DIY spark plug change
Discussion
Planning to change my spark plugs first time DIY this weekend.
When reading guides online I see mentioned clearing the cylinder head etc. with compressed air. Any tips on how you would do this without a specialist tool? I'm sure I could pop out and get something if necessary.
Also, are there any common mistakes to watch out for when changing sparks?
I've got the spark plugs, a gap feeler gauge and a torque wrench. I've also contacted the manufacturer and have the correct gap and torque settings for the plugs.
When reading guides online I see mentioned clearing the cylinder head etc. with compressed air. Any tips on how you would do this without a specialist tool? I'm sure I could pop out and get something if necessary.
Also, are there any common mistakes to watch out for when changing sparks?
I've got the spark plugs, a gap feeler gauge and a torque wrench. I've also contacted the manufacturer and have the correct gap and torque settings for the plugs.
Plugs should screw in and out finger tight apart from the final turn when they bottom out against the head. You might find it helps to use the plug socket (without anything connected to it) to make it easier to grip the plug. Be very wary of cross-threading and be patient if you can't get the thread to engage - always do this by hand and make sure the plug spins down with finger pressure, don't force it under any circumstances.
If your plugs use the common crush washer for sealing, they will have a specific tightening angle for a new plug and a reduced angle for refitting a used plug.
Also, make sure your plug leads are labelled to show which plug they fit before you disconnect them - last thing you want is to be in any doubt which lead connects to which plug when it comes to to reconnect them. If you are not familiar with this engine, you might want to reattach the lead for each plug as you replace it before moving on to the next plug, so there is no doubt which lead goes to which plug. (Experienced mechanics will get all the plug leads out of the way for speed/convenience.)
If your plug leads have boots which seal to the plugs (many good quality leads have this) make sure the boots are fully home and don't have air trapped under them - it's common for these to pop off when they heat up if they have air trapped underneath.
If your plugs use the common crush washer for sealing, they will have a specific tightening angle for a new plug and a reduced angle for refitting a used plug.
Also, make sure your plug leads are labelled to show which plug they fit before you disconnect them - last thing you want is to be in any doubt which lead connects to which plug when it comes to to reconnect them. If you are not familiar with this engine, you might want to reattach the lead for each plug as you replace it before moving on to the next plug, so there is no doubt which lead goes to which plug. (Experienced mechanics will get all the plug leads out of the way for speed/convenience.)
If your plug leads have boots which seal to the plugs (many good quality leads have this) make sure the boots are fully home and don't have air trapped under them - it's common for these to pop off when they heat up if they have air trapped underneath.
Edited by GreenV8S on Friday 25th August 15:11
It is best to have the correct plug socket with the rubber insert
Where it is sometimes difficult to access I often use the plug socket on its own with out the wrench or extension bar to guide it and finger tight the plug as described above
The compressed air exercise is just to blow the dust and swarf away but a hoover could do that job but I only ever go over with a rag
Take your time
Where it is sometimes difficult to access I often use the plug socket on its own with out the wrench or extension bar to guide it and finger tight the plug as described above
The compressed air exercise is just to blow the dust and swarf away but a hoover could do that job but I only ever go over with a rag
Take your time
Thanks for the replies.
I plan to take a picture of the engine prior to the job to ensure I get the plug leads correct. If it's not so clear I'll get some labels or something sorted.
I've found jobs always take longer than expected, very rarely does it all go to plan!
It looks to me like the plugs will be easily accessible. It's my girlfriends Hyundai i20. The engine is very small and not too much unnecessary crap in the engine bay.
GreenV8S said:
Plugs should screw in and out finger tight apart from the final turn when they bottom out against the head. You might find it helps to use the plug socket (without anything connected to it) to make it easier to grip the plug. Be very wary of cross-threading and be patient if you can't get the thread to engage - always do this by hand and make sure the plug spins down with finger pressure, don't force it under any circumstances.
If your plugs use the common crush washer for sealing, they will have a specific tightening angle for a new plug and a reduced angle for refitting a used plug.
