Glow plugs: Should I use a reamer to clean out the carbon?
 

Hey,
I'm about to change the glow plugs on my 300D. One mechanic told me to use a reamer to clean out the carbon deposits, another told me it's not necessary. What would you do? Your votes determine how I'll do it. Thanks.

Alex

I was just debating the same
 

I was just debating the same, but when I pulled the bad plug out, it really didn't seem like it was all that carboned up.

I thought about using a 6mm allen, but the access was a bit of a PITA. Even with a reamer, access doesn't look that great for at least 2 of the 5 plugs.

alec

It may not be that carbon build up occurs ON the glow plug... it may exist IN FRONT of it.. thus does not come out with the plug... or show that it is needed by examining the plug....
Since this is one of those " Once in a quarter of a million miles" deals... and a special tool is made for it...I say,,, if the hassle of taking the plugs out is already expended... why not clean it out while you are there ?

leathermang:

I was wondering the same as I just did mine with no apparent improvement. Never dawned on me to ream it out until last night when looking through the performance catalog (I noticed the tool).
Are you familiar with how the carbon builds up in there? You eluded to the face that it might be blocking the tip of the glo plug.
I'm wondering if I should yank them out and re-do it?

Don

Don, I just figured that if pulling and cleaning the plugs would take care of carbon build up they would not have a tool to go in there and ream...It was just an "old mechanic" guess that led me to that place... I have no direct information about the carbon placement... but plan on pulling my precombustion chambers the first chance I get....
If what you did could normally be expected to make an improvement and did not, then I would think going back in and reaming would be logical....
If you do ream I suggest that you pull the injectors and vacuum from the top with the glowplug holes open before buttoning back up....

I ALWAYS use a glow plug reamer when I replace a set of plugs. You also need to crank the engine after you ream each glow plug hole to blow the loosened carbon out. There are two types of reamers, one type has the universal attached to it for #s 1-4 and there is another type used for the #5 hole which looks like a glow plug itself and threads into the hole.

Additionally, ALWAYS use some copper anti-seize paste on the threads of the glow plugs. Wurth CU1100 is very good.

The reason I suggested using a vacuum, even though I had seen the ' crank' instructions in the shop manual is I was afraid that it might suck some of the carbon down into the precombustion chamber holes.... depending on the starting place of the piston when the starter is activated...but probably if it did it would just be forced out when the piston reverses...

I have read several posts regarding this subject. I plan to replace the plugs on my 300sd soon and have this question, what does a reamer look like and where can I get one?

Any pics?

Thanks

Part number 617 589 00 53 00 available from any MB dealership.

Ok, well turns out my problem is much larger than the plugs. Maybe it's the relay, I don't know. Thanks for the votes. when I change them, and I will soon, I'll use a reamer.

Alex