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Old 05-04-2003, 08:04 PM
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Join Date: Feb 2003
Location: shelby, nc
Posts: 35
injector sealing washers

What is the purpose of the sealing washers?
I don't have them in my '80 240D -- I did not install them when I rebuilt the engine, and it runs perfect. Will any damage result?
The washers are installed in my '79 300CD I rebuilt, and I am having problems with "nailing" or "pre-ignition" noise.
What would it hurt to remove them from the CD and would it help the noise?


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Old 05-05-2003, 01:27 AM
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Join Date: Feb 2003
Location: TN
Posts: 302
I'm not sure what leaving the injector seal out will do to a Benz with a cast iron head over time, but with the VW Rabbit type engines (Aluminum head-Same type of injector ) I remember it being said that it would ruin the head over time.
As for nailing, TheBenzBin web site has a info page about is caused by use of the injector over time(about 100k) which weakens the spring in the injector thus injecting fuel too soon into the cylinder, and if bad enough, trying to drive the piston back the wrong direction. Very bad for the engine!!!
I've had an engine apart that I suspect had this broke the piston and multi-cracked the head in the cylinder that apparently had the bad injector.
I think anyone with this problem needs to remove their injectors and get them tested ASAP!
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Old 05-05-2003, 10:25 AM
Senior Member
Join Date: Jan 2003
Location: kansas
Posts: 100
that "sealing washer" is actually a heat shield, which prevents damage to the nozzle tip face from the extreme heat of combustion. all mbz diesel engines used these. damage to the nozzle tip face will be slow, but it will eorrode the nozzle tip face over time. i would advise getting a set installed in your 240, also, replace them everytime you remove a nozzle. they seal when "mashed" into the prechamber, so once "mashed" or "compressed" they will not seal properly again. be sure to clean the chamber and face of the nozzle before reassembly to promote good sealing.
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Old 05-05-2003, 11:55 AM
Join Date: Jul 2001
Location: Old Lyme, Connecticut
Posts: 3,596
If you look at how the injector fits into the prechamber, there is no heat transfer path for the injector nozzle body to the head. Thus, the washer with the pattern cut into it, which is to ensure the nozzle body surface at the bottom of the injector contacts the raised ring at the inside diameter and then is allowed to conduct heat away and out to the prechamber body.

I am not certain but I also think this part helps keep combustion junk out of the injector to prechamber threaded bore. Since the injector bottoms on these seals/heat shields and there are no other sealing rings or sealing devices it seems they must also perform that function as well.

Overall I think it is not wise to run without all the parts the engineers included in the engine design. I would put them back in and just figure I might have been lucky nothing bad happened that I have noticed, so far. Good Luck, Jim

1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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