I'm a firm believer in WD40 and a cup of coffee or two while it has time to penetrate. Never tried it on spark plugs but it's worked for me on everything else I've tried.
I can't see quite how it would soak in *but* it's all I can think of too so I'll give it a go!
I've been treating some bike exhaust studs in this way ready for the weekend.
Not going to sweat to much about this. HJ's Mondeo with 107k at 2 grand at auction seems like a barg.
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Parp, Parp!
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The saltwater you mentioned may have something to do with the rust-I always WD40 (the single best invention for car/boat maintainance?) the exposed part of the plugs when replaced as the saline road conditions in England can murder unprotected engine parts.
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Toad
No, I don't understand it either but a combination of capillary action and/or gravity has always worked for me in the past - last time was last weekend with a corroded screw in the caravan water heater.
Terry
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Toad No, I don't understand it either but a combination of capillary action and/or gravity has always worked for me in the past
Ditto! I've used it on countless bolts which in theory ought to be as watertight as a plug!
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Parp, Parp!
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I have used WD40 but for really BAD aluminium to iron corrosion, Vinegar is better.
I used it to move the thermostat housing on a Mark3 (1981) Jaguar XJ6. The thermostat had jammed shut (steam!) and one of the studs sheared. The other 2 were solid. I removed the entire manifold, and soaked it in vineagr. then I went away for the weekend.
Worked a treat: vinegar dissoves oxides of aluminium/iron...
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Oddly enough, Madf, I got the other plugs out literally a couple of weeks ago. (Maybe this should be on the preminition thread!)
I soaked in Plus Gas, BUT, and this is the strange bit. The stuck ones were now no more than finger tight. In May me and another guy had a go and agreed they were too 'springy' to risk. (15 inch breaker bar was 'springing'). Car was cold when they seemed loose, that was the only difference.
Will remeber the vinegar trick.
None have split since May but all are rusty.
Car is up for MOT soon so may have to go.
Over 25k and 3 years. Not bad.
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These are my own opinions, and not necessarily those of all Toads.
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Threads (unless tapered) are not designed to be sealed, the seal is the the compressed washer or flat mating surfaces. From memory I believe most sparking plugs use parallel threads, notable exceptions being the Ford Fiesta Fisaco.
This will then allow combustion products up the thread, presumably causing the corrosion that locks the thread tight.
How WD40 or sililar will seep down I do not know. Any comments?
pmh (was peter)
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Peter
You are right that the thread on a spark plug does not form the seal. However all spark plugs use parallel threads, even the Valencia engined Fords. These engines (and some others) do however use spark plugs with a tapered seat for sealing (not a tapered thread), rather than the flat seat/washer combination.
Regards
John S
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Never come across a seized plug, but we have had some tight ones!
I know what the Valencia Ford ones can be like.......glad we;re not a Ford Dealership!!
Try removing the offending plug with the engine red-hot, this sometimes helps.
If all else fails, a 3/4" drive impact wrench usually does the trick ;)
MG-Rover Problems? forums.mg-rover.org/
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Another alternative is Coca-Cola!
This is often used by professional caterers to restore stained cutlery which is soaked overnight in the stuff and emerges like new.
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Better go out and get some of the REAL thing!
MG-Rover Problems? forums.mg-rover.org/
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