Car Doc, you work on Japanese cars all the time. Question here for us shadetree mechanics: is it appropriate to use silicone goop at pretty much all the places where a thin paper gasket was used originally? This is what I have found on various used Japanese cars and now tractors where I was clearly not the first person to disassemble something. I can see where replacing paper with paper is more convenient if the part has to be opened occasionally, like Yanmar's hydraulic screens, but does it hurt anything to just use RTV silicone universally in place of all paper gaskets? What is considered 'standard practice' by modern professional mechanics?
Good question California what I try to do is use what the factory used and that covers me. However the silicone's available now days can hurt automotive oxy and air fuel ratio sensors so on a car an automotive type silicone is needed. CLEANLINESS is absolutely mandatory a spray of brakekleen and air is how I clean parts and that leaves a dry surface.
I happen to really like anerobic sealer and use it whenever I can on hard close fitting castings. It wont dry until you clamp it together so you can put sealer on your part and go to lunch and still assemble it just like you just put it on.
High temp automotive silicone is great and as long as a person puts
just enough on will work for taking the place of almost any gasket made up about 100 psi and not submersed in gasoline and used on hard castings, tin covers and lightweight parts etc takes a more careful approach.
What normal everyday mechanics do is overdo the silicone by a ton. It only needs to be a thin cote and what gets most folks in trouble is the excess gets loose inside the housing etc and clogs passages and filters and guys like me see that and cuss the "glue artists" as we attempt to do it right.
I smear it on both surfaces with my finger and that is like sticking tape to itself and very little oozes out or in fwtw. I hope I answered some of your question!
Oh one more thing I really stress is "sealer" that word is misleading to the un familliar in that a gasket will do what it was designed to do w/o sealer. As far as silicone it is a stand alone product and granted it can occasionally be used in conjunction with a gasket, anerobic only works metal to metal and in tight fitting parts.
I stress occasionally because the silicone will allow some gaskets to just slip out the side as long as a gasket is stuck on good real good a light film of silicone can and will do a nice job of filling imperfections and I do use it that way but as a rule never use silicone with a gasket!!!.
edit: on another note about gaskets I think the guy who came up with the idea to mix rubber with cork in gaskets should get some kind of award. they seldom use them anymore though I have to ask for them. that is absolutely the best valve cover and oil pan gaskets there are the rubber swells up and adds tension as long as they are not tighten to the point they squish out at the bolt holes that gasket will out last a straight rubber gasket 10 times before leaking. my .002
