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  #1  
Old 01-01-2011, 08:54 PM
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adjusting rocket arms

I have a 67 250 S M108

There is a noise in the engine and my mechanic said one of the roller rocker arms needs to be tightened because he can hear its lose.

I just got this car and I never worked on MB. Can you guys give me some pointers on this?


Thanks,

Laszlo

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  #2  
Old 01-02-2011, 10:50 AM
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Arm yourself with a 28mm socket, small extension rod & breaker bar so you can hand rotate the motor. Also get a set of feeler gauges. Ideally one that's calibrated metric.

Remove the rocker cover (three bolts on the top). The hose from the power brake booster should be in the way. remove the connection on the booster.

There's a permanent gasket on the bottom of the rocker cover that you'll put back on later. If you don't have an oil leak dripping on the garage floor, the gasket is probably fine. But now's the time to take a look at it.

You should see the row of rockers, some pointing left and some pointing right. Each one should have a coiled spring holding it down. See if one is missing or disconnected from the retaining clip that holds it to the rocker stud. A pair of needle nose pliers can be used to reattach one that popped off.

You'll see some rockers are pushed down by the cam and others are not. The ones pushed down by the cam will be solid. The ones not pushed down will have a little bit of wiggle room, but not much. While you're looking, is there a bad cam lobe?

Now you can rotate the motor through a full revolution. Do the turning so that the chain comes up past the chain tensioner (it's on the side with the exhaust manifolds).

Do it a bit at a time and wiggle the rockers that are not pressed by the cam. This is not at all a rigorous test; get out the feeler gauge. Find the right feelers for valve clearance and also one that's the next larger size. They should be a bit oily. Also they should be free of grime.

As the cam rotates the time/place to check the clearance is when the pointy part of the cam lob is pointed away from the pad on the rocker it rotates through. Also, you need to figure out which ones are intake and which ones are exhaust. Eyeball where the rocker is relative to the ports on the intake and exhaust (That's easier than remembering EII EEII EEII E; something you yell when you bust a knuckle ).

To actually change the valve clearance, you need a special open-end wrench. That's not the kind of thing you pick up on a Sunday, so don't worry about it. Also, don't rely on memory, write down the clearances on a piece of paper.

To put the rocker cover back on, wipe the mating surface of the head a bit to clean up any grime/oil that got in. Lay the gasket on the head then put the rocker on the gasket. Some wiggling is required to get it to slip in the grove and then seat.

Don't over-tighten the bolts that hold it down. When you reattach the brake booster line, don't over-tighten that one either.

-CTH
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Old 01-02-2011, 12:52 PM
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Laszlo,

You need a special wrench (14mm or 17mm) to adjust the rocker arms. The noise could be happening because your rocker arms are loose. It could also be worn rocker arms and/or ball stud assemblies. The rocker arms open and close the valves, and the procedure for tightening the rocker arms is called a valve adjustment.

How mechanically inclined and experienced are you? Do you have the tools required? Do you have a manual that tells you the correct valve clearance? Do you know which engine is in your Mercedes? Is it an M127 or an M129 or an M130?

Can you get your mechanic to do the valve adjustment and let you watch? You also want to look at the rocker arms and ball studs to see if they are worn. Are the ball studs 14mm of 17mm?

Your profile is not filled out... Where are you from? If you are in Houston, Texas I would be willing to show you how to do it.
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Old 01-02-2011, 01:03 PM
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Quote:
Originally Posted by cth350 View Post
Arm yourself with a 28mm socket, small extension rod & breaker bar so you can hand rotate the motor. Also get a set of feeler gauges. Ideally one that's calibrated metric.




-CTH
Are you sure about this size? Most MB motors use 27MM on the crank bolt.
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  #5  
Old 01-02-2011, 06:09 PM
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It is a 27 mm and I think the ball stud are 17 mm. Valve adjustment isn't too hard to do until you find a ball stud that won't move freely - which will be just about all of them.
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  #6  
Old 01-05-2011, 02:02 PM
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I have been messing arund with my old Chevy so I know a little. I always thought working on european cars will be pain. I have my benz for a month and a half and I'm very impressed with the design and how everything is working and fitts on a over 40 years old car.

Thank you all for the advise I think I got it. Hopefully this fixing will take away the lawn mower sound of the engine..

Quote:
Originally Posted by JeffreyNMemphis View Post
Laszlo,

You need a special wrench (14mm or 17mm) to adjust the rocker arms. The noise could be happening because your rocker arms are loose. It could also be worn rocker arms and/or ball stud assemblies. The rocker arms open and close the valves, and the procedure for tightening the rocker arms is called a valve adjustment.

How mechanically inclined and experienced are you? Do you have the tools required? Do you have a manual that tells you the correct valve clearance? Do you know which engine is in your Mercedes? Is it an M127 or an M129 or an M130?

Can you get your mechanic to do the valve adjustment and let you watch? You also want to look at the rocker arms and ball studs to see if they are worn. Are the ball studs 14mm of 17mm?

Your profile is not filled out... Where are you from? If you are in Houston, Texas I would be willing to show you how to do it.
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  #7  
Old 01-09-2011, 03:52 PM
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Hey guys thanks again your replies was helpful but since I didnt have the special tool to loosen up the adjusting bolts I got stuck there. I even bent my regular 14 inch wrench but the bolt would not give.

So what kind of wrench would do the job?

Thanks in advance,

Laszlo
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  #8  
Old 01-09-2011, 09:13 PM
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Looks like this...

-CTH
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