I'm getting ready to replace the chain guides on my 1988 420SEL since it has 117K miles. While I'm in there, I plan to check the condition of the chain, but right now I just have the parts to do the chain guides and cam oilers. I have a question about the fuel lines... there are two fuel lines attached to the left side cam cover, and I can't get the cover off without removing the fuel lines. The rubber lines appear to be permanently fixed to the ends, which have flares. My question is, to remove the fuel lines, should I disconnect them at the flares? At the engine end?

I don't know about the fuel lines, but you might as well replace the chain.

Sixto
95 S420
87 300SDL

To answer your question, yes. Also as Sixto said i would replase the chain and the chain tensioner.

I have a 1989 420SEL and I can get the left valve cover off without removing the fuel lines. The removal is tricky but achievable. I just had it off yesterday.

It is difficult to explain how to do it. Basically, after removing the 4 screws, try to rotate the cover when it is snug up against the fuel lines. Keep rotating until it is against the firewall foam, at the rear end. Then move it foward. Once it is clear of the last cam tower, it is easy going.

If you want to disconnect the fuel lines, do so at the fuel distributor. Be prepared for lots of fuel. I watched a pro do it once and he used a home fabricated hose, to connect the fuel line to the fuel return line, because the fuel just keeps coming. I guess you could use a couple fuel line clamps, one on the rubber part of each line to eliminate the flow. It will be hard to start, if you let the fuel flow out.

Also, you may choose to have spare valve cover gaskets available in case the old ones are hard or leaky.

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1989 420 SEL

If the air tubes to the injectors have never been changed, they may be hard and brittle. Also, if they are old, they may be very difficult to remove without ripping. So you may choose to replace them.

When replacing the valve covers, I find it easier to remove the air tube, then replace the valve cover, and finally replace the air tube. A little silicone lube on the air tube junctions makes for easier removal next time.

One more thought. If you are going to use the old valve cover gasket, be sure to remove all oil from the gasket, including the groove and all oil from the valve cover. By doing this, there will be less probability that the gasket will fall off, when the cover is replaced onto the head, one of those tender moments when you may want to swear if it does fall off.

Those valve cover bolts, 3 NM only!

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1989 420 SEL

Before i removed the fuel lines, i tied a string on each one. After it was off i tied it to the hood lock and lost very little fuel.