2006 E320 CDI weeping/leaking fuel line(s) R&R?
 

Just as the 99 E300 fuel lines need for replacement, I'm getting the indicators of diesel fuel leaking under the hood in the CDI's engine compartment.

Longer cranking time to fire, & diesel fuel leaking on the floor of garage, accompanying the wet diesel fuel smell after any shutdown, necessitates delving into it now.

This is my first time doing the CDI's lines. Is there a tutorial / special tools on this procedure that one of you guys in the know can alert me to? Or, is it a straight forward, easy R & R?
Probable replacement parts/lines needed?

I haven't started the project yet, so I haven't located the leak(s) as of yet.

Any helpful advise appreciated!

Is there a Mercedes Service Manual available?

Fairly easy job. The most difficult part is the plate covering the access to supply and return lines at the HP pump. The plate has 3 torx bolts holding it, and the bottom one is a little difficult to access. Once you remove those three bolts, the plate is still "captured" by the serpentine belt among other things, but can be rotated down out of the way while you change the hoses.


5/16" SAE30R9. About 8ft will do the four hoses on top of the motor


...and remember not to start the engine without re-securing that front plate!!

Great advise and precautions!

Believe it or not - I need to buy the screw drive that will fit/unscrew the screws securing the decorative plastic extruded engine housing-cover to get to the fuel lines.

In the 3.5 years I've owned the car, I haven't done the maintenance/mechanicing on the car other than R&R of the engine mounts, cabin air filter, main battery (in trunk) & auxiliary battery under the hood (bonnet).

I need to procure the tool to fit the engine housing cowl - then, I may or may not possess the particular torx tool?

Once I get the cowl off, I'll probably be able to see where the fuel is dripping from.

My plan is to then take photos of the scene and go to the MB dealer in my other vehicle to buy a full set of replacement plastic lines and O-rings. I don't know if I will have the ability to change the hard plastic lines at their fittings - but will have to learn this procedure to gain the knowledge to become proficient, and to save the labor costs involved.

While I've got the cowl off, I can get a gander at the injectors, and see if the Black Death fuel oozing is present on my '06 CDI engine top. However, I believe that condition mainly afflicts 2005 injector design. I'll also be able to familiarize myself with the glow plugs locale and view the thread covered fuel return/equaling lines.

Re-read sparks post, the CDI's thankfully don't use the stupid plastic snap fitting fuel lines with the o-rings. Regular old 5/16th low pressure fuel hose is all you need for this job.

I will do it!

I think I'll be much more at home under the hood (regards fuel lines) of my I6 CDI, than the W210 E300. Sheesh!

The CDI engine bay is much, much cleaner than any of the OM engines with the inline injection pumps. Did a glowplugs change in an 06 CDI on Sunday and it took a grand total of about 20 minutes. Fuel filter changes are trivial and the electric fuel pump makes bleeding as easy as turning the ignition key to position 2.

It's a breeze to do basic maintenance on an OM648.

The only caution I can throw out (and this is probably true for any CAD-modeled engine)...

The LP fuel hoses on my OM606 and OM642 are specifically molded to fit around obstructions in the engine bay. Regular fuel hose will not be so molded and may be difficult to fit into place without kinking. On the 603 the hose runs are just gentle sweeps between components so everything works with just regular hose cut to length.

May have to pull the old hose and use it as a template. Form the new hose with a heat gun and a pan of ice water to heat, bend, and set it in place. If you don't have a heat gun but have a gas stove top, that would probably work too.

I know on the 642 they went to a fancy assembly of push on connectors at each injector for the return lines, not sure if that was used on the 648.

Regular SAE30R9 fuel hose is fine...no custom bending required. There is a bracket right up on top that keeps both HP pump hoses in their proper place. R9 is critical to resist harsh fuels and handle 65psi. Regular low pressure fuel line (R6 or R7) will burst. (It happened to me...400 miles from home...needed to do a MacGyver fix, but that's a different story)


The torx bit to remove the plastic engine covers is a male bit...Torx 30 if I recall correctly. The torx socket (female) is needed for the above bracket, and the front plate. That front plate removal needed a very short extension on my ratchet...about an inch.


When you have your engine covers off, check your injector return lines. I had one pop off and spill fuel, which makes it's way to the rear of the engine and drips down onto the bellhousing. That may be the source of your leak.

...and if you do find bad injector return lines, replace them with this:


E320 CDI return fuel line replacement with Teflon Tubing - Mercedes-Benz Forum


I bought everything exactly as described and it worked like a charm.

spark3542 - cannot thank you enough! Will report as I can.

For the e-torx socket get this set
https://www.amazon.com/gp/product/B0002NYBVO
Not the one from Hazard Frought. The HF set does not fit the splines correctly since it is a Chinese copy and can strip out the bolt. The Lisle set is US made and they paid the $$ to license the Torx design properly.

The Lisle sockets fit very snugly on the bolt. In fact you have to be careful because an E12 socket will "almost" sit down on an E10 bolt and if you are not careful that will strip it out. Found that out the hard way on my OM642 oil cooler job. Luckily it did not destroy the bolt and it was a one use only bolt that was getting replaced anyway.

Where can I source the 5/16" SAE30R9?

I'm at AutoZone, and their only fuel line is black, part # is 5/16", and it's Low something on it.

Clamps......? What do I need in the way of clamps?

I got my hose off a "popular" auction site.


The clamps you can reuse. A tiny flat blade screwdriver releases them, and pliers clip them back together.

How timely!

That was my 1st question here.
How the heck do you deal with the factory clamps?
Are they really good going forward, or, do they lose their ability at some point in staying solidly clamped down?
They're new territory to me.


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