W123 300d Glowplugs problem

[32370]

I have a 1976 W123 300D I bought 2 years ago as a hobby/DIY car. It is fitted with the old loop style glowplugs. I decided to change these for the pencil type plugs- a common conversion. I patiently removed the plugs one by one leaving the middle, hardest to get at, till last. All the plugs were very tight. the last one to remove of course turned out to be a problem. With about two threads left to go before removal, the outer metal part of the plug separated from the inner ceramic core and started to rotate seperately. The outer case of the plug will now turn by hand but the inner core is stuck solid so the whole thing will not come out of the cylinder head. I have read in the Mercedesshop forum that this is not that uncommon. Does anyone reading this have experience of the problem and has had it sorted by a garage. It is a fairly easy engineering job, you just need the right tools. ie a suitable slide hammer and a tap to repair the last two threads if necessary. What I don't want is a dealer telling me the head has got to come off!

 

[mebobster]

hi, exactly the same thing happened to me on my E300TD. you could try getting a nut that fits around the core with the right thread, and try spot welding it on, and attempt at removing it with the correct spanner. this is a good way of doing it, and it has helped other mechanics i know. unfortunately in my case, it didnt! and i had to remove the head. by the way, if its a DIY/hobby, why not add a head gasket to the work! sorry, only joking. i wasnt too happy when i had to get the head removed on mine, but at least i know its got a new head gasket on...good luck.

 

[32370]

As I get older I get clumsier, so I won't be taking the head off. I am about to visit a few local recommended mechanics/diesel agents to see what response I get. Thanks for your reply. Is there any one else out there suffered the same problem?

 

[Xtractorfan]

Yes same problem tho on a mondeo , and we are blessed in the fact that we have a local mobile engineering guy who came along and welded a nut to it as above and removed it using a sliding hammer and a pair of vise grips..
#The other thing you could do replace all the other plugs, tie a piece of wire to the errant plug ...so it wont hit the bonnet... and close the bonnet and start the engine..it has been done and it has worked

 

[32370]

W123 Glowplugs

Good news. It's out! Thanks for the replies which reinforced the options I had considered.
Thanks also to Andy Gayle for taking the time to reply to the email I sent to him, and to Lee at Autok of Worcester who I visited, and who offered his professional advice also. In the end I bit the bullet and used a piece of wood behind the glowplug to protect the injection pump and started the engine briefly. Although the plug appeared not to have moved, the outer casing now moved completely freely and using some mole grip type pliers I was able to get sufficient force on the plug to pull it out, much to my relief. All I can say is that on older cars, this one is 32 years old, even relatively easy DIY jobs can be fraught with unexpected difficulties, so never take anything for granted. My problems were compounded by my having used the car as a testbed for pure vegetable oil consumption, more from a environmental viewpoint than a cost saving perspective, the resulting carbon deposits having been a product of this extended trial. The engine could only be started with the aid of starting spray injected through the air intake with the glowplugs disconnected to prevent destruction of the engine. The car is now back in service having had a good run down the motorway on a tank of diesel with injector cleaning additives in it. I had replaced the original series wired Loop style bosch glowplugs with the bosch duratherm parallel wired pencil style glowplugs, and can confirm the conversion works using the original glowplug relay should anyone else be thinking of carrying out the conversion.