Hi! I have a couple of questions about oil pressure. On my 1990 300 te the pressure when the engine is hot will be around 1 in N, and go slightly under 1 in D when standing still. It pops up to 3 at around 1500 rpm. This is all with AC off, turning it on will take away some more...

On a cold start it goes to 3, but it takes some seconds to go up when I start the engine.

Iīve always heard that itīs really bad to be under 1 no matter what, but my engine seems fit and good.

Is this normal and no need to worry?

Thanks! jm

Usually a value over 0.5 should be enough at idle, if it raises to 3 when pushing the throttle...

In normal conditions it should be 1.2-1.5 at idle and 3 when driving(in both cases, when engine has been warmed up).

~Nautilus

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1990 260E Sportline (that's 300E 2.6 for our American friends) -> sold
2001 E320 4Matic Elegance -> my Dad's daily drive
2005 Seat Leon FR 1.8T

I've read that the important thing is how fast it pegs out when the engine is rev'd above 1200 RPM.

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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.

Your oil pressure is OK.
Just keep up with regular oil and filter changes to keep it sweet.

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NormanB
230 TE (W124) 1989 with 153,000 miles on the clock - hoping for at least another 100K

...but your oil pressure sensor may be starting to deteriorate...

...wouldn't worry about replacement until it fails completely.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

In general I would say no. Chase it down and fix the problem as low oil pressure will lead to engine failure -- don't ask me how I know!

All I can say is that my Benz the oil pressure never went below 1.5 on a hot day with AC. If yours is less than 1 then something is wrong. It may be that your oil pump is failing. Replace it now before you replace the whole engine or junk the car. I would also tend to guess its not the guage either.

Just words to the wise. Also, in your case, was the oil pressure higher in the past? Has it been dropping over time? That should tell you that something is wrong also...

Good luck with it!

-=>Raja.

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1983 MB 190E, bought from Germany and shipped to the US in 1986.

I have same 103 engine in my '91. The pressure behaves exactly as you described, and has for the last 13 years.
First time I remember it going to less than "1" was the first hot day, when the car was one year old with less than 10k miles.
I use 10w-40. Thicker oil might raise it a bit when hot.
"1" corresponds to 15psi, so it's probably dropping to about 10-12 psi at slow idle in gear. The small-block Chevy experts say 4psi is sufficient at idle, with approximately 10 psi for every 1k rpm being a good rule of thumb to protect a Nascar engine.

So, fuggitabout it.

Thanks rbort and everyone else!

The thing is that when I bought this car the pressure was seriously messed up, it wouldnīt go over 2 whatsoever with a warm engine, idling at levels I wonīt say out loud...

So I bought it knowing there might be something funny with it, and had repairs in mind on the whole deal. So I immediately changed the oil and filter and it went ok at once, or at least as ok as it is now. And itīs gone about 6k km (4k miles?) in a couple of months, being stable.

Anything to check before changing the oil pump, as this is an expensive thing to change from what Iīve heard.

Again, thanks everyone! This forum is great for computer heads like me who love driving these cars, but have limited car mechanic skills.

Not the same engine but the same low oil pressure problem. I was running 15w-40w. I replaced the oil pres. sending unit and switched to 20w- 50w. Now it is at 1.3 in dr. when hot.

Another thing, I saw today after some hours on the road that the oil pressure meter was shivering when idling. Someone once told me that was a bad sign...

Is this a symptom of anything bad?

Hi

If you have not got the kit and have a concern that is niggling you , my recommendation would be to find a good independent specialist who can put a test gauge on the system to verify the truth and determine what is happening in the engine as opposed to what the instruments are telling you.

The developed oil pressure while obviously originating from the pump is the product the pumps output minus the losses which comprise the sum of design and wear losses - so if you were down on pressure (for real) a simple (but expensive) pump replacement may not cure the problem.

Good Luck.

PS:

Design losses = pressure drop across filter, leakage from bearings

Wear losses = excessive leakage from worn bearings , defective lubricating rails (end caps missing), oil pump reflief valve not seating correctly.

