I am positive I have the right tool. It's exactly the same threads as the glow plugs which I pulled from the car though the thread area is a little longer. The diameter of the tip of the reamer is slightly larger than the plug tip.

It will not penetrate the hole far enough to get to the threads though the plugs fit there fine. I tried tapping the end of the reamer to get some of the crust off so as to get a 'bite,' on the carbon to no avail.

Is there a recommended solution to put in the holes to soften the carbon up a little or am I just being a twat for not hitting the reamer hard enough?

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84 300SD
85 380SE
83 528e
95 318ic

Never used the official reamer. I just ran a regular metric tap thru the holes. Not much carbon came off on the tap, and when I have had the injectors out in both 300D's, I didn't see any carbon down in the pre-chamber, so not sure the fuss is warranted.

I don't know what could be blocking it since the glow plug was in there prior. Granted the tip of the reamer is slightly wider, but carbon should be soft, unless yours converted to diamond. To be safe, go to the hardware store and find a metric nut that the glow plug screws into, then verify your reamer does too. You don't want to be messing up your head. It is a standard metric thread. You don't even have to buy a nut, my nearby Ace has a set of test bolts and nuts hanging on the nuts & bolts aisles.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

I will check the threads again though I'm sure they are the same. I've changed the GPs in this car twice in the last seven or eight years and I'm positive the head hasn't been altered for I ordered standard sized Bosch plugs for it. The reamer is a Hazet has numbers on the head which match the identical tool sold by several websites. I was sent the reamer for the 603 and had to return it for the correct tool and posted the numbers of the second reamer I received here to ensure I wasn't about to make a mess of this job/car.

I tried a small tap which was just slightly larger than the tip of the GP and I'm guessing you're right about the hard as diamonds. It felt quite like metal though I did get a sample of carbon dust on the tap.

I know MM oil is going to be slow go but I fear using anything but that and perhaps seafoam in the holes knowing that some will end up in the cylinders. I have the injectors out if that makes any difference.

Suggestions and discussions are needed here folks.

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84 300SD
85 380SE
83 528e
95 318ic

Quit telling people to use a plain tap. That's nothing like a glow plug reamer, so declaring the reaming of the plug chamber as "useless" is starting with an incorrect premise in the first place. You're only cleaning the threads using your method, not the glow plug chamber itself.

As far as the job in question, it's totally within reason to see carbon built up so thick that it's hard to get the reamer in (all the more reason to do it). I wouldn't suggest pounding it in as that will only knock stuff into the prechamber. Just start with your reamer coated in grease as usual and spin it as you try to push it in. Eventually it will cut through the carbon to the point where it will start to thread. This happened the first time I did my car. And yes, carbon can be hard. It'll sort of "squeak" and feel crunchy as you cut into it, unlike metal.

-Rog

Yes to previous post, except how are you sure you haver the correct reamer. If you cannot post a photograph maybe take some measurements O.D. of the reamer, length after the threads, or where you acquired it from.

Here's the order confirmation for the reamer I bought. I also posted a photo of the reamer here and a couple of guys confirmed it to be the correct tool for a 617 engine.

I shot a video of the hole and am in the process of uploading it to youtube. I'll post a link in asap.

I'm wondering if anyone ever cleaned these holes with a GP reamer before. It has over 300K on it.

Attached Thumbnails

 

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84 300SD
85 380SE
83 528e
95 318ic

For a short while at the very first the camera is in the injector hole so you're looking at the chamber. When the camera moves around so you can't really see what's happening I was moving it to the GP hole.

https://www.youtube.com/watch?v=hFXlJugqYC4&feature=youtu.be

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84 300SD
85 380SE
83 528e
95 318ic

video is private. change the settings.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

My bad. It was my first video on youtube.

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84 300SD
85 380SE
83 528e
95 318ic

I cleared four of the five holes the last one is a bugger but I've made a little progress on it. I've put MMO in the holes using a nylon or plastic pipe brush. It wasn't much bigger than the GP tip. I let it sit for about two hours.

Each hole has been the same problem. The reamer tip would stop at about the same location in each. The initial point of obstruction seems to be about the location of the smaller end of the taper where the GP seals combustion.

After two holes I considered the location causing the trouble and speculated if carbon hadn't gotten on the taper surface and sealed the cavity. Perhaps the anti-seize or ceramic paste was buildup and somehow contributed to the issue though I doubt either would serve as a mastic for carbon. ???

When that area was cleared by the tip of the GP reamer the process was easy. There was no 'working,' the tool back and forth nor was there enough resistance to cause any significant force. I'd guess it would not register on an old fashioned bar type torque wrench.

I only backed the reamer out of the hole once and that was just after it broke through the small cylinder were only the tip can go.

I think the MMO really made the job easier (disclaimer) though any petroleum based product which doesn't immediately evaporate may likely have done the same.

Has anyone had a similar problem with a 617?

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84 300SD
85 380SE
83 528e
95 318ic

Good video! It clearly shows a carbon-ed up glow plug seat on the head when you should see metal there.

After your're done reaming. take a large flat bladed screwdriver and wrap it with multi layers of thick Denim (old jeans, use duct tape so it stays), soak it with WD-40 (decent solvent for carbon), twist it back and forth to rub/ dissolve the carbon off the seat. Change Denim often till no more carbon is picked up by the Denim, till you see shiny metal. This insures a good seal on the new glow plugs and you won't have this problem again.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I sure will. I should have asked about that but I got so wrapped up in describing my plight and it's solution.

Do you have a theory as to how that surface became covered with carbon? The rest of the hole was pretty easy. It must have been reamed previously or it would have been a bear just like the taper.

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84 300SD
85 380SE
83 528e
95 318ic

ok... first, lets blow out the holes...

with ALL GLOW PLUGS OUT OF THE HOLES, crank the motor over a few dozen times... it'll blow out all the crap loose in the holes.

get a can of PB blaster, or AEROKROIL, or WD40... in that order... keep in mind... the PB is super stinky! but it cuts well.

soak the holes, let it sit, soak them some more, then spin the motor over.

when the mist stops blowing chunks, spray some more, and do it again.

DIRTY!! yeah... get em reamed, and keep em clean!

I'm not TOO far away if you need a hand.

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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 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Theories that come to mind:

Debris on seat (like what you have now)

Defective seat

insufficient torque. Use a torque wrench on the ones you can so you can get a feel for the ones you can't.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

All of the above, after completing the reaming I have a small bristle brush with my reamer kit to poke in and out, pulling out loose carbon. keep in mind if you think that those GPs haven't been reamed before, the valves should be due for an adjustment also.