Glow Plug Reaming - PeachParts Mercedes-Benz Forum

Benzova · #1 05-01-2013, 11:49 AM

Hello, I am getting ready to replace the glow plugs on my 1980 300sd.

I would like to ream the chambers before I install the new plugs but I have a few questions about the process:
1. If I ream the chambers, won't this possibly dislodge carbon deposits and send them into the cylinder where they can damage the block or jam a valve?
2. If I use grease on the reamer in an attempt to catch the carbon deposits, what kind of grease should be used so I don't affect the function of the plugs?

Thanks.

Jadavis · #2 05-01-2013, 12:25 PM

Welcome to the forum!

The search function is your friend on here. You are not the first with these questions.

There is a guy on here that makes and sells the reamer tools. Diesel911, I think.

There is some discussion about reamers here:
Glow plug replacement

Diesel911 posted there. You could PM him to see if he is still selling the tools.

Jim

Jadavis · #3 05-01-2013, 12:33 PM

Holy crap! The moderators put up a link thread for glow plugs. It should be a gold mine for you.

Glow plugs link thread

Jim

Diesel911 · #4 05-01-2013, 12:35 PM

Quote:

Originally Posted by Benzova

Hello, I am getting ready to replace the glow plugs on my 1980 300sd.

I would like to ream the chambers before I install the new plugs but I have a few questions about the process:
1. If I ream the chambers, won't this possibly dislodge carbon deposits and send them into the cylinder where they can damage the block or jam a valve?
2. If I use grease on the reamer in an attempt to catch the carbon deposits, what kind of grease should be used so I don't affect the function of the plugs?

Thanks.

I don't have no more Glow Plug Reamers for Sale and no plans to make any; try eBay or your favorite internet seller.
After the Glow Plugs are removed you get the Glow Plug Reamer and fill the Grooves/Flutes with Grease (Vasoline is too runny for that). The Grease traps the major pieces of Carbon.
You may or may not need to wipe out the Carbon and regrease the Reamer between reamings. It depends on how much Carbon comes out.

After that you tie down the Manual Shutoff Lever or have someone the Manual Shutoff Lever Down (and close their Eyes) and the Engine is cranked and that blows out any loose Carbon out of the Glow Plug Holes.

The above is in the Factory Service Manual.

Benzova · #5 05-01-2013, 08:32 PM

Yep, I found some info about the grease and thanks for the info about cranking the engine to blow out the deposits.

here's a pic of the grease used:

@ #20:

My weird to me glow plug situation . . .

leathermang · #6 08-09-2015, 02:07 PM

Quote:

Originally Posted by Diesel911

......After that you tie down the Manual Shutoff Lever or have someone the Manual Shutoff Lever Down (and close their Eyes) and the Engine is cranked and that blows out any loose Carbon out of the Glow Plug Holes.

The above is in the Factory Service Manual.

I doubt that last part about cranking the engine is in the FSM... since it is only 50percent correct... every other stroke will be pulling any loose carbon into the bottom of the precombustion chamber... and blocking those tiny 7 radial holes which the atomized fuel is supposed to come out of into the combustion chamber...
Done correctly there really should not be any loose carbon... having been brought back out on the stiff grease in the flutes of the reamer...

m1tch · #7 08-09-2015, 02:50 PM

Check out the reamers from Mercedes source.

charmalu · #8 08-09-2015, 11:38 PM

You can make your own reamer from an old Glow Plug

This link if from the above link posted. Post #20
My weird to me glow plug situation . . .

Charlie

sent from my pos computer

mannys9130 · #9 08-10-2015, 03:05 AM

Holy dead thread revival Batman. 2 years old. I hope the OP has reamed the holes by now.

leathermang · #10 08-10-2015, 07:26 AM

These threads are not just for the OP.... When I went looking for a reference to a current question I found something needing correction in this one... so I did...

toomany MBZ · #11 08-10-2015, 06:53 PM

I use a KB unit and use moly-be-damned grease.

When I feel up to it, I also use a vacuum on the holes after.

ambush276 · #12 08-10-2015, 07:15 PM

edited

leathermang · #13 08-10-2015, 07:22 PM

Saved in case I need it...

Diesel911 · #14 08-10-2015, 10:59 PM

Quote:

Originally Posted by leathermang

I doubt that last part about cranking the engine is in the FSM... since it is only 50percent correct... every other stroke will be pulling any loose carbon into the bottom of the precombustion chamber... and blocking those tiny 7 radial holes which the atomized fuel is supposed to come out of into the combustion chamber...
Done correctly there really should not be any loose carbon... having been brought back out on the stiff grease in the flutes of the reamer...

Sorry I did not answer this sooner. Good thing the Thread came back to haunt us.
The truth is the instructions on how to get loose carbon out of the Precombustion Chamgers is in the Mercedes 240D manual. See pic.

I don't know why the same instructions are not in the 300D CD Service Manual set. But, it may be in the printed manual.

How it works. When the Piston is going down on the intake Stroke the intake Valve is open. That means the open intake valve is the way of the least resistance.
Also at the Tip of the Prechamber is something line 5 smaller then 1/16 inch holes so there is not a lot of air flow possible through them.

Also the Piston creates a negative pressure as it goes down but it is the about 14.7 psi of atmospheric pressure that pushes into the cylinder. Apparently 14.7 pounds of pressure and the flow produced by that is enough to pull anthing but the tinest stuff, if at all down into the Cylinder.

However, when the Piston comes up on the compression stroe squeezine the air throug those precahmber holes creates all kinds of turbulance to blow loos stuff out.

Whan the Piston is coming down on the Power Stroke I am not sure why stuff does not get pulled in. Perhaps the Injetor squirting wets down the Carbon and prevents that from happening.
It is in section 15-515 in the 240D manual

leathermang · #15 08-10-2015, 11:13 PM

Here is the problem with trying to blow it out with piston movement....
The glow plug hole is 90 degrees to the precombustion chamber and the only access to the precombustion chamber is via approximately 7 radially drilled holes at the bottom.... meaning in a plane parallel to the top of the piston.....because that is where the fuel spray needs to be put when the engine is running...
You can not get enough air flow power to count on blowing out loose pieces of carbon...
So, too many 90 degree turns....and too small an access to the air connected to the glow plug hole...
There might be a reason it was not in later FSM's.....
Either use heavy grease to capture the carbon or take out the injectors and blow out from that side...