I’m beginning to wonder if chambers in the valve cover for the PCV system are restricted with sludge.
Tester
Tester: Regarding sludge in PCV chambers, I am doubting it. I cleaned off inside of valve cover when I changed plugs 13K miles ago, and I don’t recall a lot of buildup. Is there any way to test for such possible blockage with car not running, short of removing valve cover? Any additive that would remove such sludge once car is running?
It was easy to test for blockage in the PCV breather hose: just blew on it! Great taste, too.
Currently I’m leaning toward simply soaking most of the oil out of the “guilty” wells and calling those good for the time being.
Remove the PCV hoses and stick something like a screwdriver in the hose nipples to see if it comes out covered in sludge.
I have a parts washer that I dip stuff like this into to make sure it’s clean before installing.
Tester
1 Like
That is true but transformer dielectric oils depend on a few things to retain their dielectric properties. Exposure to atmospheric humidity will seriously compromise the insulating properties as well as acid (combustion gases) and entrained air bubbles. Dielectric oils are used in sealed environments. Arcing inside the case, when/if it occurs) creates carbon in the oil. However, if you have ever watched oil, or other liquid dielectrics, subjected to HV they are constantly flowing around in the enclosure due to the HV fields. So the carbon gets dispersed. Too much arcing over time and the oil becomes compromised.
The engine oil that seeps past the cover seals and into the wells has all three detrimental qualities so it’s not a great insulator at that point. A lot will depend on the creepage distance from the top of the oil to the terminal of the plug, if there is any silicone grease inside the terminal boot and so on. Personally, I wouldn’t let the condition persist too long and expect no negative ramifications…
We use a variety of dielectrics at work including both liquid and solid. Liquid dielectric oils need to be heated to remove moisture and degassed before and after filling to retain their full insulating properties. Units returned from the field need to have the oil exchanged and we refurbish it by complex filtering apparatus, heating and degassing it before storing for later use.
2 Likes
The amount of moisture that oil can absorb is pretty minimal. The oil that goes into distribution transformers is not degassed per say, but the transformer is filled in a vacuum chamber or is filled through a two way valve that allows drawing a vacuum first, then filling, somewhat like charging an AC system.
Oil circulates in a transformer from convection. Vent tubes are built into the coils so that oil can flow through them, up to the top and then down the sides for cooling. There is air or nitrogen gas above the oil level in the transformer.
Engine oil, especially if it has been in a vehicle for awhile will have some suspended metal in it. It will also have some carbon in it, not from arcing but from heat breakdown of the oil. But that is not enough to cause a problem for the spark plug.
Edit: personally I’d fix the seals because I don’t like oil leaks.
1 Like
The plug seal is an o-ring basically. Hard to screw it up. If your cover is not warped then plug well should be dry. But, it is not.
1 Like
It’s enough to reduce it’s dielectric withstand by 25% to 50% depending on conditions. We have dielectric oil testers and have verified the effects. Of course, the relative humidity in a particular location has a significant impact.
That is degassing. Using a vacuum to draw out the air. How much air becomes entrained just from the filling process depends on the method used. In some cases, for larger enclosures we use a dip tube to fill from the bottom and avoid too much agitation. While applying vacuum, the oil will froth as the entrained air is removed. Our systems require fairly tight clearances and creepage distances and still hold off up 750kV. So we pull low single digit torr values for extended periods to produce the highest quality oil possible.
As an example, new oil we receive from the manufacturer will routinely test at 30kV. After processing, it is capable of 45-50kV. If you leave it open to atmosphere, it will test at 15kV during the summer months.
That makes two of us!
Ok, I’m not reading through all the treads (edit: reply’s) but has anybody thought that the valve cover tube seals ONLY cover the top of the tube seals to the valve cover and not the top of the head tube seals to the cam cover??? Once you remove the valve cover, then you remove the cam cover (can bearing saddle) to be able to remove the cams that there is another set of seals, so basically you have upper and lower tube seals… If you keep replacing the upper and they are still leaking, and the valve cover is not warped/damaged then you might look into replacing the lower tube seals… Just a thought…
Also rather oil hurts the spark plug or not is not the problem, oil swells spark plug boots and COP (coil on plug) boots and that is damage that can/will cause misfire and other bad things…lol
What were you working on, transmission grid equipment? Distribution grid transformers typically test at 200kV. We also pulled <1 bar for a specified time about 2 hours. IIRC we did not heat the oil but the core coil assemblies were baked at 275F for 24 hours and the transformer was then assembled hot, which is tough on the assemblers. So the oil got heated from the residual heat of the core/coil assembly. The vacuum was not to degass the oil but to prevent air bubbles from forming as the oil was added. As soon as filling was complete, the vacuum was removed.
