Removing a Broken Off Glow Plug

Not easy by any means. Options and ways to prevent it are listed here.

This is not the first time we have received an email like this one. "As you can see (in the included emailed photos) the broken pencil glow plug broke off from the threads and is sticking out around 1/4 inch. There not a lot of room to work. I tried using an easy out with no luck. What should I do?"

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Problem & Solution

Common among these chassis:

W116
W123
W124
W126
W140
W201
W210

Kent has three recommendations.

1. Take it to a automotive machine shop to see if they can drill and tap it out. If it broke due to corrosion do NOT try to use an easy out. If you break the easy out then you will have a much worse problem.

2. Take the cylinder head off. This is a lot of work and only should be done if the shop can not do it with the head on.

3. Just leave it in there and drive it (provided it is still sealed).  This is not ideal, but if your other glow plugs are strong the engine will start without one glow plug. Over time you will start to build up carbon in the pre-chamber ( 30,000 to 50,000 miles) and you will have to get it out and clean the pre chamber or the engine will start running rough due to poor fuel combustion.

NOTE: This is a good example of why you want to ream the carbon out of the prechambers on an old diesel engine at least every 60,000 miles. It is also a good case for using a very slight amount of antiseize compond when you install glow plugs. Also, be very careful how much you tighten them. They should be tight like a spark plug - but not strong armed tight!