295k on my 1998 runner and on my way to work this morning experienced a loud pop, pop, pop coming from the engine, limped it off the road about 1000' to a parking lot and discovered oil coming from the top of the valve cover on the right side. had it towed home and started investigating, the middle coil pack boot was completely melted away and I fished the spark plug out which was just sitting in the sleeve and it was in rough shape with no terminal nut left on it. not sure the root cause of this but either I picked up a new coil pack and plug set (to replace all while i'm in there) and got the new plug to turn about 1/4 of the way in and stopped, I don't want to torque it anymore as it seems damage to the threads on the head has been done. what are my options (cheap) to get the plug back in? I don't want to remove the head if I don't have to but if it's the best thing to do then will.. I am not super technical but am willing to learn and have tools.
blew a sparkplug, new one won't seat
- Thread starter snowninja
- Start date
Register to hide this ad
KidVermicious
New member
Your first move should be to get a tap the same size as your spark plug and chase the threads. Use LOTS of grease and go very slow so you don't drop any shavings into the cylinder.
But it's probably not going to work. If the spark plug literally blew out of the cylinder head, then I doubt there's enough material left to rebuild the threads, and even if you get the plug to thread it'll still leak compression or just blow out again. I think you're in for pulling the head, and at your mileage, it might be worth yanking the entire block and rebuilding it.
But it's probably not going to work. If the spark plug literally blew out of the cylinder head, then I doubt there's enough material left to rebuild the threads, and even if you get the plug to thread it'll still leak compression or just blow out again. I think you're in for pulling the head, and at your mileage, it might be worth yanking the entire block and rebuilding it.
EatonKyleH
New member
You could always have a Time-Sert installed. Its a good fix if done right. Heck its a TSB repair on some newer Ford models that blow the plugs out on a regular basis lol.
Anyway look it up if you like and I'd recommend having a shop familiar with the process do it. Its pretty inexpensive and would be the best repair short of pulling the heads.
Anyway look it up if you like and I'd recommend having a shop familiar with the process do it. Its pretty inexpensive and would be the best repair short of pulling the heads.
I just recently had an issue with one of my plugs seating into the threads properly. I think the last guy to change the plugs either didn't use a release lube and/or tightened it down with a wrench rather than hand tightening them. So when I took #6 plug out (the hardest one), it partially stripped the threads.My friend is a GM at a mechanics shop and had one of his guys who came from a Japanese specific shop rethread the plug cylinder. That was about a month or two ago and so far no problems.
He might have done exactly what KidV said, but I honestly don't know. All I know is that it worked and I have had it pop out since. I also have ~100k less than you, so pulling the head is definitely an option to consider. Pulling the head also gives you some performance options (milling the head as one example).
He might have done exactly what KidV said, but I honestly don't know. All I know is that it worked and I have had it pop out since. I also have ~100k less than you, so pulling the head is definitely an option to consider. Pulling the head also gives you some performance options (milling the head as one example).
here are a couple of pics showing the blown out plug next to another that I took out to compare as well as a brand new. the blown out one has obvious damage on the bottom threads and after the first 2 or 3 they look ok aside from the edge being a bit flatter. i can get a new plug in about 1/4 of the way before it stops so that tells me the first few threads are fine but below they are worn. based on this does it look like a tap might correct rebuild the threads without having to do a helicoil or timesert? not sure
also there is a pic of the damaged parts, the coil was cracked at the mounting tab due to the pressure of the plug hitting it i guess.
also there is a pic of the damaged parts, the coil was cracked at the mounting tab due to the pressure of the plug hitting it i guess.
Attachments
Swimmerboy2112
New member
As a former Ford mechanic this was a fairly common occurrence.
As was mentioned earlier, I'd try and tap out the threads SLOWLY and use ALOT of grease (we used red bearing grease) to prevent shavings from falling into the cylinder. That plug doesn't look too bad so I have faith that it will work.
As was mentioned earlier, I'd try and tap out the threads SLOWLY and use ALOT of grease (we used red bearing grease) to prevent shavings from falling into the cylinder. That plug doesn't look too bad so I have faith that it will work.
KidVermicious
New member
Looking at that plug, I'd guess you're correct that it wasn't torqued right and just backed out over time, until the last one or two threads let go. Maybe I was too pessimistic - chase the threads real good, and see if you can get a new plug to torque. You might have gotten lucky here.
ok sounds good, thanks! is there a particular chaser that is better than others? most i see are kinda short and not sure how well they would hold in plug socket when trying to pull out. i found this on amazon and it looks like it's long and would be easier to pull out Amazon.com: Powerbuilt 640811 14mm Back-Tap Thread Repair Tool: Automotive
any recommendations?
any recommendations?
I went ahead and ordered that one but was in town today so stopped by autozone and they had a 14mm spark plug thread chaser for $8 so I bought it. I tried it but noticed that it turns in really easily which was unexpected. it also feels loose, I put it in another plug hole and could only get a turn or two before it tightened up. I also noticed what looks like a ring at the bottom of the hole on the damaged hole which and the "ring" is slightly smaller then the rest of the hole. the good one doesn't have this. I am kinda at a loss here for what is going on. it doesn't appear there was any modification done to it (helicoil for example) just not getting why the chaser is so loose and the new plug still get's stuck 1/4 of the way in. I spec'd the chaser with my digital caliper and it measured 14mm so it is the right size.. I guess i'll wait until I get the one from amazon and see what happens.
I am going to try the backtap but if that doesn't work will put in a timesert. With all the shavings possibly dropping into the cylinder I plan to blow them out with an air compressor. What is the best way to make sure the exhaust valves are open? My understanding is they open on the second sroke of the cycle but want to make sure I have it right.
KidVermicious
New member
I consider myself pretty handy in the garage, and I would not try to do this on the truck. I have had to helicoil a pair of exhaust studs on my current motor, and I did both on the truck. Even taking the utmost care I wasn't able to get either exactly straight, and those are at exactly 90* to the block with great access in the engine bay, neither of which is the case for you. There's just a certain amount of error you have to factor in when you're freehanding with a drill, and doing it under the hood magnifies that error factor.
I know it's a PITA, but I would pull the head and do it on your bench where you have the best control of what you're doing. Even better, pull the head and take it to a machine shop that has the experience and precision machinery to do it right. I think if you do it on the truck you're asking for trouble, and trouble in this case means a new head. I wouldn't risk it.
given so many miles and no problems to date I decided to save myself the time and money of removing the head and went forward with rethreading the sparkplug with a sav-a-thread. I was super careful with making sure it was straight, went slow, and used a lot of grease to catch the shavings. what I wasn't able to catch I used a shopvac with a flexible straw on the end so I could get into the hole and run it around the outside of the cylinder and wall. it picked up a few shavings and after a few minutes of spinning it around was pretty confident anything that fell down was now in the shopvac canister. I also changed out all the plugs and checked hoses, etc. one thing to note my valve cover gaskets were replaced last year and decided to check the bolts, many of them were 1/4 to 1/2 turn loose. I decided to tighten them so they were snug but didn't want to squish the rubber grommet too much so hopefully no issues come from that.
anyway I am back on the road and after 35 mile commute all looks good.
i'll follow up in a few months on this thread and let you know how it's going.
one question I do have - I used antisieze on the plugs and but didn't have a torque wrench so what is the spec for the plugs? i did hand tight with about a 1/2 - 3/4 turn with the socket
thanks to all the replys on this and for helping me get my love back on the road!
anyway I am back on the road and after 35 mile commute all looks good.
i'll follow up in a few months on this thread and let you know how it's going.
one question I do have - I used antisieze on the plugs and but didn't have a torque wrench so what is the spec for the plugs? i did hand tight with about a 1/2 - 3/4 turn with the socket
thanks to all the replys on this and for helping me get my love back on the road!
kball
New member
It's around 15-18ft lbs. As you can see in your own picture comparing the new plugs to the old there's a crush washer on the plugs. Once that washer is crushed you're done. You will feel the plugs stop then when you add torque they will spin a little more and stop again. That's the crushed spot. If you are using a torque wrench set at the right specs it would be clicking at that point.
I pulled my coil pack today to see how the repair was looking and what do I find? Oil all around the top of the coil pack boot and a puddle of oil in the bottom of the spark plug tube. My guess is the oil had been leaking dripping into the tube and over time enough oil worked it's way down into the threads of the plug and it backed out and finally blew. this would also explain the blue smoke (burning oil) that billowed out shortly after the plug blew out. At this point it seems either a faulty install or the shop didn't replace the old O-rings.
I'll be calling tomorrow to let them now and see how we go about getting this fixed. I'm half thinking of doing it myself so I know it's done right this time.
I'll be calling tomorrow to let them now and see how we go about getting this fixed. I'm half thinking of doing it myself so I know it's done right this time.
