X2, I replaced the O-ring on mine and that stopped the leak. I think it took 5 minutes, possibly 10 if the spring goes flying.

__________________
1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

Nevertheless I replaced mine with a used one. It was a real PITA trying to remove the upper mounting bolt and a couple of hose clamps. I guess this one hadn't been touched since the original installation.
Do you guys typically remove the unit when replacing the o-ring?

__________________
1995 E420 152k
1991 300D 2.5 348116 daily driver
1992 300E 2.6 196k-work in progress(head gasket)
2002 BMW 745Li 93k

NO

__________________
1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

I do not believe any coolant is used to heat the fuel.

The thermostat simply reroutes the fuel up to the head where it is preheated.

__________________
1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

http://www.fuelly.com/sig-us/40601.png

Mine has a coolant to fuel heat exchanger.

Why route fuel "into" the head?

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

The 606 heater is in the head. No coolant lines go to it. 603 and 602 is coolant heat.

__________________
What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

Good info thanks. But your presumptions about the WT is wrong. I think the idea is the customer won't have the problem again. In the south, i would say that is a good way to go. Bypassing is a permanent fix. Replacing an O-ring is not. Can always hook back up. Simple is good.

And whose to say a professional did this? Could've been done by a desperate person leaking fuel like the OP with a mercedes screwdriver and no o-ring handy. I bet the OP wishes he had known to bypass the thing.

__________________
What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

My 602 doesn't use coolant.

I just replaced all the hoses at the thermostat, all were fuel lines.

__________________
1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

http://www.fuelly.com/sig-us/40601.png

I suppose the reasoning was that the head heats up faster than the coolant.

__________________
1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

http://www.fuelly.com/sig-us/40601.png

OW,

Quote:

"My 602 doesn't use coolant. I just replaced all the hoses at the thermostat, all were fuel lines. "

[Then you've nothing to worry about...Your "Head" will warp within ten minutes...
And then you can move on to other pursuits.]

The other end of those Thermostat fuel lines (That dis-appear under the Intake)
Connect to the Coolant/Fuel Heat Exchanger,which is plumbed into the Coolant
System.

Part # 233 is the Heat Exchanger.
Part # 245 is the o-ring.
Part # is the securing clamp.

Attached Thumbnails

 

__________________
'84 300SD sold
124.128

Page 6, Section E describes how the fuel heat exchanger functions. Fuel travels up the tubes to the heat exchanger, where coolant in the head is exposed to the heat exchanger (the actual design of the heat exchanger is not discussed, so I am not clear if the fuel is routed through a U-tube into the head a short distance, or what...).

071.-0010 Function of injection system

__________________
1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

http://www.fuelly.com/sig-us/40601.png

The fuel heater lines are melded with a heater line. You'll see heater hose going to the same spot as the fuel lines. It doesn't actually go into the head though.

Mine was leaking badly lately. The O-ring was a little over a dollar at the local M-B dealer, and it only took about 20 minutes to remove and replace it, you do need a set of split ring pliers to get the metal circlip off- I bought some at harbor freight for $3.

Its a good idea to replace the hoses while you are doing it and not have to mess with them again for a long time.

__________________
1991 300D 2.5 turbo
1991 560 SEL
1987 911
Toyota landcruiser
Atlanta, Gawga