I have a 1997 E300 with 184K mi and it runs good (no smoke, starts right up) except it has a small water leak at the back of the head. Water drips onto the exhaust pipes and about once a month the radiator low water light come on and I have to refill it. I have been operating this way for about 6 months now and since I have 2 weeks off for xmas I plan to do R&r the head gasket. I plan to check the head, check the injectors, remove and clean out all the glow plugs, then put it all back together again. I purchased alldatadiy so I have the instruction from that but I still have a few questions. Below is my current quesiton but will take advice from anyone that has done this and has some tips to "watch out for".

Can anybody tell me what exacetly to do with the chain tensioner (not talking about the guide rail). The one on the front left of the engine. Do I just pull it out? Can I reuse it or am I suppose to get a new one? How exactly do I fill it back up with oil and how do I install it. alldatadiy says to

INSTALLATION

• Replace chain tensioner only complete. What does this mean? Only install it assembled? Replace seal (8).
• Before installing, fill chain tensioner with engine oil. Place chain tensioner with the thrust pin facing down into engine oil until it extends over the collar on the hexagon. what does this mean? Are they talking about how to fill the tensioner with oil before installing?

Press thrust pin through slowly 7-10 times as far as the stop with the aid of a press or a column-type drill.

NOTE: After filling, it must be possible to compress the chain tensioner only quite slowly, evenly and with considerable force.