Doing my 1st valve adjustment on my '81 240d. I tried rotating the engine by the PS pump per the Dieselgiant dvd but the belt just spins, not turning the engine. After searching the forum here others suggested using the crankshaft bolt. Stupid question-WHERE IS THE CRANKSHAFT BOLT? The haynes manual was no help and I haven't found an engine anatomy lesson here yet. If it's on the engine front there's little room to work. Any tips/tricks to doing this?
Also, Want to check the chain stretch while I'm in there. I found where you line it up for TDC but where is the numbers/marker at to determine the degree of stretch? I've seen the pics on here but where is it at on the engine? Any help appreciated, JEFF

The crankshaft bolt is indeed at the front of the engine and yes, it's a tight fit. The nut is in addition "recessed" inside the crankshaft pulley so it's as hard to see as to get a wrench on it. It's a 27mm, I believe, and a deep socket on a 12 inch ratchet should fit. It's probably necessary to do the turning from under the car while someone up top watches for TDC.

If the PS pump belt slips, it is probably too loose and/or old/worn. Tightening and/or replacing the belt may help. A remote starter switch that allows you to "bump" the engine can also be used, carefully, to advance the engine one valve opening at a time. I have done that; it's a lot nicer than fighting with wrenches in tight places.

You measure cam chain stretch at the timing marks on the camshaft, at the front where the first bearing is.

Jeremy

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be sure your motor is in N if it is a standard transmission...
I find it easier to pull the glow plugs when doing the valves, no compression to fight this way...

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Taking off the fan and shrowd really isn't that big of a deal.
You can also use a deep socket if you have one.

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1982 300CD Petrol/Black Leather

Thanks everyone.

I use a remote bump starter device that clips on to two screws located in a small black box near the battery. Just pull the trigger after you have it hookrd up, it will engage the starter, you have a lot of control as to how far the engine rotates. I use it to mount v belts too.

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83 SD

84 CD

I just used a big wire. The remote part is only necessary if the connections aren't easily reachable. Works great - I can't imagine removing glow plugs or fan shrouds - why bother?

Edit: I guess the remote aspect would be handy when replacing belts, unless you have three really long arms.

I've bumped the engine before, but I find I get better placement turning it manually.
If I were on the clock, I would probably bump the starter.

I had a bad/loose belt when i did mine also i found by pushing down on the belt while turning the pump gave it enough grip to turn the the moter.

I use the steering pump nut. If you get to a spot where it just wont move anymore, push UP on the belt from the LOWER side while trying to turn the engine. I found using the crank bolt is a PIA.

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1985 Euro 240D 5 spd 140K
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Last three valve adjustments I've just bumped the engine. There's 8/10 lobes, chances are one is pointing upwards after every bump. Good luck!

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Tomas, Sweden
1966 Mercedes Benz 230S with OM617.912, automatic. Disk brakes from W108
1983 Mercedes Benz 300TD grey, OM617.912 and 5-speed manual
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That works, anything to make a connection, just more control with a switch.

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83 SD

84 CD

It's not worth doing just to set the valves, but having the injectors out really makes it cake if you don't have bent wrenches. If you can find an excuse to do something with the injectors (pop test, clean, replace, admire), by all means do the valves when they are out.

Rick

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