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NormanB
230 TE (W124) 1989 with 153,000 miles on the clock - hoping for at least another 100K

with my 87 420 well i'm probably the antichrist when it comes to oil and gas choices. i run regular gasoline 87 oct and not one problem or ping have i had in 18 mos of hard driving. i run castrol hi mileage 20w-50 for my oil [yes year round....but i change oil every 2500 to 3k miles with filter change]. with the engine at 80+c warm i have 1.5 bar at 500 rpm at 700 i have a solid 2 bar and the moment you bring the rpm up i got 3.

the car has the same tune on it when i got it off ebay at 3700$ arrived with 128k now has 160k. that's 32k just for commuting to work.

one point about oil pressure. pressure is fine & it is one indicator of oiling properly. the other point is oil volume. the 2 issues are not necessarily an indicator for each other. you can have decent pressure being reported but not necessarily the volume needed. this is where you've heard about only having 10 psi on hi perf motors at idle being ok. the reason is they have enough volume to sufficently oil the engine.

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Thanks Much!
Craig

1972 350sl Red/Blk 117k
1988 420sel charcoal/Blk 140k
1987 420sel gold/tan 128k
See My Cars at:http://mysite.verizon.net/res0aytj/index.html

Pound it to fit then Paint it to match!

There is only First Place and Varying degrees of last!

Old age and deceit will overcome Youth and Enthusiasm every time!

Putting the square peg in the round hole is not hard... IF you do it fast enough!

Old enough to know better but stupid enough to do it anyway!

JM,
Check out what your owner's manual says. I don't have mine handy but I bet yours says the same as mine, namely that as long as the pressure at idle is at least 0.3 bar, and rises promptly on acceleration, no problem.

Mine has ALWAYS gone down to about 0.5 bar in summer, with AC on, in traffic. Changing to Mobil-1 15W-50 keeps it above 1 bar at idle. That's not why I use synthetic, but if this worries you, you might kill 2+ birds with one stone by switching over.

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Steve
'93 400E

Strange things happen of late with oil pressure on my car (M103 2.6 engine)

Stage I: in the last 2 months it tended to show lower oil than normal on the dipstick(like it was burning it), but next morning the level on the dipstick was normal again

Stage II: it burned oil. Not very much, but still enough to be concerned. (Side note: oil was 15W40, mineral).

Stage III: completed with oil, plus an additive. Now it doesn't burn it anymore, but, when starting the cold engine, pressure gauge shows zero, then(after 4-5 seconds of idling, or after a push on the throttle) it jumps to the normal value of 3 bar. In traffic, pressure is 3 bar, at warm idle is even higher than before (slightly below 2 bar, previous was around 1.5 bar).

Are those 4-5 seconds dangerous for bearings? Should I flush the oil as soon as possible, and replace? Or can it be a faulty gauge?

~Thank you,

Nautilus

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1990 260E Sportline (that's 300E 2.6 for our American friends) -> sold
2001 E320 4Matic Elegance -> my Dad's daily drive
2005 Seat Leon FR 1.8T

I would say that it is taking too long to bring up the oil pressure.

I have the m116 engine (420 SEL), when the outside temp is above 32F, it jumps to 3 bars on starting. If engine temp is 80c, oil shows about 1.3 bars at idle. Engine temp. 100 or above, oil shows 1 bar.

Originally when I bought the car, oil would dip to .5 bar on a hot idle, but upon acceleration would come to 3 bar immediately. Here is what I did to get the oil pressure up.

1. Oil pan was dented. While replacing oil pan, I saw bottom of oil pump tower was actually broken. The rubber was rock hard. I replaced the rubber oil pump bottom sucker. Replaced oil pan, and gasket.

2. Popped the valve covers. Removed each and every HLC. All of them had thick black goop in the bottom. I pressed down on some of the them, and black tar like substance came out, which also felt gritty, like sand. Replaced all HLCs. Also there is a tiny hole about 1/8" in diameter on the rim of each HLC socket. It too was filled with black oil. I stuck a thin plastic tube into the duralube aersol can and flushed out those tiny holes. I could see the duralube foaming clear up through the adjacent holes. Replaced HLCs, rockers, checked basic position, replaced valve covers.

3. Changed oil to 5W50 synthetic, new filter, and now great oil pressure!!

In the winter, when the outside temp. -20c or lower, it does take 2 sec. to come up to 3 bars.

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1989 420 SEL