I'm curious about your recommendation of Hylomar, where have you seen it used for glow plugs? I can't seem to find much information on it other than from your recommendation. There's a few different varieties of the brand. And what other products could be used as a substitute perhaps? How important is it to employ a compound on the shaft as opposed to leaving it bare? I saw a video of a guy using liquimoly (3381) ceramic based anti-seize/grease on the shaft. Thoughts?

I hope this reaches you I know this is an older thread.

Yeah, old thread. Sorry if anyone is bothered but it's good to have all of the pertinent info in the same place.

pimpernell's quoted link is great! It also shows loosening torques (incorrectly labeled, for some reason). The idea is to prevent breaking the glow plug when removing. However uncommon this may be, it would be a big problem to fix I would imagine.

The doc says "ONLY remove and fit glow plugs using a torque wrench."

MAXIMUM removal torques are given as follows on page 15 (consider starting lower):

M8 - 20 Nm
M9 - 22 Nm
M10 - 35 Nm
M12 - 45 Nm

If they stick when removing, i.e., requiring that you exceed the removal torque values, apply synthetic oil (pb blaster like product?) and leave it to act, possibly overnight. Then warm up the engine. Then try again. Don't exceed the removal torques - repeat the above as required.

Tightening torques* for installation:

M8 - 10 Nm
M9 - 12 Nm
M10 - 15 Nm
M12 - 22 Nm

and for installing the electrical contact nut:

M4 2 Nm
M5 3 Nm

*But what about the money question? Should the threads be dry? Use AntiSeize? Grease? Not surprisingly, even this 16 page article is contradictory!

Statement against (install dry) page 13:

"Tighten plug with suitable torque socket wrench. Strictly comply with the specified torque (refer to specifications of the car manufacturers). Do not oil or grease the thread"

Statement for (use grease) page 15:

Last quote from the article - After reaming, "Before installing the glow plugs, grease the shaft and thread areas with GK grease (GFK01 – 0 890 300 034)"

So, it appears that you can just do whatever you think is going to work best.

One more point: From a cursory google search, the internet consensus seems to be that if you use anti-seize or grease on any threads that you should reduce the installation torque by 25-30% due to the addition of the lubricant (see one reference regarding this at the FCP Euro Blog) [For some reason that is unknown to me, when I add the link it has *s instead of "*******". If you replace the *s with the text in the URL bar after clicking, the link will work. I will ask for help and edit as needed.]

Cheers!

__________________
_____________________________________

Chris_87_300D
1987 300D - 415,000+ miles
1999 E320 - 220,000+ miles
2008 SL55
2019 Sprinter Diesel 4x4

The point about reducing torque is I think the most important. Greasing threads with any lubricant or antiseize can lead to overtorque.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)

In 18 years of being a diesel mechanic I always used the never-sneeze from a regular auto parts chain store on glow plugs and exhaust system nuts and bolts with no ill effects.

__________________
84 300D, 82 Volvo 244Gl Diesel

Couldn't get the link to work, but found this by searching ' beru federalmogul files

Beru recommends:

Always grease the glow plug shaft and thread when changing glow plugs.

Glow plug mounting grease GKF01
■ prevents thread corrosion and therefore stuck glow plugs
■ prevents the penetration of water
■ facilities glow plug replacement

Also, an old thread has a few additional comments

BERU Glow Plug assembly grease