M115 valve gear CLATTER

[nachi11744]

Hello,
I know that most of you guys have or had sixes or V-8s, but I still have to ask this. My W115's M115 has an annoyingly loud valve clatter at around 2500-4000rpm inspite of the lash being correct, above that speed the general din of the cooling fan and wind noise tends to drown out the clatter
I know that the Mercedes gasoline engines (M114,115,121,130,180) that use this type of valve gear are not known for silent operation, but is there any specific wear point or adjustment *trick* that I am missing here?
Performance and fuel consumption are not affected, the car pulling 90mph easily and slowly easing up to almost 105mph(checked against highway markers and stopwatch)
Thanks in advance.

[Oreo]

Nachi

I used to hear a light ticking sound from inside the car that I assume is from my valve train too. I don't want to start another oil thread but the sound went away when I used synthetic oil. The noise was very soft so I didn't make a big deal about it with the synt oil.

Oreo

[300SDog]

Then it sounds like one of your valves is sticking a little bit or maybe a valve guide is scored.

Otherwise, if its alot of clatter instead of just ticking then it could be the timing chain slapping against the rails on account of a weak or maladjusted tensioner. 4 cylinder engines always seem to clatter more than the 6's.

Also, I can remember finding a few dislodged rocker arm hold-down springs on one of my 220Sb's.

Synthetic oil made a believer out of me in the diesel which really needs the slippery stuff to make the engine more startable in the cold. It improved accelleration too.

[nachi11744]

Hello,
The noise is a distinct valvegear clattering, like a dozen little hammers banging away.
Chain is tight when I checked it cold and hot, how do I ascertain if it is tight when the engine is actually running without getting covered in oil?
I will look at the holder clips and the oil pipe to see if anything there has broken/slipped off/blocked etc.
Thank you.

[300SDog]

Nachi, if that is multiple clatter that sounds like 8 tiny hammers rattling away in symphony then there might be no problem.

Meanwhile if it's isolated tapping tracable to maybe one cylinder then it could be sticking valve, scored guide, bent valve stem, etc.

Otherwise racing the old 4 cylinder (with how many miles?) at top speed could have even rounded and roasted valve seats in addition to bending a couple of stems where guides are worn.

Maybe a stethoscope will tell you if its normall rocker arm chatter or if it's toasted valve seats or valves seating unevenly that are making the clatter as they round off otherwise flat edges on valve seats.

Oreo, i believe that synthetic oil purges varnish from stems and guides making the valves less sticky in their guides and thus reducing the clatter of rocker arms too - as the rockers arm cups then wont bounce so much off the acorn nuts.

Diagnosis based on MB valve train clatter and chatter requires musical ear - and i'm no expert - but I've heard that only one cylinder head rework is allowable per alloy cylinder head, say at/near 125k miles to enable the block and engine to mate in their clearances and run forever.

Probably the last thing you want to do is overtax tired crank and conrod bearings by refurbishing the cylinder head and valve train at/near 200 thousand miles without at least selecting an extra thick head gasket to reduce compression...... assuming that double thick head gaskets can be found.

[nachi11744]

Hello,
I have a clue, there is a slight missfire at cold idle, something has got to be sticking I will do a lash adjustment this weekend(hopefully)and then listen attentively Keeping my fingers crossed that it is not a seat or guide
Thanks for the pointers.

[nachi11744]

Hello,
I have done the valve lash adjustment, it was all the valves slightly loose, the previous adjustment was done by my indie tech and he seems to have set the lash on a cold engine to the hot specs. I think he has not had to do a valve lash job on any Mercedes for the last ten years, what with all the hydraulic lash adjusters in the 1980s---- engines. Should have given me a clue when he had to *borrow* the crowfoot wrench from me to do the work, his has been *lost for years*(his words).
Have a good week.

[Oreo]

Hi Nachi

When I did my valve adjustment for the first time in this car I wanted to borrow my mechanics feeler gauges (he has become a friend). Guess what? He did not have the right sizes, especially for the intake. So it led me to think that most shops don't bother with individual model specs, they just use a generic gap size. All my gaps were a little loose.

Oreo

[autozen]

Rebuilt cams are generally noisier than stock cams. Has your cam been rebuilt or replaced with a rebuilt?

Peter

[nachi11744]

Hello,
The cam has the *05* and tristar emblem on the end bearing, so it is stock.All the clearances were 0.05mm too wide, intake was 0.15mm when it should be 0.10mm cold, exhaust 0.25mm when spec is 0.20mm cold. There is much less clatter now, but these engines are not know for quiet operation
The M117 500SL engine with hydraulic tappets is less noisy with double the number of cylinders
Have a good week.

[autozen]

When I said stock I meant it hasn't been rebuilt or reground. Your cam could have been reground.

Peter

[300SDog]

Autozen, Have you seen rebuilt camshafts successfully installed on any Vintage MB's?

There used to be a legendary fellow named Iskinderian (sp?) at Arizona who was famous for grinding 1/2, 3/4 and even full race camshafts for street rods. Yep, here's his shop on the internet: http://www.iskycams.com/

About the only MB camshaft problems I've ever seen were on my twincam 280/8...... something like 3-5 exhaust lobes were worn down and several intake lobes too. Symptoms beyond a clattering racket included difficult starting, rough idle and poor low rpm engine performance. The wear was clearly visible and naturally the rocker arm tops were worn down too.

I wonder if the rocker arms wore beyond their surface glaze before the camshaft started wearing away? This might be something that twincam 2.8 owners should keep an eye out for.

Repair work for me involved replacing rockers, camshafts, carrier and sprockets with pick'n pull junkyard parts.... LOL, I was the 'hero' at the junkyard that day - and the junkies treated me with respect for spending a few hours and pulling the parts by myself. I think it was $50 for all the parts.

Meanwhile everybody who gave me advice on this project, parts people and independent mechanics, told me that 'rebuilt' camshafts where metal was added to the original lobes and then reground was a bad idea and would never last.

Also somebody here, TomGuy i think, found a set of Euro-sloped camshafts in a junkyard car for souping up his 4.5 that he identified by translating the hieroglyphics, letters and numbers on the end cap.

[nachi11744]

Hello,
No machine shop around here can regrind cams, usual way to remedy any wear was NEW parts, nowadays USED parts. The DC dealers do not supply rebuilds either, only new parts.
In any case, the clatter is *almost* gone when running at 3-4000rpm, slight ticking only around 2-3000rpm, I can live with that.
Have a good weekend.

[autozen]

240,
No I have noy had any success with rebuilt MB cams. I tried it many years ago and found them to be much noisier than a new or used cam, which is why I asked the question. Comments by parts people and mechanics gave you good advice. I had a cam lobe rebuilt where they added material to the lobe and reground whole cam. It never made it out of the warrantee period before the material fell off. The cam was junk.

Peter