Oil on spark plug threads - Left bank only

[Rick]

I just changed the plugs in the Pumpkin today. After thinking about it this morning, I couldn't remember when I last changed them... By the looks of what I pulled out they were way over due!

All of the plugs on the drivers side were wet with oil around the threads. Nothing seeping from above. There was quite a bit of build up on the left bank plugs too.

The plugs on the right side had dry threads, and very little if any build up on the electrode and insulator

Bad intake manifold gasket? Sucking oil into the ports? That's the only thing that I can think of. I've never heard of rings or valve seals going bad on one bank, but not the other.

 

[IAmTodd]

My first thought was lower intake as well. Can't hurt to try to torque them down to see if they're loose as a first step.

 

[Anime]

Does the motor still have the stock intake gaskets on there? The design Ford used wasn't the best, a newer metal&rubber lower intake gasket seals much, much better.

I'd agree it's likely the gasket in this case, if it was just one cylinder maybe it could be rings or seals, but probably not on an entire side.

I'd think it could also be a cracked head or blown head gasket, if the head is cracked between the cylinders or the gasket is blown in several places, but that seems unlikely unless the engine overheated.

Not a bad idea to change the upper and lower intake gaskets anyway, especially if they're that old. Hopefully you'll be able to tell if there was some oil leakage there just by looking.

 

[malohnes]

I have had issues with loose LIB bolts too, but if the original gaskets haven't been changed, I doubt it is loose bolts even if they are loose. Fresh gaskets is a good idea, so my suggestion would be to check the bolts and if not difference, then go for fresh gaskets.

 

[Rick]

Not the stock intake gasket set. I installed rebuilt heads 8 or 9 years ago and used FelPro gaskets. Torqued everything to spec and made sure everything was clean.

I'll dig in there and torque the manifold just to be sure it didn't loosen up.

 

[Anime]

Which FelPro gasket set though? They make a cardboard set that's about the same as the original factory set, and a version of the newer metal/rubber set, although still not the same as the metal/rubber one from Ford or Dana/Victor Reinz.

Since the driver's side plugs are easier to get to than the passenger side, you could always just re-torque the intake bolts, then check a plug or two again after a few runs and check for oil again.

Hopefully it's not a head issue, but rebuilt OE heads aren't any better than old OE heads, though if they were 93TM instead of 90TM they might be slightly less prone to cracks. If you do find any possibility of a head issue, new aftermarket heads are definitely the way to go.

 

[Rick]

I installed the metal FelPro gaskets.

 

[boominXplorer]

Stuck open PCV valve maybe?

 

[Anime]

If it was excessive oil getting in through the PCV valve, it'd probably be just in the rear cylinders, not just the left side. The intake manifold is constructed such that oil coming in from the PCV vent would leak into the rear and perhaps the middle tube of the intake, but those go to the rear two and middle two cylinders on each side.