im am going to change my valve cover gasket on my 240D im wondering if there are any precautions I need to know about. Also is it okay to re use the same fuel lines the go to the fuel pump?

If you have a copy of the factory service manual, I would read that for the procedures (the maintenance manual has the valve adjustment procedure which covers removing / installing the valve cover).

Removing the flexible fuel lines: be careful that you don't score the injector nipples, which may cause leaks.

I would not recommend re-using the flexible fuel return lines - they get brittle with age and can fail. However, they usually fail gracefully (if you have the cloth-covered OE type) so you can risk it and may only end up with a small fuel leak. I'd cut off about 3/4 of an inch from each end to expose some "fresh" line to push onto the injector nipples.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Not sure on the 616 (your 240D has a OM616, 2.4 liter) but on the 617 (5 cylinder, 3 liter version of the same engine) the cover needs to be flat or it won't seal. I did a thread on flattening mine on a table saw top but you can use anything that's dead flat including a piece of 1/4" thick glass (1/8" will be too prone to breakage). Basically you stick a couple of pieces of 80 grit straight line sander paper (available from any big box auto parts store) down on your flat base and work the cover until it's flat. The paper has a sticky back so it's easy to stick it in place. As you start working on it you'll see the spots that the paper doesn't touch - keep going until those go away. Worked great on mine.

BTW - not that it matters but that's a cam cover - it covers the cam as well as the valves.

Dan

Try to avoid using the Victor Reinz part (very common and usually the least expensive online). In the last few years there have been threads about people having issues with these being hard to install (hard to keep in place when putting back the valve cover).

If you have already purchased a Reinz, I suggest you leave it in the freezer the night before to shrink it up a bit.

If you mean can you re-use the fuel return lines (soft lines), the answer is no, you buy new and cut it to fit. I prefer to buy it by the yard (some vendors sell it "precut" and this I find stupid as it wastes line).

If you mean the hard steel lines to the pump, of course those are re-used, they should last the life of the car. Just be careful not to bend them.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Might a thin film of Permatex #2 (non-hardening sealant) hold the gasket in position while bolting down the cover? I use the stuff all the time, and it scrapes off pretty easily next time you're in there.

Nice tutorial: Mercedes Diesel Valve Adjustment Procedure

And what do you do if it easily scrapes off into the head of the engine?

Dkr.

Just to clarify, if you want to use some form of make-a-gasket, just dab a little onto the channel of the valve cover gasket in a few places, then press it onto the VC and hold in place while it sets up. This helps to keep the gasket in place, however the last time I did the job (with a VR gasket) I found the freezing was sufficient to get it to grip properly.

You should not use any form of gasket maker to seal the VC gasket to the head. If the job is done properly, none should be required.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

^ Exactly right, just enough to add a bit of stickiness to help hold the seal in position.

Don't like to use any form of gasket sealer. To keep gaskets in place during assembly, I use a film of grease.

I've never had to pull fuel lines to change a valve cover gasket. Ditto on skipping Victor Reinz.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

I'll have to buy a piece of glass and see how flat my covers are. They leak after gluing and are Victor Reinz. Someone reported the VR after ordering from Mercedes.

OP, you do not have to pull the return lines. You may tie them to the hard lines which may be easier but should not be necessary. Practice positioning the cover & setting it in place a few times before you try it with the gasket. You'll be glad you did.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.