I am thinking about replacing the upper chain guides on my 400E. Does anyone know if a special tool is required to get the old ones off or is it an easy job?

I have heard stories about the plastic guides disintegrating, resulting in a jumped cam sprocket and possibly bent valves. I asked an experienced tech about this and he said that it was more common in the older engines, but he's never seen a 119 jump a sprocket. Has anyone seen this on a 119?

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

There is a special tool to remove them, designed for removal w/o breakage.

MOST of the time they break anyhow. If you are replacing them make sure not to allow pieces of them to get into the engine.

YES timing chains can jump on the M119 engine, have seen at least 10 with bent valves & broken camshafts.

The tensioner is always at fault.....lack of oil changes are the most probable cause of tensioner failure!

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do these exist in the M104 engine? Is there anything in there that requires service other than an oil change every 3500 miles or so? I have about 105,000 miles on the car as the original owner and its been carefully maintained and not abused.

I have seen 2 with bent up valve train issues. I purchased one of those (as junk) for a rebuilder, finished it about a year ago.

On newer 119s these plastic pieces lift right out after you remove some of the cam journals etc. The tensioner is always a pain, but it should be done. It's not that the spring loses elasticity, but more like wear around the chain face that turns into other [big] issues. 30k mile oil will do it nicely.

It's almost always neglect, like Pat said. For those just getting into the now-affordable 90's S-classes, remember "The 140 is the most unforgiving machine on the planet of neglect and ignorance"

104 motors do have chain guides - I think just 3, upper, lower left and lower right. 104 motor chains seem to be awfully strong. It's a double row chain, as is the 119, but of course a much shorter path. You just don't hear about them being a problem.

are the guides something that i should consider having changed out at 105 k miles? Does head have to be pulled to do so?

Thanks, all. I guess if you're not putting the old ones back on, it doesn't matter if they break coming off, as long as the pieces don't fall into the engine.

I change oil every 2,000 miles and I haven't heard any "rackata" noises coming from the engine yet; but I'd like to change the tensioner too. I still need to get the special pin (111 589 03 15 00), so the exhaust cam doesn't jump across when the timing chain tension is relieved.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles