What the Spark Plug?

2001VolvoXC70 · Post by **2001VolvoXC70** » 11 Mar 2011, 02:01

So I just changed my spark plugs the other day. Oem ones in there didn't actually look too bad but they were gapped at .040. I thought this was a bit weird since everywhere says .028-.030. I gapped the new ones to .030 The car is running great and not so bad previously, I just felt I wasn't getting great gas mileage.

Something strange about the OEM spark plugs that were in the engine. When I took the 1st, 2nd and 5th out, they were rather difficult to remove, and a tad bit rusty on the threads. The others though were rather loose and easy to remove. Also, plug 3 and 4 especially had alot of oil on the thread of the plug.

: rusty threads and oily threads...click to enlarge

I was wondering if the oily plugs are a direct result of something weird happening from one of the cylinders or if it is more likely spillage from the oil filler cap?

endothrow · Post by **endothrow** » 11 Mar 2011, 10:36

I would say everything looks pretty good from a firing standpoint. The tips aren't too ashy, color is good and I don't see any oil on them that would give you reason to believe that you have bad combustion.

For the threaded sections, they don't see much action except incredibly high heat and expansion and contraction. It looks like you might have some heat wear on them, but nothing crazy.

Anybody notice anything that I am missing?

2001VolvoXC70 · Post by **2001VolvoXC70** » 15 Mar 2011, 02:52

thanks for the input. I was just a bit concerned about the oil I found on the the threads of 3 and 4. There was really a lot on the threads and around the socket area of the plug. If you enlarge the photo you can see a bit better. Where did it come from???

Also the rust on the other three, made it very difficult to get out. I turn to loosen, half a turn tight, a full turn loosen, half a turn tight and slowly I was able to get them out without stripping the threads on my head...Thank god. I wonder if there is supposed to be something to put on the threads when installing the plugs to eliminate this???

Post by **jblackburn** » 15 Mar 2011, 06:41

That oil came from the tops of the plugs rather than the engine side. That is usually caused by a bad oil cap seal. Check the top PCV hose to the top of the motor to make sure it's not spewing oil either.

Post by **jimmy57** » 15 Mar 2011, 08:54

Very much normal appearance of the threads. When you start the engine cold and it is really rich, some of the excess fuel wicks its way up threads and dries. IF the plugs are loose this is much worse and thread damage results. Worst case is the plug gets ejected (coil on plug would prevent outright ejection).
Anti-seize retards this but it doesn't wholly stop it.

2001VolvoXC70 · Post by **2001VolvoXC70** » 22 Mar 2011, 09:26

When I put the new plugs back in, I didn't use any anti-seize. I just screwed and since there was a (crush washer?) I cranked them a half turn once they were hand tight. Do you think it would be a smart idea to remove them and put some anti-seize on them then reinstall the plugs? also if I do this should I toss the washers on the plugs?

Post by **jimmy57** » 22 Mar 2011, 10:44

No, leave them in for 50K miles and don't worry. Sounds like you installed them properly. IF you ever remove them for any reason use anti-seize then. In any case you always used gaskets on flat seat plugs. Only the tapered seat versions go in with no seal.