My 95 E300D oil pressure gauge likes to read 3 all the time, even at hot idle. I know this is a symptom of a faulty sender, but I am not getting 3 bars with just the key on, it only goes up after the engine is running. When I turn the key but keep the engine off it doesn't change at all, does this still sound like a bad sender? If so, where is it on this engine? It's kinda crowded down below the filter housing, is it still in that same location?

BTW my idle is about 700rpm so it's not a high idle problem. Oil is 15w40 dino Lubro Moly, fresh oil as of yesterday.

Thanks a ton, this car is kind of new territory to me, I've been a die-hard 617 guy for years though.

IIRC it is in the vicinity of the oil filter housing. May have to look up at the housing area towards the back from underneath? Again, going from memory here. I've had to replace the sensor on the silver E300.

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Jim

Thanks I'll definitely have to give it a look. The puzzling part to me is the fact it remains pegged at hot idle, but doesn't exhibit the textbook sender failure symptom of being pegged when the key is on but engine not running. Is it possible my engine really does run that well? It has impeccable maintenance records from day one with Delo 400 changes 3k religiously, virtually zero blow by and very easy cold starts with plenty of pep through the RPM range. Even after driving two days on my new oil it remains nearly clear looking on the dipstick, whereas my 617 blackens it up almost instantly after a change.

IIRC I don't get any reading without the engine running either.

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Jim

Interesting, I had one kick off in my 617 a few years back and it would peg with the key on but engine off, perhaps the 606 is a little different in that respect. Either way, it's a cheap part and I think I'll replace it, it did appear to be working a few weeks back when I got the car, but even then it was pretty high at hot idle, just not 3 bars.

Thanks again

Mine won't show anything until started either.

It will read 3 bars until nice and hot, once hot 80-90C on the temp guage, it will fluctuate around 2 bars but go back to 3 bars around 1200rpm.

I'm running a 5W 40 full synthetic but when I run a Dino oil it does tend to stay around the 3 bars. In theory it shouldn't matter as the viscosity of the two are the same when hot but for some reason synthetics seem thinner.

What is the reading on your temp guage when warmed up?

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1995 E300 Diesel

That's interesting. Perhaps, in my wild-minded theory at least, your oil is not quite at its max operating temp and thus the viscosities are a little different between 5w40 and 15w40 even when up to temp, at least this time of year; but I don't know enough about chemical engineering and molecular sciences to really make an accurate guess.

When warmed up and cruising on the road the temp gauge reads perfect, just a hair above the 80c on the dash. It'll crack 85-87c pulling a really big hill in town, but it really runs at an ideal temp.

One thing to keep in mind is the infamous bio-degradable wiring harness of this era.

Do you know if yours has been replaced? It can give some false readings on the guages from time to time.

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1995 E300 Diesel

The harness is newer according to records from an independent Benz mechanic that did the work, so hopefully it's not that issue popping up again, or for the frist time if he just took the previous owner's money and did no work.

Have a look at the blue coolant temp sensor for the high speed aux fans. It's located on the top of the engine, closest to the front of the car. Your wiring insulation should look intact. If it's showing any copper of cracking in anyway then it won't have been replaced.

Picture attached of a bad wiring harness.

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1995 E300 Diesel

Overfill your oil by accident? An extra qt. can keep it pegged.

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1986 420SEL W/1990 560 SEL Full Power Interior Swap
1995 E300D
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Thanks I'll have to check that tomorrow in the daylight, hopefully it looks nice and fresh.

I checked and it is a few mm below the top red notch, so oil level is a-ok.

Maybe the sendor maybe not. The only way to tell easily is to change it. If something is questionable the sender is the most likely suspect.

Your mercedes is newer than a lot of members and the temperature gauge is operating well .There is no past mention of an instrument voltage regulator in the dash. Even if there was one it is not bad. Or the temperature would be reading abnormally as well.