Am I being a bit dim? (Socket/Spark Plug content)

Thought I’d nip out and change the spark plugs on the car. So I measured the new plugs: 14mm. Then look for my wrench: 21mm. D’oh!

Oh well, I have a spark-plug socket somewhere. Find it, and success! It says ’14mm’ on the side. ‘Halfords Advanced 14mm CR-V’ to be exact. Thing is; it might say 14mm, but it clearly isn’t. It’s 21mm! As in the actual hole in the socket that sits over the bolt/spark plug.

What’s going on here, am I missing something obvious?

They thoughtfully measure the thread size on spark plugs, not the bit you attach the socket to.

Que? I measured the plug myself. Not the thread, the bolt bit. It’s the socket I’m confused about. Why would it say 14mm when it’s clearly not?

Why would it say 14mm when it’s clearly not?

A 14mm spark plug socket is designed to fit a spark plug that’s designed to go in a 14mm hole.

Ohhhh….

😀

What bit did you measure on the plugs? As wwaswas says, the size written on spark plug tools refers to the diameter of the threaded section, not the size of the bit the spanner fits onto.

Ohhhh….

bonkers isn’t it 🙂

I measured the six-sided bit that the socket fits onto. Which is 14mm. So you’re telling me a 14mm spark-plug socket is not the correct socket to fit these plugs?

AAAARGH

🙂

You tend to find most threaded items (Bolts/Nuts/Screws) are described by their thread form (i.e. M6/M10/M14) I can’t see why a spark plug would be much different.

the AF dim might be provided in some supporting literature, it won’t typically be listed in a basic product description or PN but it’s not usually too hard to figure it out by just trying a couple of sockets on TBH.

Just did this myself too. I had two sparkplug sockets, both obviously not the size they said on the side.

The rubber bit that holds onto the plug end kept falling out and attaching to the plug. So I had to glue it in place.. then the pull required to remove the socket from the screwed in plug was more than the tug required to release the socket from the extension bar I had to use to access the plug down the deep hole in the head.. bah..

cookeaa – the only items in my socket sets that don’t have the size of the bolt head (not the threaded part) they’re intended to fit written on them are the spark plug sockets?

molgrips – a bit of rubber fuel pipe shoved on the end of the spark plug will often grip well enough to lift them out.

Just open your socket set drawer and use the one that fits.

I is still confused…

I is still confused…

Obviously; you’ve picked up your ruler instead of your calipers.

Just use the one that fits or I’ll start calling you poppet.

measure the threaded bit that currently has the plastic cover on it – it’ll probably be 10mm.

You then need to find a 10mm spark plug socket.

So what happens when you try the tool on the spark plug? Does it fit? Is the tool too big or too small?

wwaswas +1. That’s a 10mm spark plug. Time for another trip to Halfords

Just use the one that fits or I’ll start calling you poppet.

😀

So what happens when you try the tool on the spark plug? Does it fit? Is the tool too big or too small?

It’s much too big… fnarr

measure the threaded bit that currently has the plastic cover on it – it’ll probably be 10mm.

You then need to find a 10mm spark plug socket.

*penny drops*

Does one count from the ridge of the thread, or the ‘valley’? It’s either 12 or 13mm

take the spark plug to Halfords.

buy the socket that fits it.

🙂

[edit] there is a 12mm size too, btw.

Does one count from the ridge of the thread, or the ‘valley’? It’s either 12 or 13mm

It doesn’t matter.
Just go to *Halfords and buy the biggest set they sell, you obviously need to.
Then you’ll definitely have what you need.

*I have no affiliation to Halfords, if you happen upon a travelling Snap-on salesman you could always acquire said tools from him, in exchange for your first and second borne children, and probably a go on your wife though you get her back afterwards.

take the spark plug to Halfords.

buy the socket that fits it.

Will do.

Thanks all. Check back later for ‘Bolted my head to engine block; what to do?’

Just go to *Halfords and buy the biggest set they sell, you obviously need to.

Yeah, I’ve been tempted by those half-price offers. Could be the perfect excuse I’ve been looking for…

What’s that saying about a horse and water? 🙂

Just check if you need a thin walled socket if space is tight! 🙂

Could be the perfect excuse I’ve been looking for…

Could?

COULD?

It’s worth getting a socket set if you don’t have one – BUT what you really need is a spark plug socket. These are longer than ordinary sockets & often have some soft insert to hold the spark plug when you are putting it in or taking it out. There are a couple of different sizes – but if you ensure you get the right size spark plugs for your car (either use the Halfords look-up cards or ask a salesperson – then get one to fit. They may come in with a socket set or not depending on the set & the size of plug you need.

Also be careful not to over tighten spark plugs when you put them in. A bit of copper grease on the threads to prevent seizures & a torque wrench is useful and knowing the correct torque to be on the safe side.

For the life of me, I only remember spark plugs ever coming in “big ones” and “little ones.” What you’ve got there is a little one, which is why your socket doesn’t fit – it’s for big ones. You need one for little ones instead.

Sorry if I’ve got a bit too technical in my explanation there.

Careful not to go full retard and over tighten em like a complete fud.

Torque wrench on a spark plug….really ? Next youll br telling em you torque on your exhaust heat sheild.

I’m sure any experinced home mechanic / tinker could torque spark plugs by feel.

But for someone who’s obviously not so experinced a torque wrench might not be a bad idea, especially in an ally head.

Or use angle as a guide….

http://www.ngk-sparkplugs.jp/english/techinfo/qa/q18/index.html

Although again experince helps gauge how snug to be before the final tightening angle.

Or use angle as a guide….

That’s what I always did, as dictated by Haynes.

Well, job jobbed. Car feels a lot sprightlier. At least I’ve got both sizes now. Thanks for the technical explanation Cougar 🙂

I did them up by hand first with just the socket and extension bar (without the wrench) then snugged them up with the wrench on. Only annoying thing was one of the bolts that holds the air box down sheared on re-fitting. It’s still pretty secure so not the end of the world.

Believe it or not, I’ve changed the plugs on loads of my cars, I just didn’t drive for a long time and gave away most of my tools. I guess I just used to ‘see which one fits’ 🙂

Don’t go to Halfords. find your local motor factors, build a relationship with them. They will be cheaper and have infinitely more experience that anyone working for Halfords.

I have a really handy tool for replacing spark plugs. Made by Facom, though I cant find an image. Its like a flexi shafted screwdriver with a piece of rubber tube at the drive end. You inset the insulated end of the plug into the tube and then you can screw the plug in place. Its especially handy where the plugs are deeply recessed into a twin cam head. The grip the rubber has on the plug is less than the plug’s capacity to cross thread. Once its in place just use a plug spcket and torque wrench. Be especially careful with the torque setting on an alloy head.

Facom make a torque limiting ratchet for spark plugs, I shudder to think what they cost.