I've thoroughly searched the forums and can't seem to find a definite answer to this question. I purchased my '98 S420 a few months ago with 118,000 miles on it and I don't know if the timing chain has ever been changed. What is the recommended interval for timing chain replacement on this engine? Should the guide rails be replaced as well?

I know a rule of thumb on the 126 V8 S-classes is to change the timing chain and guide rails every 10 years or 100,000 miles, but those are the 116 and 117 engines.

Since a timing chain job is beyond my technical capabilities I would have to have a shop do it. Any idea as to what it would cost?

MB hasn't issued a replacement mileage on any engine.
They do suggest inspecting the chain any time the valve cover(s) is off.
On a diesel engine 3-4 deg stretch is max & on a gas engine 5-6 deg.

On that engine you would check for stretch at 45deg BTDC compression stroke.

Have seen M119 engines with broken chains at 125K & others with good chains at 200K.
Guess that depends on oil change frequency...?

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The M119 in my E500 has the original chain at 200k.

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1994 E500 199/Gray 82k
84 300D (Salty) Orient Red/Palomino 141k
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88 300CE Brabus 3.6 199 on Black 44k

I thought M119's have a ratcheting tensioner, like the M104 engine, which should eliminate the timing stretch problem that M116 / M117 engines have. M116 / M117 engines have a tensioner that relies on oil pressure, meaning there is no tension on the chain at start-up.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".