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Old 01-29-2003, 05:26 PM
Registered User
Join Date: Jan 2003
Posts: 9
Oil pressure gauge stays at 3bar

I think its my oil sending unit on my 89 300CE, but want to make sure before changing it.

When first start the car, it would take about 3-5 seconds before it get to 3 bar. During driving it would stays at 3 bar, but when I come to a stop, it still at 3 bar. Should it drop from 1-2 bar at a lower rpm and resume to 3 bar at a higer rpm? Am I on the right track or its something else that went wrong. Thanks.
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Old 01-29-2003, 05:46 PM
94 E320
Join Date: Jun 2001
Location: Fairfax, VA
Posts: 437
onmy 94 e320 here is how it goes

at start up....3
during idle it drops from 3 to 1.5 or so
when i step on the gas it quickly shoots back up to 3

as long as its running or when i'm driving it remains @ 3
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Old 01-29-2003, 05:49 PM
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Join Date: Jan 2003
Posts: 9
Mine doesn't drop to 1 or 1.5. It just stays at 3 even at idle. Is this a problem?
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Old 01-29-2003, 05:53 PM
Posts: n/a
Have had same experiences with my old '80 240D and now my '89 300CE. "Normal" operating condition (on those cars) is for the guage to come up to max after startup and stay there while driving (moving). At a red light or other stop, it will drop down between the "1" and "2" mark, then max out again upon acceleration. I've noticed that when I put the shift into neutral, while at a stop sign, the economy meter drops to a lower level (indicating less fuel usage), and the oil pressure guage goes up slightly.

Just a guess, maybe not a good one, do you have too much oil in the engine? Too much oil will increase the pressure, resulting in damage eventually.
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Old 01-29-2003, 06:45 PM
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Join Date: Nov 2002
Posts: 63
My 95 e320 always stays at 3 bar when the engine is running.
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Old 01-29-2003, 06:52 PM
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Join Date: Jan 2003
Posts: 9
This question is for Volosong or anyone that can relate to this problem.

It seems to me that you own a 300CE as well.

Last week I've posted a problem about the seat belt retractor.
Mine got stuck on the passinger side. It doesn't move whether the door is closed or open. Did you ever have the same issue with you car. Thanks in advance.
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Old 01-29-2003, 06:57 PM
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Join Date: Jan 2003
Posts: 9
Yes, it is at 3 bar when engine running, but it should drop when shift to "D" drive at about 900 rpm.
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Old 01-29-2003, 07:36 PM
Posts: n/a
Oil pressure

Hi guys, hope the following puts some minds at rest. I am on my 5th Merc. Now and all have indicated oil pressure as you have described, maximum whilst on the move and coming down to 1.5 to 2.5 when at idle in drive, this is normal for these carís so no worries. After you have had the car for a good while you will be able to judge when you need an oil change by watching the oil gauge, I have always found that ( given fairly constant running temperatures ) that as soon as you notice the oil pressure dropping consistently lower than is usually the norm for your car at idle in drive, itís time to change the oil, try it, I found that this more or less coincided with normal oil change periods taking into account the oil used and driving patterns. Yes the oil pressure will rise a little if you change to neutral due to the slight increase in RPM and with no load on the engine from the transmission it will also use a little less gas.

PS I am still having all sorts of fun trying to cure a few ticking noises from the valve gear, anyone out there currently having the same fun let me know.

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Old 01-29-2003, 08:49 PM
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Join Date: Jul 2002
Location: Dallas
Posts: 330
My oil pressure stays at an indicated 3 bar all the time while the engine is running. Should drop down at idle. I hear the sending unit on these cars is a very common problem, so I haven't replaced it yet. I'm more concerned with no oil pressure. So yes, Philnguyen, you are on the right track.
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Old 01-29-2003, 09:29 PM
Super Moderator
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
I would be concerned that the engine is not getting to operating temperature. If it is - like the guage shows 80C or so and the heater works well, I would find something else to worry about.
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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Old 01-29-2003, 11:18 PM
Senior Member
Join Date: Dec 2002
Location: Visalia, CA
Posts: 379
For what it's worth, I'm a tech and see nothing but merc. and bmw, many merc. have oil pressure readings like this. If you've changed the oil and filter and seem to have no other oil pressure problems I wouldn't worry much. We've yet to have a customer complain about pressure to high, so we rarely look into it. Does the needle move/twitch at all, esp. when shifting into or out of gear? idle up/down? Hope this helps.
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Old 01-30-2003, 11:25 AM
Posts: n/a
Re: 300CE seat belt extender/retractor


I've only had my 300CE for about a month. It is a low mileage "cream puff" that was well taken care of by its original owner. The seatbelt extenders work as designed. Perhaps do a search in the archives. There might be something there. Sorry I cannot be of more help.

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Old 01-30-2003, 06:35 PM
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Join Date: Oct 2002
Posts: 75
Thumbs up sounds stupid I know


I noticed the same thing on the oil guage, when I went to take delivery of my 420 from my nephew. Not being a DIY'er he always had others service his MB. The neadle was at 3 bars, always and at stop, didn't matter. I thought to myself there should be some drop in it at stop in gear at idle. Still 3 bars, you guessed it, a quart to much oil, which I drained out the next day, before putting it on the road home. Now it drops to 2 bars at idle in gear, and the oil level likes to stay midway of the min and max lines on the stick. Make sure your not overfull.

1989 420SEL 105575 miles
Pearl Black/Grey

1990 Chevrolet E-Cab C-1500
293,000 miles

1989 Olds Toranado Trofeo'
132,000 miles
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