So far this is turning in to a red letter day. First the problem with acceleration turned out to be just a cracked part (easily repairable!). Then while doing the valve clearances, my husband checked the timing chain and it only has ONE degree stretch. Whoo hooo! The car has 275,000 miles on it, so I don't know if that would be the original timing chain or not. Doesn't matter either way... good news!

Anyway, my question was about the cams. They are smooth, but several of them are two tone. Not sure if you can see it in the photo. Do we need to worry? Or do we just need to worry that we worry too much? The parts car was not like this.

Thanks,
Natalie The Worrier

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Natalie

Another angle..

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Natalie

That is more than likely just from old age. Maybe someone here has a better explanation, but as far as I know the only problem the early diesels had in that area is with the cam followers. Some of them were produced that did not have sufficient hardening on the contact area with the cam, and were prone to early wear.
MB fixed that problem in the late 70's or very early 80's as far as I know.

I wouldn't be overly concerned about the color. Looks a like some carbonizing from cheap oil? Cams are surface hardened and once you wear through that layer they wear out very quickly, so quickly that likely you would not catch the problem "on the brink" during a routine oil change but rather it would rattle/clank so badly you would already be looking for the problem. Adjust the valves, put it back together and enjoy it. RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

By a rattle and clink? at idle I can hear a rattling noise...although it idles smoothly...its not ueven at all. Its a rattling/ticking that never really goes away, but I never payed much attention to it..just thought it was loose stuff Under speed I hear nothing. Would this be a rattling cam? At the next GTG you gotta listen to my engine and tell me if anythin sounds wrong!

That coloring is what I call "varnish" because it resembles something called varnish that is a paint-on coating. As mentioned before, it is a deposit from oil. Not anything wrong with the camshaft metal.

I have the impression that regular Quaker State oil is famous for this. Use something specifically graded for diesel service, and I'll bet over time the varnish will disappear.

Ken300D

Kyle,
If you have ever heard a motor with a worn-out cam you'd know what I mean. The cam lobes wear down to peened over flattened nubs. The motor barely runs and makes one heck of a racket from the valvetrain clattering. I drove your car and didn't hear anything unusual. RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

Kyle, I told you not to be listening to your engine,,, turn the radio back up...

Listening too hard again. Have to turn up my music. Sorry guys!

Lots of interesting speculation going on here... but I think it has to do with the hardening process.... there are malleable cam shafts, chilled cast iron camshafts, rocker arms with carbide facing and chrome and non chrome plated cap nuts for the valves.... most of which have to go with the proper combo...
This color could easily be from " flame hardening" or the likes...

I wish all our cams looked as good as yours. That's near perfect.

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Orland Park, IL
1985 300SD 215,000 miles

Any discolouration would have been removed during grinding. Were there any discolouration after grinding, it would be caused by not enough coolant or a dull grinding wheel. Had this happened the cam would have been somewhat anealed and worn out long ago.

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1981 Mercedes 300D - 300 000 km
1980 Camaro Z28

Why would you assume it would be ground after hardening.. ? lathe ways are flame hardened after grinding.... and wheel bearings which are induction hardened have the blue in their final form...

Since the line between the two colours is perfectly straight and even, and appears perfectly centered (didn't actually measure), it seems to be it would be more likely caused by the manufacturing process, or by wear. Since only 3 of the 5 are like this, I was thinking more likely wear.

But, maybe it's nothing to worry about. I'll move on to worrying about other things. :p

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Natalie