Blow it, it won’t shift
QI decided to check the glowplugs in our BMC 1.5. Two were okay, one glowed only halfway up, and the other one snapped off and left the glowing end stuck in the cylinder head. I can just get a pair of long nosed pliers on it, but cannot budge it. My only thought is to spray some oven cleaner around it and try turning the engine over and see if the compression will move it. Do you have any other suggestions?
MARK BROWN, via email
ATONY REPLIES: Oven cleaner might work, but as the cleaner will have to penetrate several mm of baked hard carbon, I rather doubt it. To do the job with 100% likelihood of success you should take the cylinder head off and that injector out, so you can blow and shake any swarf out of the pre-combustion chamber. If you will settle for a 98% chance of success, leave the head on and remove the injector plus the ‘inverted top hat’ heat shield from below the injector (a new copper washer should be refitted under the heat shield upon reassembly). If a 95% chance of success is okay, simply remove the injector (replace the atomisation washer). If you will settle for a 90% likelihood of total success, leave the injector in. (The risk is that the end of the broken tip might embed itself in the piston, or get stuck under a valve – neither has happened to me yet.)
Get a drill bit no more than 0.5mm larger than the glowplug tip (I think it’s 7/64in) in a hand or low power battery drill, grease the tip of the bit and drill the tip out for a few moments. Wipe the grease and swarf off the tip of the drill and re-grease. Drill again for a few moments and repeat until you feel the drill break through into the pre-combustion chamber. Use the same drill to drill the carbon from all of the other glowplug holes. Protect your eyes and spin the engine on the starter to blow any swarf and loose carbon out of the holes.
Coat the tip and thread of all the plugs with copper grease before refitting. To avoid this problem again I would suggest that you repeat at three-yearly intervals.