Just noticed a few drips in the driveway when I left for the airport on this current trip. I popped the hood and took a quick look see around the injection pump, and everything is bone dry, so whatever it is, is coming from before the injection pump.

I'm not anywhere near my tools, so, once I get back, any thoughts?

Could be oil from the low oil sensor, they often leak.

__________________
1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250

It's definitely fuel, not oil.

First remove the decorative cover and inspect your fuel return lines or injector pressure lines for leaks. If that's good proceed on to check the fuel delivery side.

W210 fuel flow comes up into the engine bay via 2 steel lines from the tank (supply and return). These lines join to standard rubber hoses over to their first connection on the engine. These joints are made with Oetiker ("Click-R") hose clamps.

After that everything uses a quick connect fitting. Each of these fittings has an internal o-ring that are notoriously bad about leaking. ULSD seems to make this worse.

Also the jumper hoses are made of translucent plastic that becomes hard and brittle over time.

There is also an o-ring between the shutoff valve (black box on the side of the IP) and the IP body. This one leaks as well.

It is possible to inspect much of the fuel system without removing the intake manifold by draining and removing the windshield washer bottle. Note, don't remove the coolant lines in the lid, the entire heater assembly can be pulled out intact.

I suspect you have a leaking jumper hose or o-ring. The entire set of new hoses, with fresh o-rings, can be had for about $100. Be sure to study the EPC and don't forget the seals for the one banjo fitting on the IP return line.

One thing to note about the quick connector locks, they are like a little horseshoe. The "lock" position is where the clip is in the center of its travel. The "release" position is where the clip is fully pushed to the end of travel.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I had exactly the same thing, and it turned out to be leaky delivery valve seals. With the engine running, you could not see any leakage, but if I ran my fingers along the top and side of the injection pump, you could feel the dampness. The fuel would then work its way down into the belly pan, and finally leave a silver dollar size spot under the front of the car. Did the delivery valve seals, and that ended the leakage. Good luck

__________________
96 E300d

Good advice here, if you remove the WW bottle you will have a clear view of the IP.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

is bottom of IP dry? I had fuel leaking from back of shut-off valve. You can see video of this repair on my youtube channel, dieselmercedes. Good Luck !

My IP (in its entirety) was replaced about 10k ago before I bought the car (someone likely got screwed by the dealer), so I'm assuming it's one of the hoses that come up from the hard line in the engine bay. All the clear jumper lines look very new and are dry, so I don't think this is a delivery valve or jumper issue, but one of the main delivery lines.

I'm on the road through the weekend, but will poke around and take some looks at this next week.

Whatever I replace, I want to be biodiesel proof, so does anyone have any suggestions on where to obtain viton hoses/ o-rings for this thing?

Check McMaster-Carr. I haven't done so, but others say they have it. I buy many special industrial parts from them, both for home and in my day job. They are often cheaper than Home Depot and when not, their items are usually better quality.

I'll have to do start doing some digging. Does anyone happen to know the ID of the main fuel lines down there off the top of their head?

I recently bought Viton o-rings from Amazon (believe it or not). You'll end up with a lot of spares, but they're cheap anyways.

Check this thread for sizes:
http://www.peachparts.com/shopforum/diesel-discussion/177588-om606-962-o-ring-size.html

__________________
Current rolling stock:
2001 E55 183,000+ Newest member of the fleet.
2002 E320 83,000 - The "cream-puff"!
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+

Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
1993 500E - sorely missed.
1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years.

Ordered the Viton o-ring kit from fryerpower, all the clear tubes, and am picking up some Viton hose from a local shop, so hopefully with all of this in hand, and everything gone through, this won't be an issue again anytime soon.

Don't forget the o-ring on the fitting where the return line plugs into the filter assembly. I did, and had fuel leaking from there and blowing all over the IP.

__________________
'97 E 300 D

Well, turns out I am leaking at the shut-off valve to injection pump.

Given that my IP is less than 10k old, and it sure looks like the SOV and all those jumper lines are the same age, should I replace the SOV while I've got it out? I hate taking things apart and re-using old parts... but there's also no point in replacing perfectly good parts....

If you are leaking behind the SOV it's a simple o-ring that takes a half hour to change. Most of that time is sucking the washer fluid out so you can get to the valve. Unless the SOV itself is damaged.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech