How to release a seized spark plug in your aircooled VW engine

When you're taking out the spark plugs to check their gaps or replace them with new ones it's very important not to force them if one is stuck. Forcing it can damage the thread in the engine the plug screws down in to, and that's a lot of work to fix, even if you 'just' bore out the broken thread and put in a some replacement thread inserts. Yeah, that does sound really simple doesn't it!

If the plug won't unscrew or is very sticky, spray oil down the barrel so it collects around the plug, then leave it to soak in down the thread. Leave it as long as you can, but if you're the impatient sort give it ten minutes to half an hour. Give the plug a gentle tap on the end, then try tightening it slightly before trying to unscrew it again. This will hopefully cause the rust or gunk that's jamming the plug in to crack, giving it a chance to unscrew.

Again, if the plug is still stuck, don't force it. Soak it with oil again. If possible, run the engine a while to warm it up, then spray in the oil again and leave it to cool - the heat should help work the oil in to the jammed thread. One method I've seen with jammed pistons is to warm the oil rather than the engine before you pour it in - don't try this if it's a spray can of WD40. Losing your hand when the can explodes is going to seriously slow down the fixing of your car.

Eventually, the damn thing should come out. When putting a new plug back in, you might want to think about putting some high-heat resistant lubricant around the thread of the new plug. I've never needed to use any lubricant on plugs on any of the cars I've had, aircooled or otherwise, but if you've had a very sticky plug it might be worth it. In this case it's also a good idea to unscrew and screw back in the plugs every few weeks, just to make sure they aren't jamming up again.