I had some leaking valve covers about two months ago, and was warned this meant I'd need to have some vaguely defined extra service done during the next tune-up or I'd risk ruining the new spark plugs. I've decided to try replacing the plugs myself, which means figuring out what that service actually is.

So far as I've been able to figure out, leaky valve covers just let oil drip into the depressions around the spark plugs that I'll have to clean up. It seems you're supposed to thoroughly clean the surface of the engine around the plugs anyway though since you don't want any debris falling into the recently vacated holes, so I'm unsure if I'm missing something or the earlier warning was just redundant or an attempt charge me more.

Will I need to do anything special while replacing the spark plugs, in light of the fact that I've had leaky valve covers recently? Or is cleaning around the plugs before I take them out good enough?

If the specific vehicle makes a difference, I'll be working on an '04 Town and Country minivan with the 3.8L engine.

  • Welcome to Motor Vehicle Maintenance & Repair! Commented Jul 3, 2018 at 18:29
  • If the spark plug cavities have seals that are part of the valve cover then you need to clean out the spark plug cavities of oil before changing the spark plugs.
    – Moab
    Commented Jul 3, 2018 at 19:44
  • You probably won't need to clean anything. On the 3.8 the plugs are on the side of the head. Just blast it with some air and go at it. Don't forget to torque the new plugs.
    – Ben
    Commented Jul 3, 2018 at 21:32
  • @Ben: I think I'll clean it all the same just in case, there's a good layer of grime all around the visible plugs. I'll be sure to torque the new plugs too, having them fall out on the road sounds a little more exciting than I'd like.
    – Mirinth
    Commented Jul 3, 2018 at 23:23

1 Answer 1


Leaky valve covers won't ruin spark plugs, but yes - if oil is pooling around the base of a spark plug that is about to be removed, it could enter the cylinder and introduce contaminants that will shorten the life of the new spark plug and temporarily coat your oxygen sensors and catalytic converters with petroleum distilates enough to generate a code that illuminates your Malfunction Indicator Light on the dashboard. Do your best to extract any oil before spark plugs are removed.
As for the valve covers....use these two products: A tube of 3M Super weatherstrip adhesive and a can of Berryman B-12 chemtool.
When you remove the valve cover gasket, clean both surfaces (head and valve-cover)-and I mean Marine-Clean STERILIZE IT!! - with the Berryman B-12 chemtool by dabbing it on a paper towel and completely removing any oil or previous advehive. Take your time- patience pays on this step. Then apply a continuous coat of 3M Weather Strip Adhesive on both surfaces - Yes you will coat both sides of the gasket intentionally and glue it with a permanent seal....don't worry, it won't leak again and you'll have no need to remove a gasket again-(unless you have a major job requiring head removal - in that case - let a pro tackle the valve cover removal...it's not impossible) My factory valve covers usually leak around 60,000 miles and after sealing them with 3M, they never leaked for over 300,000 miles....and I am not exaggerating. The 3M weather strip adhesive will seal against synthetic oil....the most common cause of a valve cover leak.

  • I'll definitely get as much stuff off the engine around the spark plugs as I can before removing them. I already did the valve covers two months ago though, so I think I'll just leave them be until they act up again.
    – Mirinth
    Commented Jul 3, 2018 at 22:51

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