When replacing glow plugs how do you know if they are swelled? Will they unscrew the whole way then get stuck as you try to pull them the rest of the way out, or can you tell while lossening them up with the wrench? I really don't want to break one off right at this moment (bad timing), and I have one that seems a little tight, but I am still loosening the threads and am not sure if that is just because it is tight or if I am gonna break something if I keep loosening it.

Normally with the swelling, you can still unscrew them, just can't pull them out. You can however break them off with the threads still inside the block. Even worse. Just make sure you soak them with some sort of anti-sieze prior to loosening them. Search around, there are plenty of threads on this. Good luck

Swelled glow plugs can be a PIA, but with the advent of newer style glow plugs, the swell problem isn't very common any more. Carbon can and will get a grip on the end of the glow plug and make it difficult to remove. The clearance around the tip is very small. Just be causious while removing the glow plug. Go slow, use some penetrating oil and if it starts to feel like it is stuck, go the other direction and repeat. If you get it unscrewed and still can't get it out, you can try this: First, be very carefull. With the glow plug screwed out and still in the hole, crank the engine over. Many times the compression will blow out the glow plug(like a bullet) Next choice, lock a pair of vice grips around the glow plug and start the engine. Exhaust is going to leak past the tip, so if you hold it towards the head, you will get a hammer effect going. I have used this method to remove some mildly swelled plugs. A word of caution, DO NOT REV THE ENGINE!, just let it idle. Good luck.:grd:

Swelled glow plugs can be a PIA, but with the advent of newer style glow plugs, the swell problem isn't very common any more. Carbon can and will get a grip on the end of the glow plug and make it difficult to remove. The clearance around the tip is very small. Just be causious while removing the glow plug. Go slow, use some penetrating oil and if it starts to feel like it is stuck, go the other direction and repeat. If you get it unscrewed and still can't get it out, you can try this: First, be very carefull. With the glow plug screwed out and still in the hole, crank the engine over. Many times the compression will blow out the glow plug(like a bullet) Next choice, lock a pair of vice grips around the glow plug and start the engine. Exhaust is going to leak past the tip, so if you hold it towards the head, you will get a hammer effect going. I have used this method to remove some mildly swelled plugs. A word of caution, DO NOT REV THE ENGINE!, just let it idle. Good luck.:grd:

Very nice D Cam. Never heard of this one before. I'll have to keep that in mind before next winter.

One other thing, I always use never sieze on the threads of the glow plugs when I reinstall them. Oh yeah, and my daughter just informed me that she successfully tested her glow plugs and replace 3 of them on her own! It pays to give you kids tools and lessions):h .

Sweet, thanks for the help guys, I'll try my luck this weekend....unless your daughter wants to change them out for me. :)

I snapped one of my glow plugs off this spring, almost flush with the block. Not cool.

Now I'm running around with 7 new AC Delco 60g's and one snapped off 9g.

But I have a game plan on how to get it out of there, just waiting till I get the urge to give it a try. in the mean time, I've been spraying it with Liquid Wrench every once in a while.

Saw someone use a scrap piece of aluminum bent into a U shape. This scrap was vice gripped over the exposed threads of a swollen glow plug. The glow plug cut its own threads into the aluminum and allowed for a controlled extraction of the tip through the hole.

Good info DC & MS I'll add to FAQs