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'85 Mercedes 300SD W126
'99.5 Jetta TDI

Get a decent looking used cam and the cam followers from a wreck. Make sure you number the cam followers as they each wear to match the cam and must go into their same respective positions.

X2 very important bit of information from Barry.

Remove the entire rocker arm towers and the rocker arms in one go - remember that the set of two are at the front of the engine.

If you have some pictures of the cam lobe wear I'd be interested to see them.

Before you fit your new cam and rocker arms make absolutely sure that the spray bar that runs on top of the cam is clean and that oil gets pumped through it!

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I was going to mention what Amy said as well. Oil feed problems to the cam are not common though on these engnes. Of course abnormal sludging or not changing the oil in the past for very long intervals might have created an issue.

Look at the face of the rockers as well. I have seen the hardened surface of the cam contact points worn though on gas mercedes. This can present a machining option to work on the lobes.

Or someone in the past doing a valve job and installing the rockers in the wrong non original placement might do this as well.

Mercedes had a real issue in the sixties with the frontal lobes on the camshafts being much softer than the others. It may have been an unequal oiling problem as well. Instead of buying all new valve rockers. I used to send the cams to Montreal. For fifty dollars including postage they would weld repair and machine the new lobes at my request. I would measure the cam for wear on the good looking lobes before sending the cam out. Put the old rockers back on all their original good lobes after the repair. Then install new ones on the repaired lobes.. Saved considerable money and the repairs stood up well.. I have no ideal what year that defficiency was eliminated by mercedes but obviously did not carry through till the 123s.

If you install the sets of rocker arms in the wrong order you can also get the rocker arm to ride its edge up against the camshaft.

Roll up! Roll up! Read all about it!

OM617 rocker arm problem?

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Thanks for the replies!

I'll see about getting the car into the garage tonight and pull off the valve cover and get some pics.

As far as replacement parts, is there a good place I should go for the used parts? Or am I stuck finding something locally?

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'85 Mercedes 300SD W126
'99.5 Jetta TDI

Being a fellow canadian I scrounge a lot sometimes. This ability to do so varies a lot between individuals. There should be a donar engine somewhere in your area.

Cam lobe failure is not high on these engines so chances are you can locate good used parts. The 123s are getting scarce on the ground on the east coast of Canada because of salt and corrosion. The cars arriving from the west are in much better condition so you should still find a donar locally. It almost does not matter how clapped out the car you find is the cam will probably still be good. Of course a junker with lower milage is usually better. Not really a hard job to take one off yourself and replace yours with it.

My only real worry when I go to do this is the timing chain and sprocket. I don't want anything to go out of whack... Like, I know my way around VW diesels pretty well for up to '06 models, and diesels in general, but the timing chain in this thing kinda scares me a bit.

Could someone give me a run down on how I should go about separating the sprocket from the old cam and aligning the new one?

Also, is the cam and rocker assembly from the naturally aspirated version of the OM617 the same as the turbo one in my car?

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'85 Mercedes 300SD W126
'99.5 Jetta TDI

Cam and rocker arms for the non turbo OM617 are different. The turbo version has about 10mm extra lift.

If you are at all worried about the timing chain set up I reckon you are better off aligning everything as described in the FSM only leaving the rocker arms off of the engine. You can then adjust and play with your cam timing to your heart's content and no piston will hit a valve.

When you are ready you can then fit the rocker arms. On my non turbo OM617 I found two sweet spots for fitting the rocker arm sets - one for the front set and one for the rear. I guess there will be similar situations for the the turbo model but you might have to fiddle about just that little bit more to jiggle everything in place 'cos you've got a higher lift cam...

...don't under estimate the effect of the timing chain tensioner on the (rotational) position of the camshaft compared with the (rotational) position of the crank.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

It is very unlikely that the chilled cast iron cam on a 85 617 wears out.
Lubrication problems would me my first bet.
It's also possible that you have the wrong cam or rocker arms in your engine.
The rocker arms have to have a brazed on carbide surface.
If they are chromed they are wrong.
The cam should have the code # 05 or 11 stamped in the back.
Is it possible that some one installed a early 617 950 engine in your car?
This engines still has the "soft" cam and the chromed rocker arms originally.

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76 240 D. Bought in 1998 for $25.
85 300D. Got it for free with a bad engine. ( Sold )
60 Unimog 404. What was left of it, was given to me. Now powerd by 617A.
88 560 SEL. Bought without engine and trans. Now powerd by 617A.
67 250 SE. Cuope. For resto or sale.
64 220SE. For resto.

I dunno if this engine got sludged up a previous life, but it was pretty clean under the valve cover when I got the car and did my first valve adjustment and oil change. And as far as I can tell, the oil rail sprays oil just fine. I highly doubt that the engine was ever changed. I got the car with 175 000Km on it and it was owned by 2 elderly couples before I got it.

I pulled the valve cover off today to take some pics.

Here's 2 that I got:




It is only the front 2 lobes that show any of this abnormal wear where there's that ridge on the edge. Also, is there supposed to be a chamfer on the cam lobes? Cause none of mine have it...

Beyond that, the other cam lobes look "ok" and are in line with the rockers. Unlike what Army had going on in the thread that was linked.

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'85 Mercedes 300SD W126
'99.5 Jetta TDI

Strange - a bit difficult to see in the pictures - the edge does look a bit weird; I can see a knick on the edge of the lobe. I wonder if that is just poor manufacturing...

...can you get a picture of the follower?

(Probably best to remove it)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

If it's the edge irregularity you're worried about, I would just deburr it and run it until something breaks, but that's me.

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Those lobes look quite usable to me. Any time excess wear is indicated just check with caliper from the top of the lobe to the bottom of the lobe. I imagine yours will be fairly simular to the others by comparison.

Nothing to get really excited about there in you pictures that I can think of yet. Even when diameter is a little less that may not be optimal but still quite useable. The small chip appearing area missing was most likely there when the cam was manufactured.

Thanks for the input guys. I'll go get a caliper and measure the lobes and see if there is truly some wear or if it has been like that from day 1. Will report tomorrow.

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'85 Mercedes 300SD W126
'99.5 Jetta TDI