Hey everyone,

This evening I was changing the plugs on my new to me Excursion. The driver's side bank went well with no difficulties, and all was well on the passenger side bank until I got to cylinder #4. I pull it out and find oil all over the plug...

I'm thinking either valve seals or a bad cylinder. Truck runs and drives just great, but at the same time I'm not sure I would notice a single misfire with nine working great.



What do you guys think?

 

Now this is confusing...got to the number five cylinder and saw the same thing. But I also noticed on each plug that the oil goes above the threads...where could it be coming from?

Here's the number five plug:

 

Few of mine looked something like that when I changed plugs. Still running good many miles later. I have seen it from a few other v10's also.

 

Any signs of oil in the plug recess in the head? Given the amount of oil on the plug I expect the tip of the plug to be much darker if it was burning oil. Also the oil comes up high on the plug and even looks to have stained the ceramic that the boot did not cover. The COP boots do seal off the recess fairly well but dirt and liguids can still get past.

The #4 and #5 cylinders are close to the PCV valve and hose, any chance of crack in the hose or leak? See any leakage at the valve cover? Even on my 04' with the upgraded PCV hose I notice some oil mist on the valve cover. I just think if the oil was coming into the cylinder from a bad ring seal or valve seal signs of oil would be below the taper and the ground bar covered with burned oily deposits. Were the plugs tight when you removed them?

 

How close to the oil filler neck are those plugs?

 

Hi Chris. Not very, these are the two cylinders closest to the firewall on the passenger side of the engine. The oil filler neck is near the front of the engine, and there are three cylinders between that and the number four. ON edit: Someone on another thread suggested that the valve cover gaskets may be leaking, which makes sense considering the two cylinders are right next to each other.

 

Hmm, wouldn't a valve cover leak drain down towards the exhaust manifolds?

 

This outta take care of it.

Ford Excursion/F250 V10 6.8 whipple 2.3 supercharger | eBay

 

The top side of the valve covers are right up against the recess for the COP/Plugs.