Has anyone stripped or cross threaded a spark plug hole ? Can it be re- threaded without removing the head ? it can happen that you cross thread when re fitting a plug then when it's removed again the thread will no longer allow another spark plug to hold tight...
Technical Stripped spark plug hole thread...
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Stripped spark plug hole thread...
They can be re threaded without removing the head.
the spark plugs presented themselves easily as it's a vertical in line 4 ..Not so easy with a V4 or worse still flat 4. No mention of a vacuum cleaner to remove any metal particles
The Panda Nut
Nutty about Pandas Infected by Panda virus and OPD
Yes and yes. Easy to cross thread. My garage did mine for me, thread cleaned and it was OK. He said he could replace the thread if necessary. In my case the cost was minimal.
Spark plugs, simple, quick, easy | FIAT Panda (Mk3)
Unplug the lead Unscrew the plug Screw the new ones in Torque up Plug the leads back on and drive off That's how it should go and often does Most of the problems are avoidable Don't change the plugs while it's raining Don't leave the plugs in past 100,000 miles Don't over torque Don't under...
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you had yours re - threaded ? I've not changed one of my plugs for over three years as I'm sure it wont go back in.. I didn't see the guy hoover out the inside of the cylinder head
Don't overly worry about the metal swarf
Start the engine with the plug out, blows the majority out
The rest will either pass the exhaust valve or get burnt off
There not big enough or hard enough to cause any damage
Start the engine with the plug out, blows the majority out
The rest will either pass the exhaust valve or get burnt off
There not big enough or hard enough to cause any damage
Is yours actully damaged, or are you not confident they will come out okay
The Panda Nut
Nutty about Pandas Infected by Panda virus and OPD
My guy said he used a mirror to view the thread and then set about clearing it and pulling the thread back before very carefully putting the plug back bit at a time. Mine was cross threaded by a previous owner and I replicated the mistake and by the sounds of it like you lacked the courage to really have a go. I have a back problem too which means that spending an hour bent over to do this was not a reality. He assured me it was not difficult to get the new plug back in correctly. Just very fiddly, but he is a very good mechanic and engineer so whats easy for himwould be more taxing for me. Its always best to start plugs by hand, especially when they go in at an angle and its difficult to judge it. With the Panda I feel its best to change one at a time so you can judge the correct angle of insertion by the second plug of each pair. My garage man said he could have managed to put a thread insert in the head if required without head removal but he was really glad he didnt need to. I feel that actually stripping the thread is unlikely and hope youwould be able to carefully get a plug to follow the correct thread. The problem then is to remember the weakness next time and be ultra careful. That is where I went wrong.
It would come out but I'm not sure I could screw a new one back in and that it would hold tight and not be blown out
What makes you think this
Are the thread damaged
Modem genuine plugs are normally platted.and come.out fine after 3 years
I think too a drop or two of oil on the plug thread would help
They should go in dry if you are going to torque them up using a torque wrench
Oiled will over tighten them and risks damage
They are coated, no need to oil read link in post 5 should explain everything
Start them by hand they are at an angle
Back in the days of cast iron heads this was not a problem you came across that often. Then, for many good reasons, ally heads came about which are a much softer metal and damage to plug hole threads became more common. The best advice I was ever given is to locate and screw the plug fully home by hand, only using a ratchet handle/tommy bar/torque wrench or whatever for final tightening and if it's reluctantly to screw in then it gives you the chance to "regroup" before irreparable damage is done. Same thinking applies when screwing tube nuts into wheel cylinders etc?
Anyway when you do run into this problem, unless the perpetrator has been very ham fisted, you may well be able to quite cheaply remedy the situation with a simple home made tool. Most plugs these days have a quite long threaded portion, unlike my small engine plugs which have maybe half a dozen turns of thread. What this means is that if the plug is cross threaded then, unless the installer is really stupid, the plug will jam up by the time it gets in for two or three turns. This leaves more than enough undamaged threads deeper in the hole to adequately secure the plug. All that's needed is to correct the damaged threads. When I first started out I was shown how to make a "thread chaser" from an old plug. I'll now include a picture but I' going to close here and start again as this is getting to be a very big post.
Anyway when you do run into this problem, unless the perpetrator has been very ham fisted, you may well be able to quite cheaply remedy the situation with a simple home made tool. Most plugs these days have a quite long threaded portion, unlike my small engine plugs which have maybe half a dozen turns of thread. What this means is that if the plug is cross threaded then, unless the installer is really stupid, the plug will jam up by the time it gets in for two or three turns. This leaves more than enough undamaged threads deeper in the hole to adequately secure the plug. All that's needed is to correct the damaged threads. When I first started out I was shown how to make a "thread chaser" from an old plug. I'll now include a picture but I' going to close here and start again as this is getting to be a very big post.
Should be necessary if you remove the plugs and start the new by hand
Ok, I'm back. Here's one of the tools I made.