Also, make sure your plug leads are labelled to show which plug they fit before you disconnect them - last thing you want is to be in any doubt which lead connects to which plug when it comes to to reconnect them. If you are not familiar with this engine, you might want to reattach the lead for each plug as you replace it before moving on to the next plug, so there is no doubt which lead goes to which plug. (Experienced mechanics will get all the plug leads out of the way for speed/convenience.)
If your plug leads have boots which seal to the plugs (many good quality leads have this) make sure the boots are fully home and don't have air trapped under them - it's common for these to pop off when they heat up if they have air trapped underneath.
Not so sure about the crush washer to be honest. These are the plugs if that helps: https://www.ngk.com/product.aspx?zpid=9953If your plugs use the common crush washer for sealing, they will have a specific tightening angle for a new plug and a reduced angle for refitting a used plug.
Also, make sure your plug leads are labelled to show which plug they fit before you disconnect them - last thing you want is to be in any doubt which lead connects to which plug when it comes to to reconnect them. If you are not familiar with this engine, you might want to reattach the lead for each plug as you replace it before moving on to the next plug, so there is no doubt which lead goes to which plug. (Experienced mechanics will get all the plug leads out of the way for speed/convenience.)
If your plug leads have boots which seal to the plugs (many good quality leads have this) make sure the boots are fully home and don't have air trapped under them - it's common for these to pop off when they heat up if they have air trapped underneath.
Edited by GreenV8S on Friday 25th August 15:11
I plan to take a picture of the engine prior to the job to ensure I get the plug leads correct. If it's not so clear I'll get some labels or something sorted.
jeremyh1 said:
It is best to have the correct plug socket with the rubber insert
Where it is sometimes difficult to access I often use the plug socket on its own with out the wrench or extension bar to guide it and finger tight the plug as described above
The compressed air exercise is just to blow the dust and swarf away but a hoover could do that job but I only ever go over with a rag
Take your time
Thanks. Definitely will take my time. Where it is sometimes difficult to access I often use the plug socket on its own with out the wrench or extension bar to guide it and finger tight the plug as described above
The compressed air exercise is just to blow the dust and swarf away but a hoover could do that job but I only ever go over with a rag
Take your time
I've found jobs always take longer than expected, very rarely does it all go to plan!
It looks to me like the plugs will be easily accessible. It's my girlfriends Hyundai i20. The engine is very small and not too much unnecessary crap in the engine bay.
Drew106 said:
Not so sure about the crush washer to be honest. These are the plugs if that helps: https://www.ngk.com/product.aspx?zpid=9953
Those appear to use crush washers.First time you're doing spark plugs and you're doing it on somebody else's car? I wouldn't fancy that. It's an easy job which people easily become blasé about but it can go wrong and if it does the results can be majorly expensive.
When refitting the plugs, dangle them into position using your spark plug socket and extension. Under the weight of the spark plug and the tool alone, slowly rotate the socket counter clockwise and you'll distinctly feel the plug drop into thread engagement. Then you know that when you go clockwise you are threading the plug in and not grinding the plug cack-handedly against the thread, probably with excessive force and at the wrong angle.
When refitting the plugs, dangle them into position using your spark plug socket and extension. Under the weight of the spark plug and the tool alone, slowly rotate the socket counter clockwise and you'll distinctly feel the plug drop into thread engagement. Then you know that when you go clockwise you are threading the plug in and not grinding the plug cack-handedly against the thread, probably with excessive force and at the wrong angle.
HustleRussell said:
First time you're doing spark plugs and you're doing it on somebody else's car? I wouldn't fancy that. It's an easy job which people easily become blasé about but it can go wrong and if it does the results can be majorly expensive.
When refitting the plugs, dangle them into position using your spark plug socket and extension. Under the weight of the spark plug and the tool alone, slowly rotate the socket counter clockwise and you'll distinctly feel the plug drop into thread engagement. Then you know that when you go clockwise you are threading the plug in and not grinding the plug cack-handedly against the thread, probably with excessive force and at the wrong angle.
