I purchased my 2004 Explorer 4.6l about three years ago. I did a basic tune-up including air filter, oil change, and I checked the spark plugs. The plugs looked great so I put them back in. I noticed a small amount of coolant in the #6 and #7 spark plug bores, on the cop boots. I thought that since there was no coolant in the oil, and no oil in the coolant that this was a fluke and might be ignored.

Fast forward to today. I have a misfire in cylinder #6 that causes a service engine soon light to go off. I stop at a parts supplier and get some new plugs, go home, and begin to change them out. I get to #6 and it is filled with coolant so high that the socket splashes the juice all over the valve cover. Number seven has some in it too.

My question is regarding coolant passages and the possibility of a cracked head. Is there any other reasonable cause for the coolant in these bores? Has anyone else had this problem? If it is cracked and leaking, what heads can I use to replace it with?

 

i dont know about the 02-05 explorer but the expeditions had a issue with a small coolant hose running over the motor on the firewall basically and they would develop a leak right above and cause exactly what you described. i'd check for coolant leaks everywhere before i worried about a cracked intake or block..ect.

 

The problem I have with that is that there was no coolant on top of the cop boot. Only in the bores. It took three years for it to fill up, and 15,000 miles of driving. I just don't see how a cracked head could be so slow to leak. I also can't see how it is getting in there without wetting the top of the boot.

 

well the fact its not puddled means it could dry faster then what went down in the plug hole. i'm just thinking you have a much more minor issue at hand. i'm keeping my fingers crossed for you! look it over very well for any coolant hoses that run anywhere near those COP's

 

All the coolant lines run on the other side of the motor and go into the firewall. The only other line is the top radiator hose, and that one would be a big time leak. This thing is dry on top with only dust to show for its travels. I am keeping my fingers crossed as well, but I fear the reaper a little too much right now. This is MURPHY PRIME TIME....

 

Are you absolutely positive it is coolant and not just contaminated water? The Lincoln LS had a problem with water from the cowling at the base of the windshield guiding water under the cover for the coils, allowing water to puddle in the plug wells and causing misfires. The coil boots would often have an orange look swirled look to them, I suppose from the contaminants in the water being deposited as the water evaporated. Some folks interpreted this orange appearance as coolant (even though the cars had green coolant in the cooling system).

-Rod

 

If it is a leak, it would be more likely due to some porosity in the casting than a crack since it's such a small amount. One you rule everything else out, try the GM coolant stop leak pellets. They actually work very well and have been proven to not plug the radiator like aftermarket liquid stop leaks can.

 

I am ABSOLUTELY SURE IT IS COOLANT. I am 43 years old for Christ's sake. I know the difference....

All kidding aside, after a plug change last night, the truck threw another curve ball tonight on the way home. On the freeway after about twenty miles of driving it started misfiring again. The "service engine soon" light started flashing again and it was losing power. It was shifting down to climb a weak grade at fifty miles an hour. I honestly thought the truck was taking a death roll. And then it just stopped. The misfire subsided, and the thing drove perfect. I get home and the codes read #6 misfire again. I pulled the cop and it was dry as a bone. So was #7.

Can the coils fry out if they are short circuiting for long enough due to water in the mix? Where do I go from here? I guess replacing the coils would not be a bad idea. But this looks like the old "throw money at it" tactic. I think this is going somewhere bad.

 

Porosity in the casting sounds a lot better than a cracked head any day. I am leaning toward this theory as the bore was dry today after 60 miles of driving.

GM oil in my supercharger in the Mustang, and GM stop leak pellets in the cooling system of the Explorer. Can't Ford make this ****? I am sick of going to Chevy dealerships for solutions to issues... I have only owned Fords, nothing else.

 

Thanks for the somewhat limited interest in this thread, and the suggestions as to the problem. In the end I found the culprit to be the coils, but only in part. I was informed that the boots are replaceable by themselves. I bought two of them and the problem was solved. They were $4.99 each at Autozone. All told I spent around $50 total. I still have to figure out the leakage issue. I will pull the coils every three
months to see if there is moisture.

 

Thank you for the follow up post on what you've found so far. Please keep the thread updated as you learn more about the source of the leak.

-Rod

 

The plastic intake underneath the aluminum coolant crossover has prob cracked and dislodged the gasket. Take the thermostat out and inspect the intake. Look for a rubber gasket sticking out under the thermostat. Only fix is to replace the intake.