Both gas and diesel Mercedes engines have a chain driven camshaft. Your question could be answered in this "Tech" Section. But since you have also mentioned the vacuum pump issue, I think you would get more response from the Diesel part of the Forum. Just do a search on either part of your question and you will probably come up with more to read then you have time for. There are specific ways to check the chain to see if it should be replaced and basically if you change it with the head gasket job you might save a very little labor, but not much. I think the same can be said about the vacuum pump and the head gasket. Save a little, not much. However, if in checking you find it might be the time to change the vacuum pump, that might be a good time to lay in a new timing chain, but again only if it needs it. Check the "Diesel Section". You will get plenty of information.

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Junqueyardjim
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1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
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