My 86 420 SEL has a constant tapping noise from the top end of the engine. By looking through the oil cap hole I can see that my camshaft oiler plastic mount is cracked. I suspect that the same is true of the other side of the engine. The camshaft has no grooves in it and the lobes are shiny(normal?). Will these camshaft oilers being faulty effect the oil pressure ??? My gauge reads perfectly all the time according to my manual. The coolant temp is also normal all the time. The engine still runs very smoothly. The reason why I think the plastic mounts are just leaking and are probably not the main source of the problem is because the engine oil pressure is perfect and the top end of the motor is getting oil. Is it fair to say that the noise may be a faulty lifter or rocker arm ? Any input or info would be appreciated. THANKS

How many miles on it? The tapping could be a lifter or rocker arm or camshaft. Did you pull a valve cover? The cam can wear on the back cylinders so that the cam looks good through the oil filler hole, but is worn out. I am not sure but I think the left rear ones are the furthest from the oil pump so they get oil least and last. This is done by plastic tubes and theycan clog as well. The lifters can be shimmed and I was told they almost never go bad. Most unlikely a rocker arm. My unskilled 1.5 cents.

Steve
'85 500SL (Euro)

The car has 88,000 miles on it. The sound is clearly coming from the drivers side. Any more input would be appreciated. THANKS

Sorry I forgot to mention this but would the tapping sound be the same if it was a camshaft, rocker arm, or lifter or do they each have a distinct tone ? THANKS

What you describe sounds like a hung lifter. All of the other things you describe could produce some noise, but would also produce a performance hit as well, ie cam lobe worn. If there is no perceptible miss, I would suspect a lifter. Try to isolate the offending cylinder and check those valve train components.

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

On this engine is is RARE for a lifter to fail. If one of the oil rail retainers is broken, it may have starved for oil at some time. If this happens, the rockers will fail. Have the rockers checked and replaced if needed.

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Benzmac:
Donnie Drummonds
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

THANK YOU for the replies. I agree that it is probably not a lifter. How many hours of labor is it to change the oil rail retainers and rockers on both sides of the engine ? Just out of curiosity if the camshaft and rockers were significantly damaged what would be the symptoms ? THANKS again

I will be taking the car into the shop soon and I'm wondering if the camshaft MUST be replaced when doing the rockers because they must be done at the same time on the 300 SE/SEL. THANKS FOR ANY MORE INPUT

The cam should be visually inspected, same with rocker arms and valve stems. Cam lobes are usually miked for excessive wear and loss of lift. If cam is worn or rocker arms are damaged, there is usually a loss of performance that may or may not be noticeable depending on the degree of damage. Make sure the dealer is clearly able to detail the exact problem before you sink a ton of cash into the repair. If it's the rocker arms/oilers have them show you the problem. Same with the cam. You describe a smooth running engine, so I'm still leaning towards a hung lifter. At least for your sake and your wallet. Hope it turns out OK.

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

Is this an excessive amount of damage to an engine with only 80,000 miles? Are you changing the oil frequently?

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'89 420 SEL
'90 300 SEL
'84 300 SD (sold it)

NEVER and I mean never did I drive for more than 3500 miles without an oil change. THANKS for any more input

mattsuzie,

I understand your comment, but even with frequent and religious oil changes, and even on a Benz, stuff happens.

Larry

THANKS for the replies everyone. Can someone please explain the R&R for a rocker arm. Is a valve spring compressor necessary for this job ? THANKS AGAIN

George, valve spring compressor is not needed if you are replacing rocker arms. Only needed for actual valve work, i.e., seals, springs and the like...BTW, did you get a definitive diagnosis yet..sounds like you did..

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

[This message has been edited by jeffsr (edited 08-17-2000).]