Spark plugs and anti-seize

My 2001 Classic has been running the same spark plugs for 212000 kms; according to the previous owner's service records, they were apparently inspected at one point and re-installed, but they haven't been touched otherwise.. A couple of weeks ago, the Canadian Tire had the NGK Iridium IX on sale, so I figure that it would be a good opportunity to replace the plugs, as the engine has been stumbling and hunting a bit in the first few minutes of starting in the morning since the cooler weather has arrived..

I quickly look through the section in the repair manual to double-check the procedure and WTH?? It says to remove the air cleaner box to get at the plugs, but looking at the car, there's absolutely no need to remove the box; instead, what you do need to remove is the relay box mounted over the plugs, but the manual mentions nothing about that at all (and in fact, their line drawings all show the relay box still installed).. Anyways, left the air box on, took off the relay box instead.. Took off the bolts holding down the coils, no problem, pull the coils out: #1, 2, 3, no problem.. #4, the rightmost coil is under a cable and you have to fight this cable as well as the short length of wire from the harness in order to pull this one out, but it does eventually come out..

OK, now for the plugs.. #1, wrench in, plug doesn't budge.. Ok, save it for later, try #2, this one is tight, but it makes a "pop-pop-pop" sound like the socket is slipping (but it isn't, it's the sound of an almost-seized plug breaking free from the aluminum head- and I almost stop here and retighten the plug and give up, having visions of stripping the head and having to tow it to the dealership, a simple job going horribly wrong), but one more turn and the pops stop and I hear the plug threads squeaking as the plug unscrews; a couple more turns and the squeaks stop and the plug comes out reasonably easily.. I look at the threads, and there's minor corrosion and deposits and there is absolutely no signs that any kind of anti-seize was used at all- what the heck were you thinking Toyota?? Who puts a set of plugs designed to go hundreds of thousands of miles in an *aluminum* head without anti-seize??

Anyways, the plug is in not too bad a condition, electrodes and insulator are reasonably clean, but right around the top of the thread is a black/brown baked on deposit.. The iridium tip is still in good shape, but the ground electrode has minor pitting around the end.. The plug could probably still be cleaned off, and the ground electrode gently filed, regapped and placed back in service, but they've been in service for over 200,000 km and I've already bought new ones, so I might as well replace them..

New plug has gap checked, a good grade of anti-seize lubricant placed all over the threads and goes back in the engine.. With the lube on the threads, it goes back in butter smooth, no squeaks or anything.. OK, one plug done.. #3 is exactly the same as #2, a few pops as the plug breaks free, then squeaks and the plug is out.. Same thing, no antiseize on threads, some deposits near the top of the threads, iridium tip is in good condition, but ground electrode is a bit pitted.. Again, new plug with plenty of antiseize on the threads and it goes back in easily..

OK, plug #4, and like #1, it doesn't move either.. Go back to #1, and reef it a bit harder- "pop-pop-pop", then it stops dead.. Reef it again, more pops, and finally "squeak!" and the plug starts to come out- this one is quite rough like the thread is very dirty, and indeed, once out, the threads on this plug are worse than the centre 2 plugs.. Get the new one out, lube and re-install- 3 out of 4 done, so go back to #4 and try again.. This stupid plug won't budge and I'm afraid of using more force for fear of stripping the aluminum, so I try tapping the end of the wrench with a hammer in hopes that some impact might break it loose.. After 5 minutes of tapping, the plug has moved about 1/2 a turn, but it still doesn't move with any reasonable hand pressure, this one is really in there good.. I give the hammer a few more good whacks, in reverse hoping that maybe the back-and-forth might break the plug free and this seems to have done it- the plug is "popping" now, I go through 4 or 5 turns of popping sounds before I finally get the squeaky thread and then a few more turns later, the plug comes out.. I inspect the threads carefully for any signs of aluminum pieces that might indicate thread damage, but there are none, just lots of deposits and corrosion and again, no signs of any use of anti-seize compound...

So finally, replaced the last plug, go back through and retorque all the plugs, reinstall the coils, again fighting the #4, the rightmost coil that has a short wiring harness and has to go under a cable- going back on is actually more tricky than getting it off because the thing has to be aligned so that it goes on the contact at the top of the plug.. I use a bit of anti-seize on the coil bolts as well as I've got lots left in the little foil packet.. Bolt the relay box back on, and it's all done- start the car, and am rewarded with a nice smooth idle, everything is good, but taking those plugs out of the aluminum head and the odd noises had me on edge the whole time.. Anti-seize on the plug threads is not only a good thing, it's IMO a necessity.. If you're planning on changing your plugs soon, be sure to spend the extra $1.50 and buy the packet of anti-seize; it might even be a good idea on newer vehicles to take the plugs out now, before they've had a chance to seize, and put some lubricant on the threads and re-install them so that when you do eventually have to replace them, that you are able to easily remove them without risking damage to the aluminum head.. Why Toyota, who seem to think of everything else, would install plugs without anti-seize still amazes me..

 

<div class='quotetop'>QUOTE(tochatihu @ Sep 22 2006, 05:27 PM) [snapback]323594[/snapback]</div>

It wasn't in the vertical direction, if you read again carefully, I was tapping the handle end of the wrench, which basically mimics the impact action: instead of a constant torque, which will tend to shred the threads, you apply momentary impulses of fairly high torque which has the effect of breaking a seized surface free without stripping.

I suppose a mention of the proper anti-seize to use is in order- it must be conductive (for obvious reasons), capable of withstanding high temperatures andcompatible with aluminum. This generally means a copper based anti-seize, although nickel and silver-based materials are also OK (silver isn't quite as good for high temp; nickel is good for high temp but not rated quite as compatible with aluminum as copper).. There are also various proprietary grades from Loctite and other companies that contain various mixtures of metallic and non-metallic particles that may also work- but before you use it, do check to see that the stuff is suitable for the application (the stuff you use for wheel lug nuts for example does not need to be conductive nor high temperature)