I would not be overly concerned about it as long as the cam does not have any visual streaks and passes finger test.
Excessive or out of spec clearances between the valvetrain and camshaft can manifest in oil stains, though a quality engine oil with additives usually help with the oil stains. Its a varnish at this point and not much of a concern IMHO. Best bet is to use a high quality engine oil (synthetic as you are using) and shorter oil change interval . . . 5-6k mi maybe. Its what I tend to do on my 4R.
If you are thinking of selling your rig over this issue, then maybe piece of mind might be worth the trouble in pulling a coil and plug to borescope a cylinder. At this point if you didnt feel any issues with the cam lobes, the oil probably did its job and put particles in suspension and into the bottom of the oil pan.
I normally do an oil change on conditions, mileage or time, but given you are concerned with debris, might be worthwhile to drop the oil and collect some of it to send to an oil analysis lab like Blackstone. Not expensive, but if you didnt see debris 8mo ago and if you do one now without seeing any debris then maybe you just had debris build up at the inner edge of the valve cover flange.
Bottom line oil changes are cheap, oil analysis is cheap, borescoping a few spots takes half an hour at most, but a new rig usually not the cheapest. My assessment anyway.
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Some follow up questions:- To clean the cam tray, I'm assuming a clean rag or paper towel is the recommended method. I must not apply any type of cleaner or solvent in there, correct?. Would it make sense to use oil to try and flush the dirt out from places I cannot reach with a paper towel?
- After I finish with the valve covers, I will do an oil change. Should I do a second oil change after a short drive up to temperature? or just shorten the oil change interval until the next oil change? I use Toyota filters and synthetic oil.
- Would it be a good idea to drop the oil pan and clean it?
- If the oil staining on the lobes indicates a possible excessive valve clearance, the FSM has me remove a bunch of parts from the front of the engine to gain access to the timing belt and then rotate the engine to TDC. This is a far bigger job than I'm ready to do at this time. Is it urgent to measure the valve clearance or can it wait until I replace the timing belt in the Fall?
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Id vacuum it, use shop towels and some engine oil to clean it. Then maybe hit it with some compressed air. Stay away from solvents, flushes, cleaners and the like. Ive seen ATF as a detergent or a way to shiny up the engine, but Id pass.
I would not try to flush out dirt with oil, stick with what you can see or feel and go with that. There is a point where efforts diminish with a head in situ. The oil circuit under operating pressures and the additives to oils do a pretty damn good job of trapping fine debris and dumping it in the bottom of the oil pan like the stuff from a dirt road.
Oil changes . . . do one and see if the oil shows anything. Cut open the filter and check the pleats of the media to make an assessment, but my guess is not likely as this stuff tends to drop to the bottom of the oil pan. Id only drop the pan if this came back with some significant findings of external debris or metal.
Id hold off on checking valve clearance unless you are willing to take the approach of gauging what you can and running an analysis of whether that one or two measurements demonstrates clearances so far in excess of specs, or just deferring it to the timing belt.
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