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Having had the oil pump on my W201 have a catastrophic failure as seen in this post: http://www.benzworld.org/forums/w201-190-class/1522054-head-removal-2.html#post4168434 Granted this is the M102 engine and the oil pump is a direct drive of the crank, quite different than the M116 in my 420SEL.

So needless to say, I am quite sensitive to oil pressure in my W126, as I certainly do not want to experience another oil pump failure.

I noticed the other day that at idle with the engine at operating temp the needle on the oil pressure guage would "wobble" or more correctly "dance" right around the 1 BAR line. is this normal? Or should I be getting prepared now and go ahead and replace the oil pump, or is it just the sender?

TYIA
 

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I believe mine hovers at 2 bars at temp. I will check it out today. Not sure if there is a difference between a 420 and a 560.

Mike
 

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What do you mean by "dance". Oil is viscous and cannot not change in pressure quickly so a needle that bounces or dances is indicative of a problem with the sender. Mine had a bad terminal lug on the wire such that engine vibrations and a stiff and short wire caused it to "dance" the needle..
 

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By the term "dance" I mean that it tends to vibrate up & down rather quickly from just above to just below the 1 BAR mark. when driving it holds steady at 3 BAR and only drops at idle.
 

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By the term "dance" I mean that it tends to vibrate up & down rather quickly from just above to just below the 1 BAR mark. when driving it holds steady at 3 BAR and only drops at idle.
Our 300 SEL does the same thing. I have no idea what the problem is, but it doesn't worry me, unless I see that needle drop all of a sudden...
 

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Landscape,

Finally remembered to look at the oil pressure gauge.

Here is my data (pay close attention to the RPM's)
When @ idle in "D" i have a solid 2 bars.
When in "P" I have roughly 2.25.
When @ normal driving speeds it pegged @ 3 bars

I had that dancing oil pressure but my idle was surging as well. I tuned it up and adjusted the A/F mixture and my surging went away.

Mike
 

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My 420 SEL used to do that. Local Indy said said that as long as it pegs under acceleration I was fine. I swapped out my my gauge cluster when I did my interior swap and the new oil pressure gauge smoothly moves and stays steady wherever it needs to be. I conclude that the bouncing/dancing was a bad gauge in mine since the "newer" cluster fixed it.
 
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