It's long because I made this one for the deeply recessed plugs on the Peugeot 504. But actually it's a help being long because it helps with lining it up - as long as there's access of course.
The "business" end is an old plug with the ceramic broken out and slots run down it with a hacksaw - two blades together to form a wider slot - it works just like a tap and especially well on the softer aluminium heads.
This is an easy tool to make and I have several to suit different sizes.
Of course if the damage is really severe or the plug is short reach, like my horticultural/lawn mower engines, then you will need to rethread it - most likely with a thread insert.
Lawnmowers/cultivators/and the like, with 14mm short reach plugs, are very commonly damaged - short reach and ham fisted gardeners virtually guarantee it! For this I have a genuine helicoil kit
Which I got cheaply at an auto jumble many many moons ago (Portobello town hall) and I've used it quite a lot on old Briggs/Tecumseh side valve type engines which have very short reach plugs so can be stripped just if you're a bit heavy handed. With these I'll often have the head off anyway to swarf isn't a big problem but it is more of a problem if doing it with the head in place on the block. In these situations I will position the piston at TDC , drill out the hole with the drill and I have an air gun with a long reach which I can get right inside the combustion chamber and give a really good blow out. Then I coat the tap with high melting point grease and cut the thread in several stages, frequently backing it out of the hole and cleaning the trapped swarf and grease before applying more grease and repeating. In this way most of the swarf is trapped in the grease but I still give it another good blow out before installing the insert. The two taps on the left are a roughing tap at the bottom and a finishing one on top. The one to the right is a 14mm which can be used for thread correction if I think I can get away without needing an insert. The thing in the middle is an installing tool which compresses the wire type insert and makes installation much easier, especially getting it started in the thread.
One of the biggest problems with working in situ is access. This often is less than ideal and can make the possibility of errors during the drilling, tapping and installation more of a problem. If I was starting from scratch I'd buy one of the all in one installation kits shown in one of the earlier posts. If you've looked at the video you'll have seen how they have a starting thread which is the same diameter and thread as the original plug hole and then a bigger diameter which cuts the thread for the insert. The smaller diameter lets you get it started off in line with the hole more easily and it then "drags" the larger diameter in after it. Much easier and no drill needed. Turns it into a "one shot"operation.
It's long because I made this one for the deeply recessed plugs on the Peugeot 504. But actually it's a help being long because it helps with lining it up - as long as there's access of course.
The "business" end is an old plug with the ceramic broken out and slots run down it with a hacksaw - two blades together to form a wider slot - it works just like a tap and especially well on the softer aluminium heads.
This is an easy tool to make and I have several to suit different sizes.
Of course if the damage is really severe or the plug is short reach, like my horticultural/lawn mower engines, then you will need to rethread it - most likely with a thread insert.
Lawnmowers/cultivators/and the like, with 14mm short reach plugs, are very commonly damaged - short reach and ham fisted gardeners virtually guarantee it! For this I have a genuine helicoil kit
Which I got cheaply at an auto jumble many many moons ago (Portobello town hall) and I've used it quite a lot on old Briggs/Tecumseh side valve type engines which have very short reach plugs so can be stripped just if you're a bit heavy handed. With these I'll often have the head off anyway to swarf isn't a big problem but it is more of a problem if doing it with the head in place on the block. In these situations I will position the piston at TDC , drill out the hole with the drill and I have an air gun with a long reach which I can get right inside the combustion chamber and give a really good blow out. Then I coat the tap with high melting point grease and cut the thread in several stages, frequently backing it out of the hole and cleaning the trapped swarf and grease before applying more grease and repeating. In this way most of the swarf is trapped in the grease but I still give it another good blow out before installing the insert. The two taps on the left are a roughing tap at the bottom and a finishing one on top. The one to the right is a 14mm which can be used for thread correction if I think I can get away without needing an insert. The thing in the middle is an installing tool which compresses the wire type insert and makes installation much easier, especially getting it started in the thread.
One of the biggest problems with working in situ is access. This often is less than ideal and can make the possibility of errors during the drilling, tapping and installation more of a problem. If I was starting from scratch I'd buy one of the all in one installation kits shown in one of the earlier posts. If you've looked at the video you'll have seen how they have a starting thread which is the same diameter and thread as the original plug hole and then a bigger diameter which cuts the thread for the insert. The smaller diameter lets you get it started off in line with the hole more easily and it then "drags" the larger diameter in after it. Much easier and no drill needed. Turns it into a "one shot"operation.
Yes, I've seen these advertised. What a brilliant Idea. If I was younger and doing more, I'd be buying one of those immediately!
The power of the internet
Expanding taps were patented in 1870
If you don't know they exist, you don't know to look for, ask for them, I guess the back tap became popular with the rise of aluminium heads 1990s
Looking at the prices £5 upwards, Sealy ones are around £15
Thanks for the heads up. That's very affordable. I'll keep it in mind - don't have an immediate use for one right at the minute.
Whenever I've put in a plug I would hand tighten then another whole turn to turn and half...
