2000 4R Spark plug came out while driving
 

2000 4R 204k miles. I pulled away from a stop light and got a loud rattle when accelerating. My first thought was a u joint so I limped home. In the drive way I got the same noise while not in gear so not a u joint. A buddy was looking under the hood when I gave it gas and it back fired from the top of the engine. Started pulling plugs and the #3 plug had come out of the head and was rattling around in the tube that goes through the cylinder head cover.
The problem is that in the short time it was driven and run the plug damaged the threads in the head so I can't get a new plug to start.

Is there a way to re-tap the thread (then blow and vacuum the shavings out of the cylinder) without taking the passenger side cover and head off or will I have to replace the head?
Ideas??

Blew a spark plug out of the block! - Toyota 4Runner Forum - Largest 4Runner Forum

Spark plug blew out - helicoil? - Toyota 4Runner Forum - Largest 4Runner Forum

TIME SERT KIT for Spark Plug Re-threading - Toyota 4Runner Forum - Largest 4Runner Forum


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Looks like a common problem. Thank you for the links.

Man, who would have thought this was a common issue! I would have assumed it to be such a unique thing I’m not sure I would have even tried to search if it had happened to me.

This one of the few, few bad design things on these trucks. I always say, never send aluminum to do iron/steels job. Lol

Good luck buddy!

Just to cheer you up, at 273K my 99 blew the spark plug out of #1 Cylinder, broke the coil too. I put a Time-Sert kit in it, and a new coil. I now have 336K and no further problems. Always use anti-seize on spark plug threads!

:couch2:

I use anti-sieze , does it help prevent a blowout or were you just saying it's good practice?

Anti-Sieze helps to prevent Galvanic Corrosion from the dissimilar metals. The Spark Plug is Steel Threads, and the block is Aluminum. Torque specs is 13 ft-lbs from what I can find.

I had this problem on my Land Cruiser, same basic head design with the long tube design. I ended up with a Heli-Coil brand kit and used Red Loctite to secure the Heli-Coil to the head per a few of the videos I watched on the subject. I sold it not too long after, and so far it's given the new owner no issues.

Use a lot of GREASE and only cut 1 or 2 threads at a time. Back out, clean the grease/chips, and slap more grease on. It took me about 30 minutes of back and forth to cut the threads all the way through. Take your time and you won't drop any chips. You can use a shop vac on reverse hooked up to the Tailpipe to pressurize the cylinder and blow any chips out. I used a scope to confirm no chips.

Funny you mention to always use anti-seize.
Picked up a set of NGK plugs today to throw in when I do valve cover gaskets later this week and their website says no to anti-seize as their plugs have a coating applied at the factory to eliminate need.
Now i’m rethinking which way to go.

I just put the tiniest dab on the 2nd thread and use a pick to smear it into the thread. Never had a problem doing it that way on any of the vehicles I've changed plugs in, including friends vehicles.

Torque the plugs to 13 ft lbs per the service manual, and keep on 4Runnin.

On this forum and in other places I have quoted NGK's position WRT anti seize.

A recent experience has changed my mind. First, it's not clear when NGK began the claimed plating of their plugs. Second, it's not clear how long that protection-by-plating is supposed to last.

It's like when a maker of roofing materials promises its new shingle will last 30 years. A British admiral once said - I've never been able to track this down - that the best scale for simulation (ie, war games) is 12 inches to the foot.

Meaning, the truest test of weapons and strategy is combat.

Now, back to NGK plugs. In 1991 I inherited my uncle's Honda CB400F. That summer I rode it from CO to WA. I (probably) installed new NGK plugs that fall. I don't recall if I used anti-seize.

The bike was ridden just a few times, less than 100 miles, in the intervening 29 years. The last time was maybe 10 years ago. The plugs were never removed.

Due to the quarantine, and inspired by the splendid YouTube videos of Allen Millyard, I decided to get that old Honda out and change its oil and do whatever else was needed.

3 of the 4 NGK plugs were seized and broke off, though I'd tried all the tricks to free them up. I removed the head and dug out the remains - effectively a small threaded tube 12mm in diameter by 17mm long. The 3 holes might be usable, but I'm going to install Time Serts.

Now, I don't know if those 1991 plugs had NGK's special plating; I suspect not. I do know that 29 years of steel and aluminum in close proximity might negate plating and even anti seize.

One complaint about using anti seize or even oil on spark plug threads is that it interferes with heat transfer away from the plug. I think that might be a valid issue on racing engines, particularly air cooled racing engines, such as 2-stroke motorcycles.

I think the claims of NGK's engineers about the effectiveness of their plating are correct, but maybe only for a few years.

When I put plugs back into that Honda, they'll have anti seize on them, and I'll make a note of the date they were installed, and revisit them every few years.

To my understanding, bicyclists have some extensive experience with aluminum seat posts sticking inside the steel frame tube. Lots of links and videos out there on this subject.

PS I hope all the shade tree mechanics and machinists will check out some of Millyard's videos. Prepare to be badly humbled.

One important thing to remember is that anti-seize reduces friction in the threads, and therefore torque required to achieve your target fastener load is reduced. Because of this, if you use anti-seize and torque to spec you do risk stripping things out, especially if you are dealing with a weak/ thin piece you are tightening in to.

Yes, I’m pretty sure this was the reason for the NGK announcement.

Installing plugs in a hot engine may also promote pulling the threads.


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13ft lbs. If using torque wrench make sure the wrench is calibrated. cheap torque wrenches aré notoriously off. I don't use a torque wrench for spark plugs. just goodentight.