Oil Pressure Low Suddenly

I was caught in a slowly moving traffic jam, when I looked a the gauges to check engine temp. and found oil pressure a 0 when inching forward, and 0 at idle. pressure would rise to 3 when accelerating,
then promptly drop to 0 until the next move. I checked the oil, (1 quart low) added oil.....no change. At start up pressure is 2 when idling, after driving for 10 miles pressure drops to 0 at every stop light I do not ever recall seeing my oil pressure at 0 in the 10 years I have I have owned this 1992 190E 2.6 with 138,000 miles (that does need head gasket repair) 1 quart in 500 miles leak when last checked (no oil in coolant) Thank you for any advice........Rick
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Hopefully it's just a bad pressure sending unit. Since you are adding a quart every 500 miles, are you changing the oil and filter on a regular basis? If not, the oil filter might be clogged. Also, it's possibly the oil pump pickup is jammed with sludge and other debris (and this might be leading to oil pump damage) if the oil is not being changed on a regular basis.
Josh
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Thanks for the replies guys I never thought of the sending unit. I was thinking my leak had greatly multiplied in size, or oil pump failure, I will check that possibility also. Regular oil, and filter changes have been performed every 3,000 miles . Is there a good way to desludge an oil pan ....just in case ?..... The car really needs a good 600 mile high speed road trip. Thanks again....Rick
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That just reminded me, I have a 1993 190e 2.3 and it uses about a quart of oil every 1000 miles or so. I can't find a leak and the oil and AF are clean. No smoke to speak of.
But the big problem with the motor is a knock. I can't tell where it is coming from. It does it all the time, more so on startup and when it's cold. And it get's quieter under load and is louder at idle or coasting.
To me it sounds like a rod knocking, but the MB mechanic said that the bottom ends never go out of these. And if it was a rod, it would have thrown it by now, it's been doing it for a few thousand miles now.
What else could it be ? Wrist pin bushing? Bearing? Sounds to low and far back to be a lifter of timing chain tensioner.
Any thoughts? Oil Pressure and compression are good btw.
Thanks

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I have the same problem on my 89 190 E 2.3 have to add oil every 1000 took to mercedes shop replaced valve guide . no more oil low after valve job done
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