Siezed spark plug

Bad Ass Bob · Post by **Bad Ass Bob** » Mon Dec 03, 2007 8:32 am

ACVW BOFFINS guys i need some advise, i decided to do a service on the buses 1500 s/p motor all went well till i got to no 2 cyl the plug turned out 1/4 of a turn then stuck ,
1/ can you spray a lub of a sort ???????
2/is there a way to slowly remove with backwards and forwards movement ????????????
3/ HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Post by **fig** » Mon Dec 03, 2007 8:54 am

It's probably too late to save those threads; unless anyone else has a miracle cure, you'll probably have to force it out and repair with helicoils or an insert, both of which are problematic.

The problem here is the aluminium heads and the steel spark plugs tend to react and bond together.

To prevent this I use copperslip to lubricate the plug threads and I make a point of removing the plugs and relubing the threads at every oil change.

Post by **calooker** » Mon Dec 03, 2007 9:27 am

It could be that there is an insert in the head already that has loosened and may now be a costly repair, whichever it sounds as if the head will need repairs as fig has mentioned.

Surge · Post by **Surge** » Mon Dec 03, 2007 9:39 am

You can probably salvage the thread as long as you didn't try to FORCE IT OUT!

Get some penetrating oil (eg. 1299 in aerosol can) and spray a generous amount around the spark plug then wait an hour or two for it to seep into the threads.
First screw the plug right back in and then out till it gets tight. Apply more oil and work it back and forth about a quarter turn at a time.

I've rescued several threads like that from heads that other idiots didn't use any copper slip on.

Post by **calooker** » Mon Dec 03, 2007 10:02 am

Even if you manage to get the plug out, whichever method used it's a guarantee that the threads in the head are shot and if you just replace the plug without any form of repair it is going to pop when you least expect it.
There is no short cut on this one.

ZeroAxe · Post by **ZeroAxe** » Mon Dec 03, 2007 11:15 am

I was told what could help also is to run the engine for a short whole just enough for the heads to warm up a little and 'expand', but not so much the spark plug. HOWEVER, you then have to be extra careful not to strip the threads as the metal will be a lottle 'softer' too!

Surge · Post by **Surge** » Mon Dec 03, 2007 1:27 pm

calooker wrote:Even if you manage to get the plug out, whichever method used it's a guarantee that the threads in the head are shot

I strongly disagree - the threads will be just fine if the mechanic didn't try to force the plug out.

I've had several plugs so tight that they wouldn't turn more than 1/4 to 1/2 before seizing solid and after my tricks they came out and didn't do any damage. Not even any aluminium stuck on the plug threads.

However if someone uses force then yes they will stuff up the threads but I can't see how you can guarentee that they are stuffed without first knowing if someone tried to use force to remove the plug instead of gentle persuasion.

Post by **calooker** » Mon Dec 03, 2007 2:11 pm

Hey Surge I am not saying that you don't get lucky every now and again and will be able to refit a new plug to a plug hole that was a bitch to start off with. But if a plug hole that has been around for 35 years and had dozens of plug changes done to it over this time, considering there is only about 8mm of soft aly. Threads, the odds are stacked against the threads being 100% considering the plug as turned slightly and now decided to not come out. Penetrating fluid will get to the first 1 or 2mm of thread after that then that is where the luck sets in. Gentle persuasion is not going to get it out, if a plug gets (stuck) it's normally the initial turn that is the hardest then it tends to get easier not harder. There could be several reasons for the plug to refuse to come out, I have even found Pratley steel paste and thread maker used to try and keep a plug in place after threads have been damaged, and it doesn't take much to do damage, carbon build up on threads exposed into a combustion chamber are cooked onto the threads and are muck tougher than the aly. are big problem areas, and the reason they sit exposed is because the first 2mm of threads have been damaged over time and constant forcing.
Penetrating fluid will not break down or even reach that end of the plug.
BAB expect the worst, in my opinion the threads are going to be damaged the harder it is too take the plug out the more likely the threads are damaged due to reasons mentioned as well as cross treading.
Let us know how it goes, one way to check if the threads are ok after you remove the stubborn plug, try and fit the new plug without using a wrench, infact you should use a T-bar and nothing else as this reduces any sideways forces that are a no-no for soft ally threads, use some oil on the threads, if you cant turn it in at least a couple of times with your fingers then you know you have shit. You should always fit a plug this way it will help reduced damaged threads.
You should also not use any anti seize product on plug threads as the reduce conductivity in the circuit that is needed to produce a good strong spark, remember we are talking about a small contact area and points with a condenser that don't generate a lot of current, so every bit helps.

ZeroAxe · Post by **ZeroAxe** » Mon Dec 03, 2007 2:19 pm

calooker wrote:You should also not use any anti seize product on plug threads as the reduce conductivity in the circuit that is needed to produce a good strong spark, remember we are talking about a small contact area

Copper slip(anti seize) surely aids in earthing the spark, being such a good conductor of electricity, right?

Post by **calooker** » Mon Dec 03, 2007 2:25 pm

Copper slip is a paste/grease, I don't think it can conduct much current.

Post by **calooker** » Mon Dec 03, 2007 2:53 pm

The plugs or anthing with thread needs to be torqued to a specific spec, any aditive to the threads will lead to a false torque reading, any torque rating is speced on the fact that threads are clean and free of any form of addative.
Copper slip is for use on brake pads. And if I remember it is copper oxide and not actual copper, I am no metals expert.

ZeroAxe · Post by **ZeroAxe** » Mon Dec 03, 2007 3:12 pm

All ears and eyes...... keep teaching..... erm.... talking

Bad Ass Bob · Post by **Bad Ass Bob** » Tue Dec 04, 2007 7:39 am

Well guys with all that fuss and bother Q20 and a 1/4 " drive socket i got the offending plug out seams it was build up on the plug so im gonna run a tap through the hole blow clean and it should be ok ,

so thanks to all those concerned, all the ideas together solved my problem,!!!!!!!!!!!!!!!!!!!!!!!!!!!B.A.B