Oil Pressure gauge
 

I've had my '84 380SL for 2 years now and have had very few problems(knock on wood), but there is a problem that keeps nagging at my sense of well being.

When cold the oil pressure gauge pegs at the top like it's suppose to, but when it's warm (the car) the gauge rarely goes below between 2 and 3. Is this normal? I've had nothing but diesels so I don't know what it's suppose to do after warmup. The car has 125K on the clock but due to a timing chain break the PO had all of the valves and guides replaced.

Thanks!

It varies from one model to another, but what you are observing is quite normal.

When your oil pressure sensor goes bad, it will either peg to '3' all of the time (including when you just insert the key and turn it) or not function at all.

Diesel or gas doesn't matter. Normal for at a truly warm MB is between 1 and 2 atmospheres, so staying at 3 is not really normal assuming normal idle speed of around 650 on that car since it is not adjustable. If you are idling much higher, there is a problem in your air management system. Also what weight oil are you using?

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Peter

It's running at about 650rpm which I understand is normal...any guess as to what it might be? I use 5W30


BTW, since I've been told that I look like Winston Churchill I think that I'll decline the offer for the Nudist organisation!:eek:

The oil pressure should sit at three at start up as she warms up it can go down to .6 bar before you should be concerned the lighter the oil the lower the pressure most of the time (synthetics also tend to lower the pressure but only marginally). At park running and engine warm .6 to three is fine as long as it goes straight to 3 on acceleration. Hope this helps. 5w30 is a light oil i would use 10w 40 as a minimum unless you live in the very cold climates. Do not mean to get an oil discussion going. Personally I like mobil15w50 as it covers my area's temps very well. A oil sensor can give wierd readings so that is a good place to start if you are concerned. My 560 sits at 2 bar in idle warmed up.
m

I'll concur with Martin on his complete post. May be a funky gauge. I also would recommend heavier oil. I run 20-50 in all my gas and diesel rigs here in the S.F. bay area. It is amazing that your reading is 2 to 3 with oil that light. If you shift to heavier oil it will probably exacerbate the problem. Check your owner's manual (you know that little book in the glove compartment that is still in mint condition) :D to see what is recommended for your climate.

Peter

I just checked today it is 2.3 in P idle and 2 in D idle usin Mobil 1 15w50

Autozen

If you are a card carrying nudist, where do you carry the card?

:->

Tower

Warm engine in my SDL shows 3 bar at highway speeds and 1.8 bar at 630 RPM idle. This using 15w-40 Rotella (dino) oil. Oil changed every 3000 miles. Engine uses maybe 1/3 quart between oil changes and has used this amount since new. :)

Tower,

Once you check in you don't need your card or wallet, but if you want to buy dinner or a soda or something, you carry money in an amulet pouch on a leather thong around your neck. My daughter made a beautiful pouch for me as a gift. She is still not a nudist, but her boyfriend , Scott, is trying to convince her. When you go to a nudist resort you don't find just beautiful bodies. You find people as they are. Some people are 75, some people are 14, some people are 10, some people have had a breast removed, some people have had a tripple bypass, some people are pregnant, some people are having a period, some people have a microscopic penis, some have beautiful bodies. The point is that nudists accept people as they are. I'm not coming down hard on you, man. I know you are funnin with me. So relax and check it out. I'm tellin you it is the most fun you can have with your clothes off. Don't worry, if you ask a lady for a slow dance, you won't get a boner.

Peter

I have a 1992 300SEL (W140). The oil guage works funny too. It fluctuates a lot during idle eventhough the engine's rpm is very stable. At idle, the rpm stays just a little above 500. Could this be linked to a bad oil sensor or a bad guage? I will be taking it in for repair. Someone stole my badge on the hood and the engine won't start without manually applying the throttle pedal. But once it starts it is very smooth except for the oil pressure guage.

Lok

Lok,

More than likely it is the sending unit. MB oil pressure gauges used to be bullet proof, but the quality went down in the mechanical guages to where the unit in just about every 123 chassis leaked oil. Now the electrical units are becoming par with the junk made for Detroit Iron.

Peter