Yes, I have used the search function but seems to bring up a lot of posts with conflicting info or lot of posts about overtightened plugs etc so for a definitive answer....

How tight do you all do up your spark plugs here? NGK box shows a gasket type plug being turned 180 to 270 degrees past finger tight but I always thought 90 degrees or 1/4 turn was enough to seat it properly, and nearly a full turn is way too tight I would have thought.

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Just replaced the front set of plugs that had been in there for 51,000 kms. Fuel economy was hopeless but now about 4-5kml better per 100km around city, it was around 18l/100km.

Had old and quite ruined looking champions in there that were in very tight. Worked them out gradually by rocking them back and forth without stripping anything but took a while to do.

Now I need to work out how I can easily access the rear bank so I can change them or inspect them. Never removed the manifold etc on this car before but doesn't seem impossibly complicated.


Also why do Aus Magnas and US Diamantes use different spark plugs in same 6G74 engine?

Aus NGK plug front bank - BKR5E-11

US Diamante front - BKR6ES-11

Different temp I can see but why is that needed?

when i was working the way i got taught essentially brought it to like 215 degrees past where the washer initially contacts. we just really didnt want them to come loose i suppose.

your rear bank should be platinums, i think. unless someones done a dodgy in the past

Personally I go about 90deg past when it gets contact with the washer. That won't strip them or place excessive pressure on the thread, so I stick with 90 deg.

Rear's should be iridium's/platinum's. Only to save the manifold coming off every plug change.

*cough* TORQUE WRENCH *cough*

What torque? 25 is what the workshop manual says I think. Be a miracle if most mechanics used one to put in spark plugs though.

That's why I don't take my cars to a mechanic! lol

I thought a torque wrench would be essential to maintain the correct gap?

I thought a torque wrench would be essential to maintain the correct gap?

*not sure if sarcasm was intended there

You use a feeler gauge for that :)
You should use a torque wrench for every bolt and nut in the car technically.
But T-RT does it
(on the scale of tightness, T, RT, and RFT....)

I thought a torque wrench would be essential to maintain the correct gap?

nope, the gap is the distance between the electrodes on the plug, the torque wrench is only there to prevent over/under tightening, where the plug can break, or thread strip or not maintain cylinder pressure.

Dont forget this is a tech. sect. folks and to stay on topic.....thanks!

While we're on the topic of tight spark plugs, I've only been able to get one of the three in my front bank out (the middle one). Just to inspect to see if it/they needed replacing (not yet, still looking good). But try as I might with the other two plugs, using a plug spanner, I can't budge them at all. And I'm no 60kg weakling. I doubt if they have been touched since new. I'd rather replace all six plugs myself than have a dealer charge like a wounded bull (and yes, I know about the need to remove the inlet manifold to access the rear plugs, did it several times on my old TE, shouldn't be that much harder on a 380). Anyone got any hints? Heaps of WD40? Gentle rocking from side to side as suggested by Jordan? Hot or cold engine?

KJ.

While we're on the topic of tight spark plugs, I've only been able to get one of the three in my front bank out (the middle one). Just to inspect to see if it/they needed replacing (not yet, still looking good). But try as I might with the other two plugs, using a plug spanner, I can't budge them at all. And I'm no 60kg weakling. I doubt if they have been touched since new. I'd rather replace all six plugs myself than have a dealer charge like a wounded bull (and yes, I know about the need to remove the inlet manifold to access the rear plugs, did it several times on my old TE, shouldn't be that much harder on a 380). Anyone got any hints? Heaps of WD40? Gentle rocking from side to side as suggested by Jordan? Hot or cold engine?

KJ.

If you are having serious trouble I would personally go see a mechanic to reduce the likelihood of messing up your head which would suck.

As above. I drop a tiny amount of WD-40 down there. Are you using a breaker bar? if you are using a ratchet you may not have enough leverage.

Thanks TUFF, used a breaker bar and it did the trick. All three front bank plugs looking good, no need to replace them for another 25,000km I reckon (at 90,000km, per the service manual). They are Bosch Iridiums, same plugs front & back on a 380.

KJ.

Thanks TUFF, used a breaker bar and it did the trick. All three front bank plugs looking good, no need to replace them for another 25,000km I reckon (at 90,000km, per the service manual). They are Bosch Iridiums, same plugs front & back on a 380.

