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Old 04-12-2002, 10:26 AM
johnp352 johnp352 is offline
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Join Date: Jan 2001
Location: Naperville, IL
Posts: 32
E420 bizarre oil gauge behavior (no really)

Here's the situation..94 E 420 with 103K. I bought it with 92K in 1/01.. When warmed up, the gauge used to read 1.4 bar or so. After last summers big heat, the pressure dropped to 1 bar (by "dropped to" I mean I would drive it on a medium heat day..45-65 degrees..say a long hiway ride..then get stuck in traffic, where it would do this). After changing the oil, the pressure would be ok, back to 1.2 or so after this sort of driving- but 500 miles after the change (10/40 w) it would continue to be low. Now it is below 1 bar, around .7 or so (I can't really be to exact here) after a long drive, then at idle in D.

So far, seems like the average "You are worried about nothin" V-8 mercedes newbie post, right? (and that description would describe me...) -the gauge pins at around 15-1800 rpm and stays there on the hiway, though after reading all the stuff here about what that doesn't seem to "pin" as much as hesitate a bit then get up there...

But- here's the strange thing: when I am idling at a stoplight, car in D, pressure at the 1 to .8 mark or so..and I turn the wheel a hard right or left..without moving, just turning the wheel..the oil pressure gauge dips..then pops back up.

my friend, a merc mech at Laural here in Chicago, said he has never heard of this- and that it sounds "like an electrical problem"..

so, are there 2 problems here..a mechanical /oil pressure thing, and an electrical/harness problem too? allright!

I have read the 1,298 posts here about oil pressure gauges, oil weight, synthetics vs non, oil pressure sensor, etc etc and not found any mention of this.

So, assembled Merc Massive, how to go about this in a logical order? my mech (Master class Mercedes guy for 12 years) says Synthetic is a waste of money, just try 20/50.

does a plan like first trying 20/50, then synthetic, then changing the oil pressure sensor..then taking out a second mortgage to pay for Merc shop diagnostics seem the right way to go? i guess I just don't understand why the idling pressure would change so much after only driving the car 10,000 miles..

thanks for any help.
John Pazdan
94 E420
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