Does anyone read the FSM ?
If the carbon builds up in front of the glowplugs... it happens gradually.... finally hitting, if the rest of the system is strong.... when you need it in the winter.. IF all your other system things are strong enough to not need it in warm weather.
Anyone consider what bad effects might come from using the wrong ' drill ' or a homemade reamer of the wrong size ? Is it worth the chance ? Is there one available in our loaner system ?
Also.. if the carbon builds up to where it touches the glow plug... that can short/burn it out.... so some ' preventative maintenance ' might be worth it . Every few Decades.. lol

If someone chooses a drill bit that is too large to fit in the hole and they are unable to figure that out, their life is probably filled with "bad effects." They should leave the hood in the closed position.

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.


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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.

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.

Don't waste your time going to a CNC machine shop. They will not have what you need. Buy the proper tool of make one. Picture a glow plug with the hot section replaced by a 7 mm drill bit. That's how I made mine, with a burned out glow plug and a 7 mm drill bit.

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.

I am NOT talking about a machine shop....

I am talking about a shop that sells tools to machine shops.

This is where one obtains the highest quality reaming tools and that is where I'm gonna get my reamer from and make the tools

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....

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

The thread size of the Glow Plugs for my 1984 300D are M12-1.25.

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?

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