KJ.

That's cool dude. Breaker bar will always save you heaps of elbow grease in un-doing bolts. SCA had them for sale for like $20 a few months back, Got me a 2nd one they are damn handy.

Also, get yourself a range of adaptors, like 3/8" > 1"2 etc, Makes breaking 3/8" bolts a breeze with a 1/2 breaker :D

Tuffy has covered it but just a tip, if is been really tight and a pain and your scared of snapping it then crack it while the engine is hot, works well on steel bolts in alloy parts.

Tuffy has covered it but just a tip, if is been really tight and a pain and your scared of snapping it then crack it while the engine is hot, works well on steel bolts in alloy parts.

Yep, I thought this would be the case, so I cracked them with a fairly warm motor.

KJ.

There's something seriously wrong if you need to use a breaker bar to get sparkplugs out! Either the last person who put them in overtightened them, or there is adhesion between the metals of the plug and head. I'd get some antiseize grease on a new plug and run them in and out of each hole just to smoothen out the alloy. You should be able to run a plug in by hand without finding any tight spots. Look at the plugs that came out for any alloy stuck to the threads. Clean them up with a wire brush and use a smear of antiseize grease on the threads when you put them in. A simple torsion bar torque wrench is about $20, 28 Nm isn't much at all.

There's something seriously wrong if you need to use a breaker bar to get sparkplugs out! Either the last person who put them in overtightened them, or there is adhesion between the metals of the plug and head. I'd get some antiseize grease on a new plug and run them in and out of each hole just to smoothen out the alloy. You should be able to run a plug in by hand without finding any tight spots. Look at the plugs that came out for any alloy stuck to the threads. Clean them up with a wire brush and use a smear of antiseize grease on the threads when you put them in. A simple torsion bar torque wrench is about $20, 28 Nm isn't much at all.

No there is not.

If you use the rear bank of a third gen as an example, 100k's of use, plugs installed by Mits, they can get bloody tight. I have had many come in where I have had to use a breaker bar to initially crack them

breaker bar on spark plugs, wow. has anyone ever stripped the threads in the head doing this?
all this talk of seizing plugs has me worried, i might change the rear bank plugs before 100k just in case

I only use it break them free, once they are free you can use a ratchet...
Shouldnt strip the thread...

if you do it nice and controlled, no sudden jerking of the breaker bar then you should be ok. once its loose then swap to ratchet, yeah

There are some anti seize greases available - eg for the oxygen sensor - that might be useful for the plugs next time you pull them. Steel heat welding into alloy threads over 100,000 Km would be the culprit, the alloy always comes off second best, but unless a plug comes out with lumps of alloy in the thread it shouldn't be a problem. I was a bit astounded by this initially, but then I'm used to plugs that need regapping every 10,000 km. Assuming an engine life of 300,000 km, that's 30 times you pull the plugs, whereas with plugs that last 100,000 km you will only do it twice.

ok thanks, i've always used a ratchet but then i've never owned a car with platinum plugs that have such a long change interval. breaker bar on aluminum heads sounds like a recipe for disaster but i guess if you're careful it's fine. i'll do it early just in case, i've heard about the alloy-steel fusing with heat cycles and it's worrying.

for a 100000km plug i'd definitely use antiseize too. however it's interesting that the plug manufacturers themselves (eg. NGK) don't recommend using anything at all due to the special plating on their platinum/iridium plugs - i'm not going to take the risk though

Unless specified I wouldn't be putting anything on the threads, who knows what it will do over 100,000KM's?

Keep in mind they are not using the breaker bar to INSTALL the plugs, just to REMOVE them. ive taken out countless plugs, and for very tight ones the breaker bar is actually better than heaving on a short rachet handle as you have more control and are less likely to put force against the side of the plug and crack the insulation. Example, my 16yo nephew, an apprentice mechanic, was removing a plug on my brothers car, an old corolla. the plugs are near horizontal, and he was heaving up on the plug, and pushing down on it aswell to counter the force. I said " your gonna crack the plug" but he laughed and said HE was the "mechanic" and had done it many times. literally 2 seconds after, we heard a crack, and he had completely destroyed the insulator.