95 E320 oil pressure
 

Say it isn't so... I have been running Mobil 1 0w40 in the 95 E320 wagon for a year and a half with no problems. Now when warm, it is dropping below 1 bar oil pressure at idle when it is in gear (slightly less than 500 rpm on the tach). In park at idle (slightly above 500 rpm) it hovers around 1 bar. It used to stay around 2 bar at idle. The pressure does peg at 3 bar when driving.

I am at a loss as to what to check or do. There isn't any oil in the coolant or vice versa. Do the senders and/or gauges go bad? Do the oil pumps ever go bad? Would the bearing clearances open up seemingly overnight so it won't hold pressure at low rpm? Should I just change it to heavy dino oil and see what happens? I like this old wagon and would really like to keep it on the road.

Thanks for the help and advice.

Tim Benner
Dayton, Ohio

I'd start by changing oil and filter. Pressure sender could be going bad, would probably be my next swap, or check pressure mechanically.

Changed the oil & filter
 

Thanks for the idea!... Feeling a little more optomistic now. No change in the oil pressure after the oil change. I'll replace the sender and see what happens.

Tim

Your oil pressure is perfectly normal, ideal actually, no reason to do anything except stop worrying about it.

Seriously?
 

I thought that 2 bar at idle was OK and anything below 1 bar was big trouble. But why did it change? Maybe the new sender would be a good idea anyway just for the warm fuzzy feeling it provides.

Thanks,

Tim

Check your owner's manual. It's fine to be under 1 bar at idle.

OK Dayton Ohio. my brother lives in Kettering by the NCR course. The oil pressure gauge is not designed for synthetic (and I bet your owners manual doesn't call for synthetic). I had the same problem on my 300TE, the oil pressure gauge was not looking good. I went and had the oil changed to Castrol 20-40 and goddamn! pressure gauge went right back to where is should be, low and behold, the idiot who I bought the car from had put synthetic in it. Everything is fine now, I am convinced that the indicator gauge was confused because of the junk synthetic stuff. I am sure of this fact.....bet that's it...just go have the oil changed (all 7 quarts of it) back to mineral oil...bet the gauge comes back up....

Um. Or not. Use synthetic oil. MB recommends 0w40 Mobil 1 to be used in all MB motors. I use it in our 300E and it runs awesome with it.

Mineral oil? Yeah right....

Tim, seriously doubt that the synthetic oil vs. mineral oil has any effect on the oil pressure; however, the weight oil you are using may have some effect. Factory fill for that vintage engine was 15W40 mineral oil. I run Mobil 1 15W50 year round in our 1995 E320. You may want to run the heavier weight synthetic oil in the summer months, if not all year.

Where do you get this stuff? Mobil 1 is just one of many approved synthetic oils. And the requirement to use synthetic oil is only a product of the FSS lawsuit settlement, and applicable only to U.S., vehicles, and only post 1997 FSS vehicles at that, which does not include the subject of the thread. You're confusing what they want to sell with what is approved.

Thanks for all the info
 

I didn't mean to start any oil arguments. In the service record part of the manual the dealer (in Mississippi) was filling it with Kendall 20w50 so they apparently thought dino oil was OK. I have used the Mobil 1 0w40 for a year and a half, idling at 2 bar, with no indication of problems until now.

So something has changed. Either oil clearances have opened up - VERY bad. or the oil pump needs replacing - BAD or the sender unit needs replacing - Not so bad... hands stay clean. I have a sender on the way. and will let you know what happens when it is swapped .

Thanks again.

Tim

Tim, good idea to replace the oil pressure sending unit. At 145,000 miles it would be surprising if the oil pump needs replacing. Mineral oil was/is fine for that vintage MB engine. It's more a matter of routine oil changes to prolong engine life.

2 bar at idle would be the abnormality - 1 or less would be typical. But if a new part makes you feel good you should do it.

Tim, as Dean mentions your existing oil pressure sending unit seems to be working fine ... 1 bar at idle is normal. It may be best to leave well enough alone and install the new oil pressure sending unit when your gauge shows 0 bar at idle. Recognize that 1 bar is approximately 15psi.

it now shows 0 bar at idle
 

Last night I warmed it up, drove it a few miles and by the time i got back the gauge read 0 pegged at idle. Took off the filler cap and saw plenty of oil splashing the cams and a steady stream flowing down into the gallery. More oil splashed at 1000 rpm than at 500 rpm but the stream didn't change much.

I scoped out the sending unit to see how much time is was going to take and it looks awfully tight back there. This is best done from under the car right?

The attention to the oil pressure may have averted a potential disaster... see my post on fuel lines.

Thanks guys.

Tim