Seized spark plug

[elwesso]

Alright, another member of another forum (caddy forum) had a cadillac catera and has recently sold it...

Anyway, he picked up a 90 Q with 189k... He said that the car had the spark plugs replaced at 176k..... However he said the no 8 spark plug was not replaced because it was seized in place..... Dont worry Ive already warned him about the guides and ownership expenses..

Anyway, Id like to konw what experiences members have had with seized spark plugs... Ill assume that the plugs were original at 176k but maybe not.. If it were me I would throw a breaker bar on my ratchet and keep pulling... I want to try and fix this for the guy but I dont if I want to mess with it... Stripping out a plug on the head would be BAD NEWS..... Considering what its like to get at that damn plug it may just be they didnt try real hard to get it out and what not... I had also thought about using some of that penetrating lubricant stuff (I think its called PB or something) and doing that but Im not sure.....

[3Q Jay]

I'd try it with the cyl head warm [not too hot], and take advantage of the higher cte of aluminum. I've also had success with 'impact' type ccw hand torquing. only downside i see on penetrating oil is if it runs into the cyl upon removal it could get past the rings and into the oil proper. imo better that than breaking the plug. speaking of which, you know there is that risk that you will crack the ceramic, and then you're reallly committed.

[DAEDALUS]

PB Blaster. Usually removing the plugs isn't a problem since the head's aluminum. It should be a little easier if the engine is warmed up real good since aluminum expands more than steel does--the hole will grow more than the plug when heated up. Well, actually, I guess that assumes the plug and the head are the same temp. Warm it up, shut it off and then let it sit for 5-10 minutes.I don't think I've ever seen aluminum heads lose threads *unless* the plug was cross-threaded when it was installed. This might explain the difficulty with removing it. Careful--if this is the case and it does strip out, you'll be way far up hsit creek. I wouldn't even want to try to install a helicoil that deep in a head and vacuum out all the little shavings. Give it a try I guess, with a disclaimer up front, and don't force it.

[maxnix]

if the engine is warmed up real good since aluminum expands more than steel does--the hole will grow more than the plug when heated up. Well, actually, I guess that assumes the plug and the head are the same temp. Warm it up, shut it off and then let it sit for 5-10 minutes.

No, no, mon ami, the threads will be tighter if there is any expansion at all. Heat my loosen some heavyweight gunk on the threads, but the orifice would have to shrink for it to be looser.

[DAEDALUS]

The hole would have to shrink to be looser? Please explain.

[nab911]

LOL Please someone chime in on this. We had trouble like this a week ago trying to pull my friends flywheel off. The bolts were torqued well past 200 lbs and we could not get them out to save our lives. Then we all thought about the torching the bolt idea and then starts the 3 in the morning arguing about physics ****. Heat expands EVERYTHING but h20. So why would torching a bolt loosen. We argued forever but when my friend started grinding the bolts. They became loose enough to use vise grips to unscrew them. Someone please explain this and elwesso, use something to heat up the plugs and pull them out, i cant explain why but heat works .

[nab911]

The hole would have to shrink to be looser? Please explain.

And he means the head shrink making the hole bigger.

[DAEDALUS]

Maybe there's a hidden explanation here I'm not catching. The head shrinking will make the hole bigger?

[maxnix]

Yes, if heat expands the metal, the hole will shrink, not enlarge. If the metal contracts when cooler, then the hole will enlarge.

[nab911]

I understand what your saying maxnix, but against all physics laws, heating a bolt/plug whatever, will loosen it. I want someone to explain this from a physics point of view because the heat should lock the thing in, but it WILL loosen it.

[DAEDALUS]

Incorrect. The head is not confined. It is not expanding toward the holes in it. The material is isotropic. Heated, it will expand outward in all directions. The hole will get bigger.

[Q451990]

I have seen plugs seize in an aluminum head. My parent's 1982 Mazda 626 had this problem to the extent that my dad had to re-tap the threads when it was all over with. I often wonder how many peices of aluminum got down in the pistion and scored the walls. I believe the steel and aluminum have a chemical reaction that causes the seizing.

Because of that experience, I have never installed spark plugs without antiseize compound (available at most any auto parts store).

In this case all you can do is try to force the plug out using all of the recommendations here... Then deal with the thread issues if they happen.

Heath

[maxnix]

Heated, it will expand outward in all directions. The hole will get bigger.

If it expands in all directions, what keeps it from expanding into the spark plug orifice other than the spark plug itself?

[DAEDALUS]

The constraints simply aren't there. The hole moves with the material around it. Try this:Picture a square plate of steel. Draw a circle on it with a pen. Then heat the plate. Does the circle get bigger or smaller?Now picure the same steel plate with a hole cut through it, and a disk--same material and exactly the same size as the hole--placed in the hole. Heat them both up evenly. Will the disk be larger or smaller than the hole? They will be exactly the same size.Consider that when replacing valve stem guides (which are larger than the holes they go into), the FSM instructs you to first heat up the head in oil to 200* before pressing them in place. Why do they say to do this?

[DAEDALUS]

http://www.physics.odu.edu/~hy...6.ppt

[maxnix]

The constraints simply aren't there. The hole moves with the material around it.

Then if the surface tension of the opening prevents contraction of the orfice, then the metal does not expand in all directions. Can't have it both ways.

