Strange oil seep/wet spot

Hello, new member here with first question:
2020 4runner, all stock, 6k miles. I noticed a wet spot on the valve cover and looked a little closer, I removed the bolt circled in red and found the bolt hole in the valve cover about 1/3 full of oil. I asked the 2 Toyota dealers how this hole could fill with oil and one said it could not fill unless oil had been "splashed" near the bolt head, from above. The second dealer seemed to not believe me and said in so many words that I was crazy.

I cleaned out the hole with q-tips, re-assembled and ran it for another 300 miles. I also ran the engine without this bolt and did not see oil purging out. I checked again yesterday, stuck a q-tip in the hole and there was a little oil in there, less than a drop and just enough to wet the q-tip a tiny bit. I honestly can't say if it is still somehow slowly filling with oil or if what I found is residual from the first time. I cleaned it out pretty well the first time.

My question: Is it possible that somehow the hole is filling with oil from below, a pinhole in the casting or some other freak? This seems hard to believe since the casting that surrounds the threaded hole stands proud of the valve cover. I also would not expect pressurized oil below that bolt hole forcing oil up and into an imperfection in the casting.

 

I had the same exact problem. I removed both of those bracket bolts and reinstalled bolts with a coat of red high temp RTV. No further issues.

I think when they machined the holes, they went a little too deep on the one and it allowed oil seepage.
Very simple fix.

 

Here’s the link to my thread on this.

https://www.4runners.com/threads/oil-sweat.26075/

 

Yes. Looks exactly the same. Still seems strange that this bolt hole would be pressurized with enough oil to fill it and blow past the bolt head and up the bracket. If the hole is simply machined too deep then why would it hold oil? Seems like it would drain out when the engine is off.

 

Oil residue will remain regardless of drainage. I applied a thin bead of RTV on top of each bolt boss and under each bolt head before reassembly. But first I thoroughly cleaned the bracket, bolts and holes with isopropyl alcohol.

 

Do you know what is directly under that bolt hole, on the inside of the valve cover? I found this photo online, looks like there is a lug cast into the valve cover under that bolt. If this is under the bolt then that hole would need to be way too deep to break through under the valve cover. Maybe I am wrong here and that lug is not directly under the bolt.

 

If there is a hole/imperfection in the casting there, it could be drawn into the threaded hole by capillary action. So I bet no pressure would be required.

 

That was my thought exactly.
I just fixed the issue with some high temp RTV and monitored.
Good to go.

 

No clue, I fixed the problem and forgot about it.