OM603 injector torque discrepancy - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 04-27-2011, 03:57 PM

I'm in the process of installing a new-to-me #20 head (ex-Sixto) on my 1987 300D Turbo (W124, OM603). The head had been on Sixto's 350SD until the car was totaled in an accident. The head uses injectors that sit at a 5º angle and are screwed into splined prechamber lock rings.

The FSM "Service Manual, Diesel Engines 603, 603" says in section 07.1-230 "Removal and installation of injectors" that the injectors are to be torqued to 70-80 NM (about 55 ft-lbs) with "special tool" 001 589 65 09 00, which is just a fancy socket. [A 1-1/4 inch deep socket substitutes just fine.]

The problem is that FSM continues on the same page to say "with inclined injection 30 NM." That is a major difference from 70-80 NM! My Haynes manual says 75 NM. My indy mech checked his sources and they say 75 NM. I have searched this forum and have found several references, all of which say 75 NM.

Is this an error in the manual? I don't want to make a mistake.

Jeremy

winmutt · #2 04-27-2011, 05:48 PM

I'd go with 30NM then do the soapy water test for leaks.

Diesel911 · #3 04-27-2011, 08:08 PM

Quote:

Originally Posted by Jeremy5848

I'm in the process of installing a new-to-me #20 head (ex-Sixto) on my 1987 300D Turbo (W124, OM603). The head had been on Sixto's 350SD until the car was totaled in an accident. The head uses injectors that sit at a 5º angle and are screwed into splined prechamber lock rings.

The FSM "Service Manual, Diesel Engines 603, 603" says in section 07.1-230 "Removal and installation of injectors" that the injectors are to be torqued to 70-80 NM (about 55 ft-lbs) with "special tool" 001 589 65 09 00, which is just a fancy socket. [A 1-1/4 inch deep socket substitutes just fine.]

The problem is that FSM continues on the same page to say "with inclined injection 30 NM." That is a major difference from 70-80 NM! My Haynes manual says 75 NM. My indy mech checked his sources and they say 75 NM. I have searched this forum and have found several references, all of which say 75 NM.

Is this an error in the manual? I don't want to make a mistake.

Jeremy

I thought the Injectors screwed into the Prechambers on the ones with Splined Prechamber Retainer Rings?

Jeremy5848 · #4 04-27-2011, 11:39 PM

Quote:

Originally Posted by Diesel911

I thought the Injectors screwed into the Prechambers on the ones with Splined Prechamber Retainer Rings?

Correct. That's why the torque spec is only 30 NM -- the prechambers are aluminum. The older heads with vertical injectors screw into the (steel) retainer rings and can handle greater torque.

Turns out the FSM has an error in page numbering -- the NA engines and the turbo engines have separate "Diesel Fuel Injection" sections but they numbered the pages the same. The NA version mentions the lower torque for inclined injectors while the turbo section does not.

Jeremy

Diesel911 · #5 04-28-2011, 01:22 AM

Quote:

Originally Posted by Jeremy5848

Correct. That's why the torque spec is only 30 NM -- the prechambers are aluminum. The older heads with vertical injectors screw into the (steel) retainer rings and can handle greater torque.

Turns out the FSM has an error in page numbering -- the NA engines and the turbo engines have separate "Diesel Fuel Injection" sections but they numbered the pages the same. The NA version mentions the lower torque for inclined injectors while the turbo section does not.

Jeremy

I do not believe the Prechambers Are made of Aluminum.
However, the are made of a heat resistant Metal that may well be softer than Steel.

I was with one of our Members when we pulled the Prechambers out of Head (an Aluminum Head) but this one had the slotted Retaining Collars. But, the Prechambers were not Aluminum.

This is not for the same model Engine but the newer models are subject to the same heat so I believe would use a similar material.
From another members Thread:
Prechamber Material, Precombustion Chamber Material
Mercedes uses Nimonic 80A for the prechamber.
That information and figure come from an SAE paper published by Mercedes titled "The Turbocharged Five-Cylinder Diesel Engine for the Mercedes-Benz 300SD". It's an excellent read, and I highly recommend it!
http://www.peachparts.com/shopforum/showthread.php?t=232935&page=9

vstech · #6 04-28-2011, 08:49 AM

Quote:

Originally Posted by Diesel911

I do not believe the Prechambers Are made of Aluminum.
However, the are made of a heat resistant Metal that may well be softer than Steel.

I was with one of our Members when we pulled the Prechambers out of Head (an Aluminum Head) but this one had the slotted Retaining Collars. But, the Prechambers were not Aluminum.

This is not for the same model Engine but the newer models are subject to the same heat so I believe would use a similar material.
From another members Thread:
Prechamber Material, Precombustion Chamber Material
Mercedes uses Nimonic 80A for the prechamber.
That information and figure come from an SAE paper published by Mercedes titled "The Turbocharged Five-Cylinder Diesel Engine for the Mercedes-Benz 300SD". It's an excellent read, and I highly recommend it!
http://www.peachparts.com/shopforum/showthread.php?t=232935&page=9

no, the prechamber itself is not aluminum, but the collar nut that retains it is.
and that's what the angled injectors thread into. so far, I've not had the luck to obtain a 22... but I'm looking forward to it...

Jeremy5848 · #7 04-28-2011, 12:37 PM

Quote:

Originally Posted by vstech

no, the prechamber itself is not aluminum, but the collar nut that retains it is.
and that's what the angled injectors thread into. so far, I've not had the luck to obtain a 22... but I'm looking forward to it...

The angled injectors definitely screw into the top of the prechambers . . . I installed mine yesterday. The vertical injectors screw into the retaining ring, which is steel.

Thinking about it, I agree that the prechambers cannot be aluminum -- it would melt at those temps. Some kind of light-weight non-ferrous metal, then. Also, the angled injectors do not screw in the full length of their threads because the threaded opening at the top of the prechamber is only 5 mm deep. That is probably why Mercedes lowered the torque spec.

Jeremy