The timing chain guide replacement is not something that is a DIY job, regardless what you may read on other web forums.

Sure the average DIY guy could probably get away with doing the top three guides, but to do the job right there is also another guide on the passengers side that is shaped like a banana that is not easily seen. There are also some more guides that run off the oil pump drive chain that many fail to replace as well.

To give you a brief overview of the procedure there are two upper guides on the drivers side and one on the inner passengers side. One should remove the tensioner and followers to make the job much easier. The guides are held in by pins that must be extracted with a tool, or a home made bolt setup that uses leverage to pull them past their resistance point.

Of course before doing any of this you have to align the engine up to TDC and separate the timing chain to get the cam gears out of the way if you want to do a good job. It's also recommended at your mileage to replace the timing chain, which once all the guides are replaced must be wound/cranked into the engine by connecting one end to the existing timing chain and turning the engine until it sucks the entire chain thru. From there you would install a master link kit sold by the dealer which involves getting these tiny c-clips and a chain link together, without dropping any of them in the engine. Your first time will be somewhat painful, but once you do it a few times it wont be all that bad.

In addition to the chain, all three top rails, the bottom "Banana" rail that is used to take the slack out of the chain (the tensioner actually pushes up against this "Banana" rail) and then the tensioner for the oil pump chain. It is also a good idea to install a new OEM Mercedes tensioner after all is said and done.

Being off just one tooth will ruien your day. It seems to me that with 200,000 miles the vehicle did not sit for prolonged periods of times, which is the worst thing for these cars. In addition to rubber seals and tubes dry rotting the guides can get brittle which is one of the main reasons they break. From what you said about the engine looking real clean it sounds like your dad was a good man when it came to changing his oil every 3000 miles which is another reason you have been very lucky.

For some reason the 560's don't seem to bust the timing chain guides as often as the 420's. I think it may have something to do with the fact the SLS pump may help isolate the slop, but that's NOT to say the 560's do not suffer from the guides breaking, just that it seems to happen more often on the 420's from what I have seen. This is in no way to be taken as 560's don't need their guides changed regularly, just an observation of how often I have seen the 420's suffer the deadly timing chain disaster. I should also add that when I purchased my 560 it had been the victim of the timing chain disaster, however it was because the SLS pump seized up when some shop decided to replace the rear hydraulic rams with regular shocks, and then just tucked off the hoses to the side and paid no attention to removing the pump.

Ill post up some photos, let me know if I can be of more help, but I won't kid you, the job is rated a class "A" job in terms of skill, which is considered as Advanced.

IMPORTANT - In the photo's showing the chain being split it is important to realize that the engine we took photos of was being torn down completly, and as such there is no way you could get away with all the metal shavings as shown in the photos. Since we tore the engine down to a bare block we did not have any concerns but for someone doing a timing chain the entire area would have to be protected to prevent all of the shavings from entering the engine.

-- Edited by SELLC on Sunday 9th of January 2011 06:27:03 PM