97 4.0 SOHC - Spark Plug Replacement | Ford Explorer Forums - Serious Explorations

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97 4.0 SOHC - Spark Plug Replacement

ctgriffi

Member
Joined
February 2, 2017
Messages
32
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3
City, State
Springfield, MO
Year, Model & Trim Level
1997 Explorer XLT
I just bought this 97 XLT a few months back, and it's in amazing shape for the age—just about everything works, and the body is rust-free! I don't know the maintenance history, other than it's had a lot of dealership work, but I figured it's always a good idea to do plugs/wires, like I've done on all my vehicles for many years. Well, not so fast...

I started pulling the Motorcraft plugs and they were pretty tough to get out; took a lot more force than I expected, given that they're supposed to be torqued to just 20ft/lbs. After pulling just two of them, I stopped and tried installing a new plug, threading it in slowly by hand, but it just doesn't feel right to me. The plug will go in like half a turn and then stop, despite me backing it out and trying all kinds of angles, etc. I do not want to just wrench it in there because I'm worried that will destroy the threads, obviously.

Any ideas? Is this typical on a 20 year-old Ford? What would you do? (Btw, on the two plugs that I removed, gap is way below the spec of .054".) Appreciate the help!
 



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You probably got carbon in the threads. There's a tool to clean/chase spark plug threads. You should be able to find one at most auto parts stores. It's a bit like a tap, but not so aggressive.

Also, putting a dab of anti-seize on the new spark plug's threads might help.
 






You probably got carbon in the threads. There's a tool to clean/chase spark plug threads. You should be able to find one at most auto parts stores. It's a bit like a tap, but not so aggressive.

Also, putting a dab of anti-seize on the new spark plug's threads might help.

Thanks, koda. Hope it's something pretty simple like that. Also, here's a photo of one of the holes, if that helps further the diagnosis...

GgZNSRxTBrY5BDf-vHlmjI5Hk60hM3xkEpcP=w1099-h917-no.jpg
 






You have Motorcraft replacement plugs, correct?
 






You have Motorcraft replacement plugs, correct?

Actually, no. The new set I bought are NGK G-Power 3403—heard they were pretty good plugs. Why do you ask?
 






Actually, no. The new set I bought are NGK G-Power 3403—heard they were pretty good plugs. Why do you ask?

Most here use/recommend Motorcraft or Autolite spark plugs. I've always had good experiences with NKG plugs though. Fords are fussy about spark plugs and the don't do well with Bosch plugs for some reason. NKG's will probably be fine. In the brief time your photo was visible I'm not sure if I could actually see threads in your spark plug hole. How did the spark plug that came out of that hole feel coming out and look? Did the threads come out with the plug? That can happen if you don't use anti-seize on steel plugs in aluminum heads due to dissimilar metals electrolysis. If this is the case all is not lost. There's a thread repair system/tool called a Helicoil.
 






In the brief time your photo was visible I'm not sure if I could actually see threads in your spark plug hole. How did the spark plug that came out of that hole feel coming out and look? Did the threads come out with the plug?

Appreciate the help! So, neither of the two plugs felt good coming out; it took some pretty hefty torque to break 'em free and then they were still slow-going. I did a lot of the loosen-tighten-loosen-tighten method, to avoid breaking anything off in the head. And no, I didn't see any thread material come out with the plugs. Here's a photo of one of the original plugs:

0zjmqcsTlOMSQLQh83ulXUMHjwy4A86819UqckqoBkVQNcCYCMVTuMTcDBL9Tx9PGqq21h2Qjg=w328-h317-no


(Btw, is there a better way to handle images on this forum? I couldn't find an option to upload anywhere, so I just posted a link to my photo on Google Photos.)
 






You are doing great with the photos.
 






Photos - Unless your have an Elite Explorer membership you can't post pic's directly. You need to use something like PhotoBucket or Google Photo.

The treads on that plug look okay, but it doesn't look like it had any anti-seize used on it. That black stuff on the threads is probably carbon. Use a thread chaser on the head and then use anti-seize on the spark plug. Then the plug should go in pretty easily.
 






I hope you're right, Koda. Were you able to get a good look at that first photo I posted? You can just barely see the threads down in that hole if you zoom in... they don't look good to me, but it's hard to tell. :(
 






I hope you're right, Koda. Were you able to get a good look at that first photo I posted? You can just barely see the threads down in that hole if you zoom in... they don't look good to me, but it's hard to tell. :(

I agree, they threads don't look very good in that photo. If worst comes to worst you can always use the Helicoil spark plug thread repair kit. Helicoils work really well. I've used them for years to repair threads in aluminum. They're much stronger than the original threads. The kit comes with a drill bit, the Helicoil insert (which looks kinda like a stainless steel spring) and the installation tool.
 






Gotcha, well I'll see what I can do with a thread chaser (ordered the Lisle 20200) and go from there. Appreciate the advice.
 






Gotcha, well I'll see what I can do with a thread chaser (ordered the Lisle 20200) and go from there. Appreciate the advice.

Good luck. Let us know how things turn out.
 






