I need to replace some glow plugs in the 1986 300SDL. Since I don't know the history of the plugs I figure I'll just replace all six. Do I need to remove the intake manifold or is it possible to do all six gp's without removing it? Thanks.

I'll suggest that you test them first. You can pull the plug and check resistance of each with a multimeter. If they are around 1 ohm they're fine.

That way, you only replace what's broke!

I did my #4 and #6 without pulling manifold. It took a few different socket extensions and a bit of patience, but overall was faster than removing the manifold.

Best Regards,
Jim

Tested them and all but two were around 1.2ohms. OK, here's the million-dollar question, Jim. How do you count the glowplugs on the engine? Is the front-most of the car #1, and does it go back sequentially?

You are correct! 12345 and 6 being the last next to the firewall.

I'll also add that I replaced #3 without removing anything. Haven't tried the others. I used a 1/4" drive with univeral joint and extensions. I also found it handy to have a extension magnet if you slip and drop a socket etc.

Thanks for the help, gents! I'm off to the dealer to get some gp's. We got snow, but it's a clear, sunny day. Time to have some fun.

You could buy Bosch plugs from Autozone for probably about half the price. I bet the plugs you get from the dealer either say Bosch or Beru on them.

Some people have figured out how to change them all without pulling the manifold. I couldn't so I just yanked the thing. I wanted to clean all of the egr tar out anyway.

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I did get #6 and #5 done, but after playing since 11 this morning I couldn't get the #2 gp out. Its nut must've been rusted onto that threaded shaft because it all came out, leaving me with the gp body. I could get a socket in there with a u-joint but it wouldn't budge. I tried going in other ways but no deal. #3 looks even worse of a job. I also noticed the manifold is slightly leaking so it's time for a new gasket on there. So, for the glow plugs and the manifold I admit defeat. I'm taking her in tomorrow AM and let my mechanic do it. Some jobs are worth paying someone else to do it. I try to do what I can on my cars and would rather have it that way. Guess I'll drown my sorrowful defeat with a few brewskies and hot wings tonight.

ps, forgot to say thanks Jim for the info. I actually tried the local Autozone and Napa but they were out. BTW, Pep Boys said they don't carry gp's for cars anymore.