Consider that when replacing valve stem guides (which are larger than the holes they go into), the FSM instructs you to first heat up the head in oil to 200* before pressing them in place. Why do they say to do this?

Lubrication?

[DAEDALUS]

Then if the surface tension of the opening prevents contraction of the orfice, then the metal does not expand in all directions. Can't have it both ways. Lubrication?

Surface tension? What are you talking about? The metal is trying to avoid having any stresses in it--by expanding. If by "both ways" you mean the plate expanding in all directions and having a larger hole in the plate, then yes, I can have it both ways. It's not my fault. That's just the way it is. If a college physics departmemt presentation does not convince you, I don't think I can either.Do you really think completely submerging an engine head in a vat of oil is required to lubricate the valve stem guides? Why not throw the guides in a vat of oil?

[squeefoo]

I believe the steel and aluminum have a chemical reaction that causes the seizing.Heath

Yes Of course I forget the proper term (bimetallic corrosion?), AL is a trivalent positive ion, a strong oxidixer (Alkaline). A big problem in casting complex parts, such as valve bodies, where the heat accelerates the process in the die, ripping out the ribbing. I filed a patent on a cure for this but the "Experts" won't listen to someone w/out experience in that field. GM did but then they went on strike, and no more experimentation.

WES Try some dry ice on the plug when the head is warm, just slide some onto the plug. The holes bigger and the plug is smaller.

[msscomm]

He said that the car had the spark plugs replaced at 176k..... However he said the no 8 spark plug was not replaced because it was seized in place . . . Ill assume that the plugs were original at 176k but maybe not.. If it were me I would throw a breaker bar on my ratchet and keep pulling... I want to try and fix this for the guy but I dont if I want to mess with it... Stripping out a plug on the head would be BAD NEWS . . .

The old standby has always been torch the head to expand her, then wrench out the plug - NOT GONNA HAPPEN w/the deep set plugs on a Q head w/o major disassembly - if you insist on the thermal shtick methodology - bimetallic expansion games can be tried w/warmed head and slipping a socket from the freezer over her trying to get the chill to shrink the plug and cause a microscopic break between the threads and the corrosion holding everything together -

Get a can of PB Blaster. Spray it on and wait several cycles ......should break free with ease....Unless some person of relatively high IQ cross threaded it!!! Go slow and easy! Rock it back and forth, trying to get a 1/4 turn extra each time, and going all the way back in each time. Even better than the Parker Brothers (PB) "Blaster" penetrant, which is very good, you might also try Kroil - a product that seems to find a lot of favor in the aircraft industry which uses a lot of aluminum. I have had no luck finding Kroil at any parts places, but you can order direct - they have a web site - do a search for Kroil. (Check w/your local reloaders)

Also - take note of the suggestion to use the penetrant several times over the period of several days and through several heatup/cool down cycles. Don't bother with stuff like WD40 and the usual stuff on the discount auto parts stores shelves - useless for serious work like this. And when removing, do the out 1/4, back in and out a little further. etc. routine, spraying additional penetrant each cycle. – Don’t worry man - absolutely no hydrolock potential if you drop a cloth/absorbent material around the plug threads to mop up once you get her broken and finally moving.

a SAD REALITY is threads on both the heads and the plugs can literally gall and weld themselves together if just left "to their own" for 100K plus - and you're approaching double that - but cheer up - I have NEVER seen a failed removal attempt w/a pneumatic impact gun (if they weren't cross threaded) - but I’m no pro

Do the typical minimal damage first method - run down the torque setting on a pneumatic impact wrench and let modern mechanics work for you - next, a couple of heat/cool cycles using penetrating oil, then go with a breaker bar, and a bit of impact adjustment (tap her w/a hammer on the socket/extension sitting cleanly on the plug) - next is a cheater pipe (along w/paid up insurance), and then we get to the serious who gives it up first - you or the threads - Rip that Sum***** out and ta hell w/the consequences - although no damn fun, Helicoiling an AL head can be done

[elwesso]

Thanks Mike... I appreciate the response, this thread has turned into a physics lesson.....

I will discuss with him the risks involved and we'll give it a shot.....

I like the idea of an impact wrench, but there inlies the problem: theres not enough room! no 8 cylidner, the WORSE place for a seized plug!!!!

[squeefoo]

WES: This requires finesse. If this takes an hour or two to remove the the plug,( if I remember correctly to remove the head book is 33 hrs.?) obviously anything less is worth it. It's to everyones benefit. Don't use an inpact on the head, I know it won't fit, (we gotta talk him down people!), just put down the impact slowly........and step away, nobody wants to get hurt here. We're all here together. ( ha? ) Just a 1/32 of a turn at a time works. The gasket may have brinnelled into the head rendering any rust solvent/lube a moot point, until its moved just a little to unseat. Now it's just to shear the dirt/ carbon/ welded together aluminum oxide/ ferrous oxide asperities that are in there, that should let loose before the thread torque does. Don't go toooo long w/the bar you can't it feel as good, hot/cold to break it loose, then some penetrant once a thread is exposed. Watch out for the torque spike !!! Hope this helps.

[texasoil]

Putting in a heilcoil, should it strip, is not as bad as you might imagine. Grease on the drill and tap, etc to hold chips, work slowly, blow out the cylinder with air jet from tubing on an air hose dropped into the cylinder.

This type of problem all the time on old VW's.