Timing chain tensioner: Before you can pull the tensioner, remove the AIR pump. Or at least, pull the top bolt on the AIR pump, loosen the bottom one, and slide it out of the way. Of course, you need to loosen and remove the serpentine belt. I recommend only removing the belt at the the motor and by the AIR pump pulley. It’s very easy to reroute the belt incorrectly and strip out your belt tensioner rod. I’ve done it! Thankfully, not lately On the end of the tensioner is a hex “cap”. I think it’s 10mm. Loosen this a couple turns before pulling the tensioner (27mm socket). With the tensioner in hand, you will want to remove the cap, and with a ¼” entension put in the side of the hex cap, push the guts of the tensioner out toward what was the engine side. When it’s time to install the housing and “reload” the tensioner, ***be careful*** you don’t crossthread the tensioner housing like I did. It should almost thread in by hand. So, with the guts out of the tensioner housing, and a new or good condition alumimum O-ring on the housing, thread in the tensioner housing. Don’t tighten down all the way. Then, insert the “plunger” first in the hex/cap side of the housing. With the ¼” or 3/8” extension in the housing after the plunger, push down on the plunger until it seats. You’ll feel it. You’ll need it pushed down in the housing to install the spring-loaded cap. Then, insert the spring, the cylinder that sits in the middle of the spring, and the cap. Be aware there is an alumimum O-ring washer that also fits/seats down inside this hex cap. You might consider replacing this too. I used a ratchet/hex socket or an allen wrench to do this. Kind of tricky, with the spring tension against your hand. With the cap seated/tightened, I then torqured the tensioner housing. It will seat at 59 foot lbs. The cap is much less. Again, make sure you’re not cross threading the housing. I lost two+ quarts of oil on the garage floor and about ½ day because I didn’t realize mine was cross threaded. Thankfully I was able to save it and get it rethreaded. BTW, don’t install the tensioner until you have the head back in place and torqued down, and not until your timing gears are aligned with TDC, and the chain is on properly. With the tensioner in place, and everything aligned correctly, I then tighten/torque down the bolts on the cam pulley.

Putting it back together is the easy part.
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Before you tackle the job, order these parts:

· two vacuum hoses that attach to the bottom of the intake – approximately 3/8” ID on the hoses (about $12 together)
· heater hose (attaches to the heater core outlet behind the master cylinder, and to the back of the cylinder head/block (driver’s side) --- I also had to use another hose clamp at the block,, as I destroyed my clamp removing it from the engine. - $18
· head bolts (you don’t need the washers that are upsold)
· aluminum washer/o-rings for the timing chain tensioner --- good to have a spares (there are two sizes – one for the cap on the end of the tensioner housing, and the other for where the tensioner threads into the block) – couple bucks each
· head gasket kit – upgraded style gasket (contains all the little o-rings and things you’ll need
· valve cover gasket (if needed – I replaced mine last year, so I knew mine was in good shape)
· valve cover grommets (key for stopping valve cover leaks – fit under the washers on the valve cover bolts) – old ones get flat with time, which don’t allow the valve cover to seat correctly
· MB coolant
· MB sealant – front cover, or if you replace the valve cover gasket
· Water pump --- there is NOT a better time to replace a water pump, especially with the intake manifold out of the way
· Guide pin for driver’s side timing chain rail (you pull this when you remove/install the front/upper timing chain cover)
· 27mm socket (crankshaft bolt – turning the engine over by hand) and the timing chain tensioner) – can get this anywhere
· variety of 6/7mm hex/allen sockets/wrenches and extensions – for tight fitting/slim access to hex bolts
· socket (XZN socket for the head bolts. I bought a set of these at pep boys. They are 12 point – and they portion that extends out of the socket needs to be long enough. They sockets don’t need to be stubby.

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In closing, I tackled this job after piecing together the majority of my knowledge (buried in old posts) over a two month period. But I still didn’t forsee some of the pitfalls I experienced, most of which I attribute to my failures as a MB mechanic. So, I really tried here to explain, in laymans language, what this job entails.

I could do the job again in ½ the time. And, in retrospect, had it not been for me (a) not having the head bolt socket; (b) not having the new head bolts, vacuum lines that attach to the intake, heater hose that attaches to the head/block, aluminum washers for the chain tensioner; (c) not cross threading the tensioner housing; (d) not breaking the vacuum attach points on the bottom of the intake --- I’d have been done much sooner.

Thanks especially to Mbdoc, ILUVMILS and Arthur Dalton.

71Rcode