Never heard of this, only one set of seals.
Not something you will get in a valve cover set or probably even at your local parts house, probably either they are a type of Silicone gasket maker or a specialty engine parts supply store…
But if you look at the 1st picture I posted you can clearly see the cam bracket/caps missing and the seals at the top of the head for the spark plug holes…
Now look at the picture below and you can clearly see the cams installed and the break between the cam bracket/caps and the head… It is possible that is leaking…
Ugh no. The picture got cropped and cut that section off. But even then, I have worked on enough DOHC engines to know that that part has nothing to do with the spark plug holes.
The valve cover gasket does not go over the cam brackets. What you are missing in both pictures is the timing cover. A little silicone is used at the gap between the timing cover and the head so the valve cover gasket goes around the cam brackets. Oil flows through the cam brackets to lube to bushings.
That is funny that you have never seen lower tube seals… and you absolutely have NO idea of what I am talking about,
Here is a Nissan Sentra one… you can jump ahead to about the 4.30 minute mark…
Since some of the members don’t believe its not true if they don’t see it on YouTube,
Now I NEVER said that is the leak, only a possibility if they keep changing the VC W/tube seals and the VC is not warped or damaged… I only said again, it is possible…
So AGAIN for all you YOUTUBE guys here is what I was talking about… gezzzzz
Ugh No right back at you sir… that is funny, I guess this guy did it in the video also???..
I guess it is possible that all MY years working on vehicles doesn’t mean anything if YOU have never seen or heard of something…
Electron guns that produce high power streams of electrons.
Back to the practical, my Maxima had possibly the cheapest steel sparkplug tubes between the head and the valve cover that were easily bent/deformed when replacing the valve cover and then would leak oil into the sparkplug wells.
Try redoing the valve cover with new gaskets, being very careful to align the tube gaskets and if it persists, sealant is your solution.
Beancounter–thanks for the practical. When I replace valve cover gasket next time, I’m going to use a bit of extra gasket sealant around those well o-rings.
Oddly, I had a 97 Accord and I have replaced the upper seals. I never had a reason to pul the rocker shafts/cam cradle and the lower seals never leaked in the 220k miles I put on it. But we are not discussing a 97 Accord, or any Honda for that matter. My Son has a Sentra and my brother has a Versa. When my son first got his Sentra, which is an 06 Spec-V that comes with a HP Altima (2.5) motor and he wanted to put in NISMO cams. A neighbor cam over and inadvertently dropped a small retainer bolt into the timing chain cover.
The guy in your video is absolutely right about the amount of RTV in that engine. It is like a 6 layer cake with RTV frosting between the layers. I don’t know how your video guy did it but the 2.5 requires all five layers, including both oil pans to be removed in order to get the oil pump (Nissan name for the front timing cover because the oil pump is built into it) off. They use a lot of locating pins that require this level of disassembly.
You’ve seen the meme that says a 10 minute job is only one broken bolt from a three day ordeal, well in this case it was a dropped bolt that turned into a four day deal, three days of getting all the RTV off.
But back to the discussion, the cam cradle is RTVed in place so there are no seals under there and the OP had no reason to remove that so it is not very likely to leak. There is only one set of O-rings in the valve cover gasket, period. I have never seen either a DOHC or SOHC engine that had upper and lower seals in the valve cover.
@davesmopar I think one thing here is that we don’t speak the same language. I was focused on the valve cover and not the cam cradle. Also you used the term cam bracket which to me is something else. A cam bracket to me is the bracket located just behind the timing gear on older OHC engines. Those engines did not use cam cradles.
Since the engine had oil in the spark plug wells the first time the plugs were replaced, you could be right about the leak being under the cam cradle, it could be a factory defect and had been leaking since new. Usually if a seal is not disturbed, it doesn’t leak.
It is referred to as a camshaft bracket in the Nissan service manual. Other manufactures call it a camshaft cradle or camshaft carrier.
2 Likes
Thanks for the info. The first time I saw one, it must have been called a cradle. The rule of primacy, the first thing you are taught will stick with you, even if it is wrong. It takes ten times the effort to unlearn it.
1 Like