Hi All,

Having a recurring problem with my 1995 E320 Wagon with 243k miles. She runs like a top, has full service history from 1,200 miles, all the regular stuff has been fixed/replaced, and then some.

Anyway, runs great, but on a recent long trip (3+ hours), about 1 hour from home, I notice the oil pressure gauge is reading low, and slowly going lower. I pull over and at idle it's bouncing around all over the place. It's never done this before, always reads as it's supposed to both at idle and above idle. So, while I figure it's the oil pressure sensor, I don't take a chance and have it towed to my indy mechanic. Tests reveal oil pressure good, so in goes a new sensor along with fresh synthetic oil.

Fast forward 1 week later, and on long drive again (8+ hours), and at about hour 6, I notice the oil pressure guage doing the same thing. This time I pull over, make sure oil is full, and then keep going. Obviously no issue, and once the car cooled off, hasn't happened since.

So, I'm sure my actual oil pressure is fine, but I can't understand why even with a new sensor, it's doing this funky gauge thing, but ONLY after extended periods driving. It really freaks me out to look down and see that gauge running at any thing less than "3" with throttle, so would love to get it fixed right. Any thoughts?

Thanks,

Gavin

You probably need a new lower engine wiring harness, about $80, or you could pull the old one and see if it looks repairable.

Oil pumps rarely fail----the problem of low oil pressure readings almost always turns out to be the sending unit (usually mounted very close to the oil filter) when oil pressure is truly a problem the tell tail sign will be a lot of lifter type ticking noises----that is a sign to shut off the engine as fast as possible

What oil are you using?

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2013 Fiat 500E.

The concept here is to read the thread and then respond. Type of oil wouldn't cause a bouncing eratic gauge. The sending unit has already been replaced.

If the oil is too full, the crank could be hitting the oil and foaming it up, causing air to be entrained, lowering oil pressure.

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Thank You!
Fred
2009 ML350
2004 SL600
2004 SL500
1996 SL600
2002 SLK32
2005 CLK320 cabrio
2003 ML350
1997 C280 Sport