[AaronO]

Over two years ago I took on the task of replacing all four glow plugs. They weren't heating on cold mornings causing cold starts. Two of the four plugs were not fully inserted, sticking up by a few mm. Another one was stuck spinning freely without coming out.

Replaced the two that were sticking out a little bit, however again they would not seat all the way in - I suspect cross threaded from a previous job. Unfortunately when trying to manipulate them, they are both now spinning freely, I think snapped on the inside. 

The last one, I just couldn't twist, even after covering it with some lubricating spray.

So, four stuck broken plugs. Funny that I have since done about 40,000mi. There is a sound of a misfire (probably compression leak or something through plug hole), and there is a lot of sludgey stuff building up around the plugs and leaking down underneath.

I'm not interested in getting the head overhauled or anything, not worth it. Should I just leave it be, or should I look into getting some special tools to drill out the plugs?

Any other suggestions would be welcome... any sort of glue that I can coat around the leaky plug holes to stop compression leak?

2009 1.6 CRDi, 160,000mi

[BrendanP]

I can't think of any glue that would withstand the heat and pressure, and to get the joint surfaces clean enough for the glue to bond in the first place would be very difficult. Your experience is why I'm hesitant to tackle the glow plugs on my partner's car. It does take longer to start from cold, but it does fire up eventually.

From some of the videos I've watched, even when you get the glow plugs out the threads on the plug appear to be 'smeared' with aluminium from the cylinder head, as though the aluminium bonds onto the plug and gets dragged out with it. It's a pity they can't or won't fit helicoil inserts into the head so that the thread is more durable.