No Russell its his girlfriend Dont you ever do things that p**s your partner off ! ?When refitting the plugs, dangle them into position using your spark plug socket and extension. Under the weight of the spark plug and the tool alone, slowly rotate the socket counter clockwise and you'll distinctly feel the plug drop into thread engagement. Then you know that when you go clockwise you are threading the plug in and not grinding the plug cack-handedly against the thread, probably with excessive force and at the wrong angle.
HustleRussell said:
First time you're doing spark plugs and you're doing it on somebody else's car? I wouldn't fancy that. It's an easy job which people easily become blasé about but it can go wrong and if it does the results can be majorly expensive.
Haha. Well it's kind of our car - I do the easy stuff like sorting the tax, insurance, MOT, servicing... she occasionally drives it lol. I'm pretty new to maintaining my own cars, but building up the spannering experience bit by bit. Always worried about f
king things up mind, but that's the idea behind asking advice on here. 
So really would you say the biggest potential f
k up would be cross threading the plug? Or over/under torqueing maybe? Got a shinny new torque wrench for just this task. Drew106 said:
Haha. Well it's kind of our car - I do the easy stuff like sorting the tax, insurance, MOT, servicing... she occasionally drives it lol.
I'm pretty new to maintaining my own cars, but building up the spannering experience bit by bit. Always worried about fking things up mind, but that's the idea behind asking advice on here.
So really would you say the biggest potential fk up would be cross threading the plug? Or over/under torqueing maybe? Got a shinny new torque wrench for just this task.
Sort of. Always give a thought to the materials and construction. The cylinder head is not easy to repair or replace without major work. It also happens to be made of comparatively soft cast aluminium while the spark plug is steel bar stock. If you do get it a bit wrong it ain't going to be the cheap and easily replaced spark plug which comes off worst. What happens sometimes is you go to replace the spark plugs and they're seized in or they've been overtightened or cross threaded by the previous mechanic. Then when you, with the best intentions, go to remove them the spark plug finally comes out and pulls all the threads out of the cylinder head with it. This kind of thing keeps me from working on other people's cars even though I'm reasonably competent.I'm pretty new to maintaining my own cars, but building up the spannering experience bit by bit. Always worried about f
king things up mind, but that's the idea behind asking advice on here. So really would you say the biggest potential f
k up would be cross threading the plug? Or over/under torqueing maybe? Got a shinny new torque wrench for just this task. Yes because it is never straight faward Haynes always tell you how to repair things but never tell you what may go wrong !
Last week I did a cam belt on a berlingo while undoing the crank sprocket a bolt snapped so on putting it back together I had to drill it and extract it
Yesterday on my Saab the distributor rotor arm would not come off at all . So I just broke it up with mole grips
There always appears to be an unexpected challenge but as for plugs in 30 years of doing it I have never had a problem I am very careful though and with the knowlege that if I f??k up I may have to remove the head and take it to an engineers shop . I am normally very careful with this in mind
Last week I did a cam belt on a berlingo while undoing the crank sprocket a bolt snapped so on putting it back together I had to drill it and extract it
Yesterday on my Saab the distributor rotor arm would not come off at all . So I just broke it up with mole grips
There always appears to be an unexpected challenge but as for plugs in 30 years of doing it I have never had a problem I am very careful though and with the knowlege that if I f??k up I may have to remove the head and take it to an engineers shop . I am normally very careful with this in mind
HustleRussell said:
When refitting the plugs, dangle them into position using your spark plug socket and extension. Under the weight of the spark plug and the tool alone, slowly rotate the socket counter clockwise and you'll distinctly feel the plug drop into thread engagement. Then you know that when you go clockwise you are threading the plug in and not grinding the plug cack-handedly against the thread, probably with excessive force and at the wrong angle.
