End bearing

[lgr]

Hello!

I have a 1970 280 SL  and it has a noise on the engine like a "sewing machine", bigger when engine is cold and, following the diagnostic of the mechanic, is from a connecting rod end bearing
As the noise as been allways there since I bought  it 10 years ago,  and to avoid spend a huge amount of money on a engine overall, I would like to know if I can use an additive like STP  to protect the engine to bigger damages and slow down a bit this noise.
I look forward your valuable comments

Kind regards

Luis Gama Rocha

[ja17]

Hello Luis,

Sounds like you may want to do more examination.   Typically engine bearing noise will become louder when the engine is hot. Under acceleration  on the road it will be quite noticeable. Eventually the oil pressure will fall off the peg even at 3,000 rpm. A bad bearing may also cause the oil pressure to dip first during acceleration before it begins to climb.  You need to do much more investigation.

Remove the valve cover and check to see if your camshaft or any rocker arms are worn badly. Make sure the valve cover hold down straps are not up against the camshaft or they will make a noise like you describe. Check the valve clearance. If any one is way off remove the rocker arm to see if it is worn. Remove every rocker arm and check them one at a time if needed.

Also check to make sure the camshaft timing is correct, in case the timing chain has jumped or is set up wrong.

Any of the above items can cause mysterious engine noises.

If nothing is found,
Drain the oil and remove the oil filter. Examine the drained oil and feel around in the oil sub pan for metal. Remove the old oil filter and break it open. Look in the folds of the filter paper  for metal particles. Remove the oil sub pan if needed. If you have an engine bearing going bad metal particles will show up in the oil filter and the oil pan.

What items have been inspected and do you have more history on the engine?

Additives in sick engine will be of little help. Running the engine with serious problems will cause additional damage. You need to find out exactly what the problem is.

[lgr]

Hi Joe
Thank you very much for your quick response and interest to my case! Now I see that it might not be from the bearing (Huf!?) because:

1) The noise almost disapear with the speed and temperature;
2) The oil pressure is allways on the top;
3) As I told you I have this car for 10 years and the noise is still the same :no worse - no better!

Firstly I'll remove the the valve cover to see if I can find somthing wrong inside and then I'll follow the other inspection steps you sugest (do you have the values for the valve clearence as well as the camshatft timing?)

Thanks
Luis
Luis

[Larry & Norma]

Might sound a bit daft but when I had a similar noise, usually at higher rpm it turned out
to be the tachometer cable! Just a thought

[GGR]

I once had a bad piston axle on a Citroen DS. The noise was similar to a bad rod bearing (krank side) but instead of increasing with rpm the noise was disappearing. It was quite impressive but one can drive much longer in that case than with a worn rod bearing, as long as he stays in the rpm range where the noise is not there. In my case 15.000 kms. Engine was still running strong when I replaced it.

[stickandrudderman]

The engine (presumably) is saying to you "I'm sick". If you don't treat it, it will die.

[ja17]

Yes,

A piston axle, (wrist pin), is always a possibility, as suggested by GGR. It may not effect oil pressure. Wisely, Dan Caron, says one way to diagnose a bad wrist pin is to remove the spark plugs one a time and see if then noise goes away. Thanks Dan.  This situation is rare. but very possible.  

Valve clearance is measured between the rocker arm and camshaft.   .003" for the intake and .007" is what I use. Rough valve timing can be checked by setting the crankshaft at "0" TDC and see if the indexing mark on the first cam holder and the slot in the washer behind the camshaft gear are aligned. Always turn the engine in the normal direction of rotation from the crankshaft. It is ok for the slot in the washer to be a little late. It should never be early when the crankshaft is at "0"

Also look closely at the steel valve cover supports. If they are too close to the camshaft, you will get a tapping noise from them.

[Benz Dr.]

Yes,

A piston axle, (wrist pin), is always a possibility, as suggested by GGR. It may not effect oil pressure. Wisely, Dan Caron, says one way to diagnose a bad wrist pin is to remove the spark plugs one a time and see if then noise goes away. Thanks Dan.  This situation is rare. but very possible.  

Valve clearance is measured between the rocker arm and camshaft.   .003" for the intake and .007" is what I use. Rough valve timing can be checked by setting the crankshaft at "0" TDC and see if the indexing mark on the first cam holder and the slot in the washer behind the camshaft gear are aligned. Always turn the engine in the normal direction of rotation from the crankshaft. It is ok for the slot in the washer to be a little late. It should never be early when the crankshaft is at "0"

Also look closely at the steel valve cover supports. If they are too close to the camshaft, you will get a tapping noise from them.

Uh....... remove the spark plug wires, not the spark plugs.

[ja17]

Hello Dan,

Sorry to mis-quote you, thats what I meant to say.