I have two questions? 1) How do I change the spark plugs on a 1998 S420 MB? 2) Where can I get a technician manual? I like doing the work myself to save money.

Thank You for Your Valuable Time
smitoryous

Hi. Very easy job. Simply remove the black plastic covers located in the center of the valve covers, remove the individual spark plug coils (8 of them), and change the plugs. Be sure to use some anti-seize on the new plug threads... just a dab, you don't need much.
You'll find many posts here about w140 service manuals. MB will now apparently sell you a CD with basic procedures at the dealers. You can also subscribe to ALLDATA on-line manuals which has more detail. For the most detail, you can buy on-line time with the MB site.
The attached pix shows the plastic covers removed and the plugs coils exposed. This should help you along.
I see this is your first post... you'll learn much about your W140 if you hang around here a bit. Don't hesitate to ask questions... the folks here are terrific and will help you.
Welcome to the best Forum on the web.

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KenP

1996 S500 W140 Coupe

Thank You for your help.

Now that thats done. How do you replace the injectors? I pulled the fuel line off and put it back and gas comes out and and won't seal. Are there gaskets or seals that need to be replaced? I believe that they are injectors. Where the fuel line looks like a U shaped around the top part of the engine. I should have never pulled them off. I just need help.

Thanks

Hi. If you look at the pix I posted earlier, you can see a couple of the fuel injectors just above the valve cover.
The injectors are held between the fuel rail (that "U" shaped tube) and the intake manifold.
The top and bottom each injector has an "O"-ring to seal it and prevent leaks.
You'll have to replace the seals and make sure the mating recesses for the injectors are clean.
Make sure everything is clean when you reassemble.

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KenP

1996 S500 W140 Coupe