Torque wrench for spark plugs


#1

Hi, I am a new DIYer and went to change my plugs in a 2005 Accord V6. Most people I asked for a torque wrench told me not necessary and so I went to do it by hand lightly. The car idled roughly and when I went to check on the plugs they were pretty loose, a HAIR past hand tightened. Definitely looser than my hand tighten and then 1/8 to 1/4 turn.

So I tightened them, all but the back right one. Now, afraid that I’ve over tightened them, I would like to ask what is a good torque wrench for spark plugs? I can’t find one good for 13 lbs, also, now that I’ve definitely crushed the steel washer on the NGK iridium plugs OEM to my car, how much torque do you think that might be? 16/17 lbs now needed?

Thanks and I’m sorry if this is repetitive. It’s surprising how hard it is to find a decent torque wrench for this.


#2

I’ve NEVER used a torque wrench for spark plugs. And I don’t understand why you can’t find a torque wrench for 13lbs.


#3

I can, but don’t want to spend $100+ for an accurate one… I would really just like a suggestion on this one.

The thing is, I went too loose, now I’m worried too tight and in awhile they’ll be impossible to move.

darn crush washers…


#4

You can get a beam-type torque wrench at Sears for abou $25. I like them for occasional use because they remain accurate and are extremely durable. Remember in selecting one that to get accuracy at 13 ft lbs a wrench that goes to 150 lbs is fine. The rule of thumb is that the desired reading range should be away from the scale’s ends’ with sufficient divisions to inrterpolate the reading. Remember too that the torque does not have to be exact and that the plugs’ specs will have a range.

http://www.bing.com/images/search?q=beam+type+torque+wrench&qpvt=beam+type+torque+wrench&FORM=IGRE


#5

If you want a halfway accurate torque wrench for low specs then you need a 3/8 or 1/4 drive. My opinion is that 1/2 drive torque wrenches are a bit iffy at specs that low.

Personally, I do not use a torque wrench on plugs and trust feel more than a spec that may cause more trouble than any help it offers.
I would never run a plug down to 16 Ft. Lbs in an aluminum head. While it may not strip the threads it could certainly pull them a bit and eventually lead to stripped threads. There’s also the issue of not really knowing if those threads that you’re applying that kind of torque to are in good shape or not.

If you ran them down to snug, added a quarter turn, and they came loose quickly then there may be a thread issue already.

(Regarding torque specs, I’ve seen some specs given as 7 to 15 Ft. Lbs. That’s a pretty broad range to throw at something and is near meaningless because of that.)


#6

This one looks good. The last question I have is, with a spark plug extension, wouldn’t the torque settings be off? I’m obviously new to cars, but the physics here is pretty simple and seems like an extension would change the torque.


#7

Why would an extension change the torque unless there was torsional flex in the extension?

To be honest, you’re going for high-accuracy in a situation that doesn’t call for it. If you want to do it just to do it, that’s fine, but just hand tightening the spark plugs works just fine. Since you didn’t tighten them down enough last time, tighten them a little more this time. Putting a torque wrench to it isn’t going to do anything but make you spend money on a torque wrench that, unless you do things like change your own clutches, isn’t very useful for anything but spark plugs (which will irritate you when you have to torque down an axle nut and have to buy a higher-torque one).


#8

Not significantly. You’re talking small torque amounts with wide ranges. The only affect an extension would have is the energy lost in the twisting of the extension shaft. If you were talking huge numbers and/or an extrememly long shaft, some of the torque would be absorbed by twisting of the extension shaft and converted to heat energy, but that ain’t the case with numbers in the 20’s and a 9" extension. At least not to where it would affect the numbers to the accuracy that you’re looking for.


#9

An extension that attaches to the square drive part of the ratchet and runs perpendicular to the ratchet handle will not change the torque.

Only an attachement like a crow’s foot will change the torque. And yiu won’t be using a crow’s foot to change a spark plug.

So, the short answer is that any extension you would use on a spark plug will change the torque.


#10

Oops, bad typo above: “any extension you would use to change a spark plug will NOT change the torque…”

( iPads bad for typing on…)


#11

Gotcha. Thanks for the explanation.

Shadow - I tried to hand tighten and then turn them until still, little less than a 1/4 turn… and they got loose and my car was idleing roughly. I don’t want to spend money trust me. My other cars were no problem, but then again I wasn’t buying expensive plugs designed to stay in for so long.

I guess technically I could just leave em tight and sell it off to the next person to deal with, but bad karma and all.


#12

There shouldn’t be any issues with removing the plugs after being in the engine long term if you used anti seize on the threads. Maybe I’m different to everyone else, but I’ve never used a torque wrench on spark plugs. I just snug the down good without being excessive.


#13

NGK iridiums have a TSB not to use anti seize.


#14

If it were mine I’d remove them and replace them using a torque wrench. OK4450 has installed hundreds, perhaps thousands, of plugs, and torqued thousands of other bolts, and I’d be perfectly comfortable with the accuracy of his feel, In your case a torque wrench is a good idea. The cost of a problem shoudl the plugs work loose and strip part of the threads out could escalate.


#15

See if you can find an inch-pounds torque wrench. You just multiply the foot-pounds by 12 to come up with the equivalent foot-pounds value. Fair advice for plugs: Don’t keep retightening them, it’s inviting trouble. If you think it’s a little tight, leave it alone.


#16

You sound like a cautious person, since the first time around you barely tightened the plugs at all.

Now, the second time around, you’re worried that you overtightened them. But I doubt you tightened them enough to damage threads, given the above.

If you did damage the threads in the head, removing the plugs and retorquing them isn’t going to fix the threads. But again, I doubt you did any damage.

I’d advise you to just leave them alone. Check them again in a few weeks. If they’re still tight, you’re fine.

In 40k miles or so, when you want to install new plugs, take the car to an experienced friend or a local shop and have the friend/mechanic give you a short lesson in torquing the plugs by “feel.” Don’t waste your $$ on a torque wrench you might use once every couple of years. Buy yourself some car parts instead…like oil, filters, and spark plugs…


#17

Can you get at the rear plugs with a torque wrench and a straight adapter? If not, just tighten them as best you an with a ratchet, extension, and universal adapter. And why isn’t antiseize compound recommended?


#18

I’ve never used a torque wrench but have been putting plugs in go carts, mowers, bikes, etc. since I was 12. I just snug them with the ratchet and then another snug. I don’t know how you would get a torque wrench into some of the tight spaces now. I can barely get my hand back there.


#19

All good info here. Want to add that I bought a cheapo 3/4 torque wrench from harbor freight and it has lifetime warranty.

Word of caution, 1st time using the T wrench, increase the torque settings gradually from lets say 8 to 13 to make sure you won’t over-tighten them. The wrench itself is large and you can make things tighter than they should be.

Also, even though I don’t have much experience, I use the T wrench for transmission pan installations, but have noticed that even if I go by feel, I just do fine. So just tightening them by feel should work fine.


#20

I assume you mean 13 foot pounds. That’s the rotational force exerted if you pushed with a force of 13 pounds at the end of a 1 foot long wrench.

Inexpensive torque wrenches that I think would work for you are available at Harbor Depot. But if you don’t have a torque wrench, you can make a pretty good estimate using a plain combo-wrench or ratchet handle. If the handle is one foot long, push on the end of it with a force of 13 pounds Don’t know how much 13 pounds is? Take your bathroom scale out there and push on it. Then use that same amount of force pushing on the end of the handle.

I always spread a thin layer, just a tiny amount, of moly-lube on the spark plug threads btw, it makes it easier to set the torque, and it makes it easier to remove the plugs later.