Driving home from vacation last weekend and I hear something blow, and this real loud popping sound is coming from under the hood. I pulled over right away and opened the hood, and one of my spark plugs had apparently been working its way loose for the past few weeks (I changed my plugs almost 40k miles ago myself when I was in Florida). When I tried to screw it back in, it just kept turning, like real loose, even my hand could turn it. Of course I started it up and it blew right out again. With an aluminum head, which all cars have now apparently, theres no way to easily rethread or put an oversize plug into the hole. You basically have two options: You can buy a heli coil or Time Sert to put new threads into the hole without disassembling the engine. You run the risk of having metal chips fall into the cylinder which of course can score the wall and require me to disassemble the ENTIRE engine and get it machined and put new rings in. Even though there are several methods for getting the junk out of the cylinder, including filling it with oil and vacuuming it out, and running the engine with no plug in to blow everything out – your still running the risk. It could also just not work right, and I end up having to remove the cylinder head anyways, and sending it to a machine shop, which would cost me about $900. It pretty much completely sucks either way. I don’t know how the thing got stripped in the first place, I guess I overtightened it when I was installing down in Pensacola the new plugs?? Ive done many plugs before, and I was super careful not to over tighten these, I don’t know how it happened?? I’m never putting new plugs in again, unless I have a torque wrench and plenty of room under the hood to work. I've read that this is a common problem with certian Ford engines because they only put like 3-4 threads on the plug - if this doesnt sound like poor engineering I dont know what does. Anyways, I’ve decided to have the guy give a go at installing the time sert without taking off the head. I really don’t know what else to do, he tells me theres an 80% chance itll work fine, I guess I’ve got to give it a shot. I was lucky that I found a shop that will even attempt it, they told me that a few times when they’ve done them in the past without taking the head off, they’ve ended up buying a new engine, or it ends up with an oil leak, all of which sucks. Id like to hear about any experiences you guys have had with this problem, and am I crazy for trying to have a time cert put in without removing the head???

 

Personally, I'd pull the head. And not so much to install the Heli-coil but to inspect the current condition of the cylinder. Where the threads used to be was a bunch of metal. It went somewhere. Either in or out the motor.

Now since you have aluminum heads, chances are nothing hapopened. Aluminum is a lot softer than a cast iron block or steel piston rings. Your piston couldn't care less if a few metal chips got in there. Likely anything that got in the cylider blew right out the exhaust.

So the repair with head installed is simple if you use a drill and tap with grease on them. The grease will trap all the metal shavings. Trick is easy access to the spark plug hole in question.

 

Thanks for the reply. I know that as soon as the plug was blown clear of the hole, it was at least a few minutes before I could safely pull over ( I was on the chesapeake bay bridge!) so anything that was in there like you said shoudl hope fully have blown out the open hole or the exhaust. Like you said, the main reason Im going to try repairing this with the head on is the aluminum is soft enough that I think theres a good chance small shavings wouldnt cause a major problem. I also dont have the tools or expertise to pull the head on this vehicle. I'm more of an ameteur who knows a lot of theory but I havent done a lot of work personally on engines. I read the board a lot, but I just rarely post - which is kind of strange, I'm listed as a new user, but I've been on the board for years, the rating must just be based on number of posts.

 

If you take a look in the 4.6/5.4 and 97-03 F-150 forums you'll find quite a few posts about this and how they were repaired.

 

Yeah Racerguy, I read all of those posts to the very end. I just hadnt heard anyone mention how risky doing the time sert is or which method is preferable if your someone who is paying for the work.

 

If I was paying I'd do the insert.
I've seen quite a few of them repaired that way with no problems.

 

Thanks, I appreciate the input. I'm going to go give that a shot today.

 

I got my explorer back on friday of last week. The new plug was installed using a t-sert, they reused the old coil. It seemed to run fine on saturday and for work yesterday, however today on my way to work I noticed a slight shuddering while accelerating. It almost seemed like it was a bad U-joint, but I also noticed it at low speeds, so I dont think thats the case. My hope is that it may be a bad coil on that plug that blew and its causing an intermittent misfire - does that seem like thats what could be causing this symptom? I didnt notice a lack of power, and I didnt notice any trouble shifting or slippage in the transmission at all. Does anyone have any ideas what might be causing this? I know that it was not doing any shuddering before I blew the spark plug, so the chances of it being unrelated would be bizarre. However, anything is possible. Im really baffled by this, Id appreciate any input.

 

Replaced the coil on the blown plug - problem solved.