Things haven't turned out well. I've spent hours trying to get those two plug holes cleaned up. I don't know if those plugs were in there for like 20 years, or if the last set was just installed really poorly, but those threads are a disaster. I've never spent this kind of time on a plugs/wires job.

I used the Lisle thread chaser over and over on the #5 hole (slowly in and out, in and out, like I was using a tap, which I wish I had now). I used heavy grease on the end of the chaser and cleaned it up with every pass 'cause there were lots of metal chips. Finally, I got that hole to the place where the new plug would thread—still felt rough going in, but I think it's in there pretty good.

The other hole, #4, has been even worse, and it's harder to access because the power steering fluid reservoir and the AC compressor are right next to it. I can't get the thread chaser going at all on #4; it spins around and won't ever catch on anything. I just took this photo of the #4 hole, and you can see that the first few threads are gone, but there are several good threads further down.

ENxrmaFJyBUCVk_CKG5v-K2xNTiu3MgIWsTdW1WsG1sWgZLKMWEKmzKfAFXftLPfcdxWfS4qHAsQW4s60CKy25KltEKjlWaFbYmpSCMSw86DZy3k1yI8_-1PWYjBKcH0fIAbGhJIvBAGahseiv-o6fIg3ka3YxTdzkX_8V1YtfZt6dnAmE6se13AjriZdToNEUV2cDDjGkGcCsMvUJDtgOH0PdMAa0f7-eaXkPuUhodbggLqfxbiOCSDbhfEpH2il_wV9IdevNksjc-Q1kZ_aHXiD9GihlXPcFjnKJA3MOkIZuxcwvl--Mzlna2aB7dJ03fcYuJD3WuPHkQCL1t71QjahWe0ywUlerdM3SKHps8-qfIpFYG897uOoCqr2PPlp7U-yS-5axjr_aYDpYVrvQ5CDQrKllaXQ-SAaUtsaDsYS0IRThiRuXfE0qSr83wyL_MIjKU8vYGEQgUwbT4kC2g7Yy2wqXLlqy4svZrDBDaYCdA7did-MGS9LpmFci_IX15q3t5IYzBi1wtNkXZPDXn08c_Vvx0pk8UXe-UVzOv1z_ak3wKQefZFW_Gk7KivRbHjVqbmUWHkqupo33KFOEO3XQISJi5ASo66OVlwsV7RrqjWhllD=w635-h574-no
 












Interesting. I've never heard of this type of a device/tool. It sounds like it might work in your situation, but even if it does work as advertised you'll still end up with a certain percentage of missing threads at the top. I'd be very careful installing the plug in that hole and I'd be very nervous torquing it down. Personally I'd rather go the Helicoil route. The last time I looked the Helicoil kit (in stores) it was around the same price as that tool.

Here's an example of what the kit looks like and it's under $20:
http://www.ebay.com/itm/Metric-Thre...hash=item35ffecd9b0:m:mUh9_E5obhp_AGG_PylLJBw

I know a Helicoil repair will work and the resulting repair will be stronger than the original threads. You may need to take the P/S pump and maybe the A/C compressor loose either way to access the #4 spark plug hole. I know it's a really tight area to work in.
 






More bad news.

I purchased the back tap and used it on #4; spent close to 2 hours, running it through again and again. It's a pretty neat tool (wish I'd started with that in the beginning) and I eventually was able to thread a new plug in by hand, then tighten it down. So far so good, until this: Since I had all plugs in again, I decided to start the motor up; I could instantly hear a new, very noticeable valve "tick" noise, coming from 4 or 5, and things just feel rougher.

Not sure what happened but might have some valve damage now. Also, it's clear to me now that #5 plug is angled very differently than others, not threaded correctly at all.

Sucks. What a mess.
 






Update: Somehow... Good News

I mentioned earlier that #5 plug was in at a wonky angle, so I pulled it this evening and got my new "back tap" in there for several (like 10 or more) slow passes. You have to go nice and slow and clean it thoroughly between each pass, but that tool can pull off some amazing repairs. When finished, I was able to thread the plug back in at the correct angle and torque it down.

I started the engine and... no tapping, nothing strange, just idled like it always has. Took it out on a 20 mile drive on local roads and highway, and it felt good—for a 20 year-old Ford w/225,000 miles. :)

So, I guess that, initially, the #5 plug was angled enough to make slight contact with one of the valves, creating the tapping sound (no trace of that now). Anyway, I feel like maybe I dodged a bullet this time, but I'll keep you guys posted.

Hallelujahs are happening over here tonight.
 






WHAT ??
I thought you were... :dead:

Awesomeness !

:chug:
 



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WHAT ??
I thought you were... :dead:

Awesomeness !

:chug:

I thought I was too! I've been driving around town now for a couple days now, with zero issues. The "back tap" seemed to do a great job of cleaning/straightening threads on this old truck. I probably spent a good hour+ on each hole with it—so, if you've got the time and some finesse, I highly recommend it!

This all started, of course, with me thinking I would do a quick plugs/wires job. I have to admit that I'm not real confident about continuing to replace the other plugs at this point... might just put that off, for now.
 






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