2003 Altima Spark Plug Tube - Factory Manual is Incorrect

[RemoGaggi]

I just helped a friend that has a 2003 Altima 2.5. A while back he was getting oil in the spark plug tubes. He took it to another mechanic friend that installed new tubes and a new valve cover as the spark plug seals on the valve cover were likely bad. I don't know why that mechanic friend thought to change the tubes also, but he did. They never could stop the oil from getting into the tubes and my friend asked me to take a look.

I looked and discovered that the spark plug tubes were not contacting the spark plug tube seal on the valve cover, leaving a gap for oil to splash through. I figured that the previous mechanic had set the tubes a little too low. I checked the factory manual and on page EM-66, it says the height is supposed to be 38.55mm - 38.65mm. When I removed the valve cover, I measured the tubes and they were at about 45mm - well over the factory spec, but still too short to make contact with the seal in the valve cover. Strange! If one was to follow the 38.55-38.65mm height spec for these tubes, you would have nearly a 1/4" gap from the top of the spark plug tube to the seal.

I installed new factory tubes with a height of 58mm. I did follow the factory manual for the bottom of the tube and applied sealant to the bottom 12mm of the tube and drove it into the head about that much. The new tubes now go through the seals on the valve cover and it solved the problem with the oil getting into the spark plug tube.

So, if you are replacing the spark plug tubes, don't just follow the factory spec, be sure to drive the tube in and make sure you have enough height to go through the seal on the valve cover.