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Spark Plugs And Oil In Cylinder, Help!


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#1
99Mazda626V6

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I was in the process of changing the spark plugs and noticed that one of the plugs wires had oil all over the bottom of it and on the inside where it connects to the plug. The specific cylinder is the one closest to the drivers seat, on the back of the engine that is closest to the firewall. I pulled the plug and it was soaked with oil also. I did not see anywhere where any oil could have leaked down from on top of the engine. I read another thread about the valve cover gasket being an issue sometimes, but this was just referring to the front of the engine correct? I did not see how any oil could have leaked down in the cylinder in the back. I am thinking maybe bad rings? I think the oil was a little past full also, could that cause this type of a problem? This 1999 Mazda 626 has 120k miles.

#2
audiqv8

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I did not see anywhere where any oil could have leaked down from on top of the engine. I read another thread about the valve cover gasket being an issue sometimes, but this was just referring to the front of the engine correct? I did not see how any oil could have leaked down in the cylinder in the back. I am thinking maybe bad rings? I think the oil was a little past full also, could that cause this type of a problem? This 1999 Mazda 626 has 120k miles.


There is also a VC on the back of the engine. This is a V6 and there are two VC gaskets one for the front and one for the back. The back is a little more time consuming to change because you also have to remove the IM (intake manifold) inorder to get to the rear VC gasket.

#3
99Mazda626V6

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So this probably is the valve cover gasket instead of the bad rings or another issue, would everyone agree? After all, there was oil on the bottom of the plug wire. Besides removing the Intake Manifold, is there anything I should know about before I attempt to replace the valve cover gaskets? How long might it take?

#4
NickR

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audiqv8 is definitely right. It is the leaking VCG which causes this problem. Part of the VCG is a ring gasket about half way up the spark plug wells. When it leaks, oil drips down into the spark plug wells, saturating the spark plug wire and the spark plug. Bad piston rings can leave oil (or burnt oil) on the tips of the spark plugs, but not on the spark plug wires.

Here is a long thread on changing front and rear VCGs. http://www.mazda626....showtopic=12906 Check your front bank spark plugs first, because changing the front VCG is easier, and so it is good practice to build up confidence before tackling the rear VCG. And when you change the rear VCG, do the hardest bit first: locate and remove those two accursed bitch bolts!

#5
JS626LX

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Valve Cover Gaskets it is. Replace both at the same time so you don't have to go back and change the other sometime in the near future.

#6
audiqv8

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So this probably is the valve cover gasket instead of the bad rings or another issue, would everyone agree? After all, there was oil on the bottom of the plug wire. Besides removing the Intake Manifold, is there anything I should know about before I attempt to replace the valve cover gaskets? How long might it take?


Since you will be removing the intake manifold, there is a rubber coolant hose which you should also replace while in there. It is highly recommended to change this hose or at least inspect the hose each time the intake manifold is removed.

#7
NickR

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I don't remember that hose. I remember there being two (I think) metal coolant hoses running along the V, underneath the IM. Maybe they have rubber end connections? Do they (or the rubber bit) normally need replacing? I didn't replace mine. I remember reading about one case (either here, MX6.com, or on ProbeTalk) where one of those hoses was leaking, and needed to be replaced. But I don't think it's a common problem (correct me if I am wrong). I agree though, it would be a good idea to inspect those hoses while you have the IM removed, because it would be a PITA to have to remove the IM again later.

#8
audiqv8

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I don't remember that hose. I remember there being two (I think) metal coolant hoses running along the V, underneath the IM. Maybe they have rubber end connections? Do they (or the rubber bit) normally need replacing?


NickR you are correct about the metal coolant lines located at the bottom of the 'V' The metal coolant line, also known as water bypass line is attached to a rubber hose on the left side (driverside), this is the hose that I am refering to, it is so much easier to replace or at least check the hose with the IM off. Don't really want to remove the IM again to replace this hose.

#9
99Mazda626V6

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Thanks for the replies, I understand what is going on now. Any suggestions on where to purchase the
valve cover gaskets or a good brand?

#10
NATE06

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I have alo been troubled by this problem. i just wasnt happy with the vcg idewa so i took the head and everything off. i just got the new gaskets for it and hope to have it assembled this weekend. hope fully everything will be ok but i hear that the pvc valve could be the problem so i will also replace it too. i will let you know if i have any luck.




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