I took all mine out this past fall, found barely any carbon on any of them and they all came out very easily - got a 7mm (I think) drill bit and didn’t get damn near anything out of the holes. A wire brush that would expand larger than 7mm once fully inserted and some carb cleaner, and I imagine you’d get a lot of carbon moved around and some of it out. I’ve just had not so great experience with moving it around vs. extraction, where by just moving it around a bit it tends to cake and build up and cause problems that weren’t there in the first place. So count me among the group that didn’t ream.


Sent from my iPhone using Tapatalk

I know the forum has instructions on making your own creamer with a glow plug body and a drill bit.
I seem to recall it was a 7mm bit.

A search here should turn up the specs, but I'm on my phone and can't search.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

If one does their own glow plug maintenance, it does not make sense to not ream. WITH THE RIGHT REAMER. Coat it with assembly grease to trap the carbon chunks.

You can buy the Hazet tool for $60. or you can buy Kent's fabricated tool for $34.50 and it comes with a brush, an instruction sheet and a handful of LemonHeads.

A hardware store reamer or drill bit can work but the above options have a threaded portion to ensure the reamer goes in straight so as to not damage glow plug hole threads. It also limits depth so you do not damage the prechamber by going too deep.

^ This. The correct tool pays for itself the first time you use it. The "coat with grease" step is an important one, and is prescribed by the FSM, do not skip it. I cringe when I hear of folks dry reaming, or jamming random long tools in there. If you're not going to do it correctly, why bother with DIY, just pay the dealer to do it.

__________________
1998 E300 turbodiesel

America's Rights and Freedoms Are Not The Enemy!

I just feel like I'm comfortable using my own reamer. That I can buy locally for $10.

I just need the specs... How big is the diameter of the reamer... 7mm???

How deep is the hole?

That's the info I need now. Renting a tool here and paying shipping both ways will be almost $20 bucks when I can just buy one myself and make it at home for $10 and use it for a life time.

__________________

Lots of good comments here .

I saw some inexpen$ive glow plug reamer kits on Amazon but no one has yet mentioned the correct thread size and pitch....

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Just use an old glow plug as a guide... go no deeper that the element, and mount the reamed bit in the plug body... 7mm

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

If you're going through the trouble to ream your glow plug holes, just change the plugs while you're at it. Use Bosch or Beru and call it a day. If you're reaming the holes just to ream them then putting the plugs back in, that seems like extra work that's not necessary. What is the problem you're trying to cure?

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Interesting to read through this type of thread and see which people have done it properly before and understand that the carbon build-up is like concrete and which have never done it properly and think it's like cigarette ash that can be easily brushed or blown away...

Do it once the right way and then you'll understand. No you don't have to use an official reamer, but what you do use will have to accomplish the same thing.

-Rog

Thanks for the info guys. I think I got everything I need.

And yes I am changing my glow plugs to new plugs, that's the whole reason why I'm on the subject now

__________________

I made my own by taking a 7mm drill bit and drilling out an old glow plug. then set the length at just past a new glow plug and welded the threads to the drill bit. Now I just thread in till it bottoms out the threads. I ream out any time I pull a glow plug, as it only takes a few seconds and they come out much easier and cold starts are much better after reaming.

__________________
Von
Fairport, NY
1973 Unimog 416 Doka
1980 Unimog 416 Doka
1981 Unimog 416 Doka
1984 Euro 280CE w/diesel conversion
1985 300TD Estate wagon
(I really need to stop buying these things!)
http://vonsmog.com

If you're gonna make one, a drill bit is the better way to go.

1. You drill the hole in the glow plug with the same bit

2. It has more chip clearance than a reamer. I.e. it can hold more carbon.

3. A drill bit cuts into the carbon better than a reamer.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I'm happy I'm so rich I can afford Kent's reamer. One of the luxuries in life a millionaire can apparently afford which is evidently out of reach of the little guy

- Peter.

__________________
2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

"The" reamer, no, but something that accomplishes that purpose, very much so.

__________________
'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

So we have come to the conclusion that a 7mm drill bit is better than a reamer??

__________________