This is excellent advice. In the absence of any other specific issues, it's the principal bit of good practice, the plug will almost click as it passes the start of the thread, at which point, you'll know you can screw it in safely. And do them one at a time, that way you can't reconnect the leads in the wrong firing order.Some excellent advice here guys, thanks. The bit about rotating counter-clockwise to find the thread is great. Very simple and I'm sure I've used this method before, but it is good to have these thing reminded to you.
In the end I didn't change the plugs at the weekend. OH needed the car for something and was told I couldn't break it lol. Like I would...
In the end I didn't change the plugs at the weekend. OH needed the car for something and was told I couldn't break it lol. Like I would...
Just resurrecting my thread for another bit of advice.
Planning to change the plugs this weekend. Didn't get round to it before, but it is not an urgent job anyway.
My question is just regarding when to do the change. I understand a cold engine is better, but does that mean completely cold, like first thing in the morning, or just cool? Or does it not matter so much?
Going to be doing and oil and filter change as well, so my plan is:
Saturday morning,
1) Change plugs on the cold engine.
2) Start it up to check everything is working OK and let the oil heat a bit before draining it.
Or I could do the other way round, i.e. after changing the oil.
Planning to change the plugs this weekend. Didn't get round to it before, but it is not an urgent job anyway.
My question is just regarding when to do the change. I understand a cold engine is better, but does that mean completely cold, like first thing in the morning, or just cool? Or does it not matter so much?
Going to be doing and oil and filter change as well, so my plan is:
Saturday morning,
1) Change plugs on the cold engine.
2) Start it up to check everything is working OK and let the oil heat a bit before draining it.
Or I could do the other way round, i.e. after changing the oil.
Do plugs cold. You will burn yourself on some part of the engine. Treat the leads with respect, they can be very fragile, turned my car into a V7 recently on changing the plugs.
Oil do warm, and remember, it comes out really quickly once flowing so have the collection vessel offset by some margin.
Oil do warm, and remember, it comes out really quickly once flowing so have the collection vessel offset by some margin.
Well the spark plug change was a success! 
Took my time and was very careful, but in the end it was a pretty straight forward job. Thanks mostly to the ease of access to the plugs in an i20:
The plugs that came out look pretty good to me, but they didn't have a lot of miles on them.
I think an air duster would have been useful. There was quite a bit of crap to clean from round the wires. I used a rag and a hover which wasn't too bad, but some compressed air would have been good - another reason to buy a compressor
Took my time and was very careful, but in the end it was a pretty straight forward job. Thanks mostly to the ease of access to the plugs in an i20:
The plugs that came out look pretty good to me, but they didn't have a lot of miles on them.
I think an air duster would have been useful. There was quite a bit of crap to clean from round the wires. I used a rag and a hover which wasn't too bad, but some compressed air would have been good - another reason to buy a compressor
Well done
Those plugs look OK to me & I would have no issue cleaning, gapping & reusing on one of our own cars.
ALWAYS check gaps.
I recall a programme testing young mechanics from a few years ago
One of the elements involved a plug change.
The judges had deliberately closed the gap of one BNIB plug so the electrodes were touching.
All bar one checked the gaps & spotted it. The one that didn't spent a lot of time trying to work out why the engine subsequently had a misfire.
I've used the 'rubber tube on the top of the plug' for years on plugs I can't start using my fingers. Never crossthreaded a plug.
To improve your hoover push a length of narrow plastic tubing into the crevice tool & seal with masking tape/electrical tape. Again, something I was shown a long time ago!
Those plugs look OK to me & I would have no issue cleaning, gapping & reusing on one of our own cars.
ALWAYS check gaps.
I recall a programme testing young mechanics from a few years ago
One of the elements involved a plug change.
The judges had deliberately closed the gap of one BNIB plug so the electrodes were touching.
All bar one checked the gaps & spotted it. The one that didn't spent a lot of time trying to work out why the engine subsequently had a misfire.
I've used the 'rubber tube on the top of the plug' for years on plugs I can't start using my fingers. Never crossthreaded a plug.
To improve your hoover push a length of narrow plastic tubing into the crevice tool & seal with masking tape/electrical tape. Again, something I was shown a long time ago!
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