These are out of my 2006 F-150 4.6l with 75,000 miles. Can someone tell me what the heck is going on with plugs 5 & 6 and what I need to do to fix it?

 

Looks like you have a coolant and/or oil leak around those 2 wells.

 

#5 appears to have been installed with some kind of anti-seize.

Both #5 & #6 appear to have burnt-on oil or coolant on the outside, probably from either some external leak or from sloppy maintenance.

Edit: Dang, need to type faster.

 

Well the vehicle is ten years old and I am just now getting around to changing the plugs, so im guilty as charged as far as sloppy maintenance goes.

Moving forward, what type of maintenance can I do to keep oil or coolant out of the well?

These are the original plugs, I am the original owner of the vehicle so I know for certain. Do you think Ford would have put anti-seize on only one plug?

 

How many miles has that engine got on it? The plugs look WELL used. The gaps look too wide and the center electrode doesn't have sharp corners that it needs to have any more. I wouldn't be surprised to hear that you had some misfires. I'd need to too see the end of the plugs and down into the gap between the center electrode and outer shell to say more.

I would be worried about that heavy coating on the threads of the #5 plug. The heavy coating on the outside of the plug body is indicates that something has been leaking unto them but even then there shouldn't be anything getting down into the threads! I don't know what that coating is but it doesn't look like engine oil so I would trying to find out what it is and where it came from.

PS clean out the spark plug wells WELL before putting in new plugs, especially that 5 and 6. Any crud in there could prevent the plugs from seating properly and could lead to a blown plug, stripped threads or valve or piston damage if it falls into the cylinder.

 

And torque the plugs to 28 ft/lb, don't use anything but Motorcraft and don't use antiseize.

Joe, he said 75k. That's not sloppy maintenance.

 

I used Motorcraft SP-493 plugs, torqued to 20 ft/lb with a calibrated torque wrench, no anti seize. The 2006 4.6l trucks are 2-valve and don't have the spark plug blow-out problem so I didn't want to go more than 50% higher than the stock torque spec.

 

I have heard of the 8 thread heads blowing out plugs.

 

I'm not surprised considering that some of my plugs were surprisingly lose, the stock torque spec is definitely inadequate.

 

I missed the part about 75,000 miles. But I NEVER said anything about sloppy maintenance. If you're trying to infer 75,000 miles is adequate change interval I would say to compare the gap on those plugs to what the factory calls for and then look at the worn condition of the electrodes and tell me if you think that using plugs in that condition is really acceptable. The gunk on the threads of that one plug is certainly not acceptable.

 

Same here, especially if they're loose enough to allow that much crud to get down into the threads. From the looks of the depth of that crud on #5 it doesn't look like there's much thread left on that cylinder head! I also noticed that the top of the some of the threads on that plug are beat up. I HOPE it something that happened after the OP took them out. If they were in the head like that then they're bound to have added a lot of wear on the hole threads.

I know the OP said that those are factory plugs but #5 looks to me like the plug was too loose in the hole and someone used some of that old style hardening pipe dope on it. I don't know else looks like that OR how else to explain why it's on the threads or why there's isn't more of a thread impression from the threads in the spark plug hole.

 

Here are some close up pics. The spark plug is exactly as it was removed from the cylinder head, again the factory spark plug, never touched. I have owned this vehicle since it had 6 miles on it.

Here is my theory after considering everyone's input. The plug was not torqued down sufficiently from the factory and it looks like the factory threads in the cylinder head have more clearance than the others (manufacturing defect?). This allowed oil/coolant to seep down past the seal of the plug and all they way into the cylinder. You can see how the oil/coolant is making its way down the threads eventually turning into the charred white color (from heat?). The end of the threads on the plug aren't damaged (I don't think), I believe that portion of the plug is hanging out of the cylinder head in the combustion chamber and that's why the "gunk" filled in those threads, I don't know why threads of the cylinder head didn't clear them out upon removal, I suppose this is further evidence the threads in the head were poorly machined...

The vehicle has 75,000 miles on it. The change interval in my manual states 100,000 miles. But since the truck is 10-yrs old now I figured it was time to do it anyway, I sorta thought I was being pro-active...

So what is the fix, if one exists?






I wiped the seal clean on the following pics to see if there was any evidence marks indicating where the oil made it past.

 

If the #5 plug wasn't tight, then the stuff on the threads is probably residue from whatever seeped down into the wells and got cooked. Still looks like anti-seize to me, though...

I'd just clean out the holes, install a new set of MC plugs torqued to 28 lb-ft and quit obsessing about it for now. Check back in there in a few months to see if there's any evidence of coolant or oil leakage into the plug well and then, if needed, take appropriate measures.

 

Exactly what I would do.

 

My guess would be that the engine had a wet weather miss while at the dealership. The 2 plugs were pulled and somebody took a wad of di-electric grease and reinstalled the plugs only missed torquing down #5. The guys name was probably 5 o'clock Charlie and it was late in the day. As I recall, the plugs are installed in the heads by machine from the factory and there's little chance of one being loose. If the engine is running right as of now, I don't see a fix needed.