An Easy Way To Remove Stuck Glow Plugs

[Squiggle Dog]

I've been working on my roommate's 1991 W126 350SDL and discovered that most of the glow plugs were not working. After the painful task of removing the intake manifold (yes, it must be removed on the OM603 slant 6 engines) I had easier access to removing the plugs, but once the plugs were fully unthreaded from the block, they would not pull out. Well, except for one which was the only Bosch plug in the engine. The rest were Autolites. Autolites do not have the tapered tips that the Bosch plugs have, so if they swell even a little bit, they will get stuck in the head.

I tried gripping the plugs with pliers and besides the Bosch plug, I was only able to remove one other plug by pulling very hard. I then tried a few other techniques such as using cheap wire strippers to grab the ferrule on the ends and even tried using a hammer. I also sprayed penetrating oil in through the injector holes. I then tried something different. I found a nut which fit on the body threads of a glow plug (which surprisingly seemed to be SAE threads).


I used a rotary tool and cut the nut into two pieces.


I then placed each nut half on the threads of the glow plugs since the plugs were no longer threaded into the holes, just stuck at the tips. If you run out of threads, you can place a shim of some sort (like a washer) between the nut and head.


I put a 19mm (3/4") wrench on the nut and then used a ratcheting 12mm box wrench on the glow plugs. As I turned the glow plugs, the nut would move closer to the head and then it started to push out each plug.


And out come your Autolite plugs that you thought were such a good deal. It works very well! I had them all out in about 5 minutes. So now I know an easy way to remove stuck glow plugs.

[Squiggle Dog]

The tips weren't swollen very much, but it only takes a very minute amount to get stuck, especially if there is a lot of carbon in the hole. Only one of the plugs was a Bosch. The rest were the Autolite type. The Bosch plugs have a tapered tip which resist swelling much. They also don't burn out as quickly.

Autolite on left, Bosch on right.

[ZCarFan]

Well done!  Sometimes you have to get creative.

How does that 350 compare to your 300SD in terms of power and turbo lag?  I've been curious about those despite the "rod bender" reputation.

[polymathman]

Clever!

[Squiggle Dog]

The 350SDL seemed to have decent power but started running poorly and eventually had no throttle response. I found the crankcase to be 2.5 GALLONS overfull with diesel. The lift pump seals were shot. So I am still working on the car for my roommate. The OM603 slant 6 turbo diesel is an odd engine, indeed. This is actually a 3.0 OM603 which did not have any real problems. The 3.5 OM603 which the car originally had was the rod-bender engine.