1996 S500 (w140) timing chain

Your engineer is a little mistaken.

The chains stretch over time. Then the tensioner can't adjust for the stretch. Then the chain starts flopping and breaks the plastic guides. Usually the first rail to break is on the left side, inboard at the bottom of the head. Then there is so much slop that the chain jumps teeth, usually on the left head 1st.

Average life span is 100K miles.

Three choices: repair this engine - new / rebuilt cylinder heads, cams etc. or buy a used engine from a salvage yard that was in a wrecked car and have its timing chain replaced before that motor is installed in your car. A 420 V-8 might also fit (check before proceeding) and that would enlarge the choices of available used motors.

If you really want to keep the car for a long time a M-B or independent factory rebuilt motor is a third, more expensive alternative. see

Thirty-three *thousand*!?! My goodness, you could buy a newer car for that much. Thirty-three *hundred* sounds high for the top end of this engine (remove & replace valves both heads). I would get another estimate, this mechanic clearly has a boat.

He was wrong, it's one of the major deaths of Mercedes engines.

Get a good used engine. CHange the timing chain, oil pump chain and oil pump. Have the heads done. Good as new. for I'd gues about 4K.

Richard Sexton wrote: > He was wrong, it's one of the major deaths of Mercedes engines.

Oh, damn - if he would even have hinted at the possibility of the bloody thing breaking, I would not have hesitated to get it replaced.

I hope this is not a naive question, but would it not be cheaper to replace valves and cylinder heads in my current engine?

G.

The 8 cylinder models have it worse but you shuold still have the stretch measured. With regular frequent oil changes the chain should last longer but they all need to be checked and replaced at some point. 68K isn't quite worth worrying about yet though.

Yeah no kidding. He didn't do you any favours.

These are interference engines so the pistons invariably contacted the valves meaning new pistons and rings - and you relaly can't bore out these engines as they're made with silicon impregneated aluminum; when the aluminum is ecthed away only the silicon remains on the cylinder walls.

If all 8 of the pistons are clean then you could get away with it, they should be able to use a boroscope to check, but don't count on being able to reuse them. THe other problem is if the piston mashed the valve around and bits scarred the engine bore then it's, sadly, scrap now I"m afraid.

IS there some simple way to check the timing chains for stretch or do you have to do a lot of disassembly to do an inspection ?

Turn the right cam with a wrench clockwise so the chain tensioner fully seats and hold it there. Now try to lift the chain up over the teeth of the right cam, on the left side of the gear. If you can move it a tooth, it is time to change it.

"Engineered like no other car in the world!"