Correctly torquing down spark plugs...
Discussion
Just how important is it to use a torque wrench when fitting spark plugs?
I'm about to service my GF's car and the plugs haven been out for about 3 years so im concerned that 1) - their gonna snap, if that goes OK im a little apprehensive about putting the new ones in.
I have a torque wrench but it starts at 28 nm and the KA's spark setting is 15 NM.. Will just an normal socket set do the trick? Just put them in snug and it'll be OK yeah?
I'm about to service my GF's car and the plugs haven been out for about 3 years so im concerned that 1) - their gonna snap, if that goes OK im a little apprehensive about putting the new ones in.
I have a torque wrench but it starts at 28 nm and the KA's spark setting is 15 NM.. Will just an normal socket set do the trick? Just put them in snug and it'll be OK yeah?
Silent1 said:
sidgolf said:
some copperslip on the threads would be a good idea aswell
You're taking the piss right?My Fiesta has a cast iron head, hence it's rust-tastic. If I don't put copaslip on the threads and sealing face of the plugs, then they rust in there solid and shear when I try to undo them.
So not a silly idea, no. It will however require less torque to do them up, so that should be taken into account.
I don't know anyone who uses a torque wrench to insert plugs, and I know a lot of mechanics.
So not a silly idea, no. It will however require less torque to do them up, so that should be taken into account.
I don't know anyone who uses a torque wrench to insert plugs, and I know a lot of mechanics.
qooqiiu said:
Just how important is it to use a torque wrench when fitting spark plugs?
I'm about to service my GF's car and the plugs haven been out for about 3 years so im concerned that 1) - their gonna snap, if that goes OK im a little apprehensive about putting the new ones in.
I have a torque wrench but it starts at 28 nm and the KA's spark setting is 15 NM.. Will just an normal socket set do the trick? Just put them in snug and it'll be OK yeah?
No need to use a torque wrench, the danger though is, as others have said, overtightening.I'm about to service my GF's car and the plugs haven been out for about 3 years so im concerned that 1) - their gonna snap, if that goes OK im a little apprehensive about putting the new ones in.
I have a torque wrench but it starts at 28 nm and the KA's spark setting is 15 NM.. Will just an normal socket set do the trick? Just put them in snug and it'll be OK yeah?
Somewhere on the NGK website are instructions for tightening plugs, old being slightly different to new.
No need to lubricate new plugs, they usually have a light lubricant on them, so don't wipe the threads.
Start by hand and they should screw in nearly all the way before you need any extra leverage. An old trick for deep plugs is to slid a piece of hose over the plug and use that to insert the plugs so that if you get the threads crossed the hose will slip, hopefully stopping any damage.
You'll get a feel for it, it's probably something like 1/8th of a turn after the washer touches the head but here's a couple of suggestions:
Use a spanner with a short bar, definitely not a torque wrench. I use a 15mm long bar, then hold it in the centre - not at the outer end. It's unlikely you could apply enough torque to damage the threads this way.
When you reach the right torque, the spark plug will stop turning. That's all you need to do, turn it until the washer touches (easy), turn a little to compress the washer (moves a little but stronger resistance), then stop.
If anything, it's better to have them a bit loose, rather than overtightened. You can always check them after a week or two, to see if they will 'nip up' a bit tighter. Whereas you can't undo thread damage so easily.
Oh, lastly, I've never snapped a spark plug, but when taking them out make sure the plug spanner is completely on the spark plug, and it should have a rubber insert to keep it centred. Use a long bar (eg torque wrench) and be prepared to use some force. The only way to screw it up, IMO, is if you let the plug socket slip off while you're doing this, so try to keep everything lined up at right angles, don't twist the socket relative to the plug.
Use a spanner with a short bar, definitely not a torque wrench. I use a 15mm long bar, then hold it in the centre - not at the outer end. It's unlikely you could apply enough torque to damage the threads this way.
When you reach the right torque, the spark plug will stop turning. That's all you need to do, turn it until the washer touches (easy), turn a little to compress the washer (moves a little but stronger resistance), then stop.
If anything, it's better to have them a bit loose, rather than overtightened. You can always check them after a week or two, to see if they will 'nip up' a bit tighter. Whereas you can't undo thread damage so easily.
Oh, lastly, I've never snapped a spark plug, but when taking them out make sure the plug spanner is completely on the spark plug, and it should have a rubber insert to keep it centred. Use a long bar (eg torque wrench) and be prepared to use some force. The only way to screw it up, IMO, is if you let the plug socket slip off while you're doing this, so try to keep everything lined up at right angles, don't twist the socket relative to the plug.
Edited by -Pete- on Tuesday 10th August 17:06
It's actually pretty important according to one of NGKs resident engineers here in the UK.
Most of the heat transfer from the plug is transmitted through the thread and sealing cone/washer. They should be torqued to 25Nm. Also, a 'small' dab of copper slip will prevent the threads sticking and has no detrimental effect. However, it's recommend to drop the tightening torque to 22Nm if copper slip is applied.
Most of the heat transfer from the plug is transmitted through the thread and sealing cone/washer. They should be torqued to 25Nm. Also, a 'small' dab of copper slip will prevent the threads sticking and has no detrimental effect. However, it's recommend to drop the tightening torque to 22Nm if copper slip is applied.
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