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  #1  
Old 03-19-2003, 05:56 PM
Tim the 2Lman
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Question Oil pressure problems '93 300E

Guys thanks for your help in the past. This is a great forum.

I'm doing some work on a friend of mine's '93 300E. He gave me a small laundry list of things to fix. One of them is the oil pressure indication.

Problem: When started cold and until engine is hot, oil indicates above 3 bar on the gauge at idle. After the engine is up to operating temp, the oil pressure drops off to nothing, 0 , nada at idle. Accelerate the engine and it will resume above 3 bar until it idles back down and then it drops to nothing again. I suspect oil sending unit, but at $65 for the part, I really didn't want to shotgun it. I've purchased an aftermarket oil gauge to hook up temporarily, but from the top it is an impossiblity.

Does it sound like I'm on the right trail?

I would appreciate your input.

Tim
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  #2  
Old 03-19-2003, 06:33 PM
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Join Date: Apr 2000
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Why not remove the filler cap and see if the cams are getting oil at 0 pressure? If yes, then bad sender, if not, probably bottom end problems.
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  #3  
Old 03-19-2003, 06:36 PM
Tim the 2Lman
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Will do...

I can do that this evening. But, wouldn't I hear some knocking if it was truely not pumping any oil. It sounds the same regardless...very quiet. I can accelerate hard from an idle and hear nothing unusual.

Tim
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  #4  
Old 03-19-2003, 06:40 PM
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Location: Ontario, Canada
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What weight of oil are you running?
Maybe too light for the temperature? Just asking.
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  #5  
Old 03-19-2003, 06:43 PM
Tim the 2Lman
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Not sure

I don't know. I'll try to check his records and see what I can find out. It was just recently changed and he hasn't had the car very long, just a few weeks. The owner is out of the country so it may not be possible to find this out easily. What should it have in it?

Tim
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  #6  
Old 03-19-2003, 07:33 PM
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According to the latest Mercedes " News Flash ", Mobil 1, 15W50.
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  #7  
Old 03-21-2003, 10:50 AM
Tim the 2Lman
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Sending unit question???

Does anyone know what the resistance range or current flow should be on the oil sending unit? I'm getting about 2-5 ohms of resistance at idle and about 155 ohms at above 3K rpms. Interestingly enough is the fact that the resistance goes up about 10 ohms when the engine is turned off.

Does anyone know for sure???

tim
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  #8  
Old 03-21-2003, 03:02 PM
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Join Date: Feb 2003
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Doesn't the car have hydraulic lash adjusters?. My 1993 300E with the 3.0 liter engine does, and if the oil pressure was that low, I would think you would indeed here a lot of rattling coming from the valves.......
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  #9  
Old 03-21-2003, 03:55 PM
Tim the 2Lman
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That's my assumption. I can 'wrap it out' from an idle with the gauge showing 0 and hear not a tap a knock or a ping. Rev's nice and quiet and even. I just want to make as sure as I can about it before I buy the part considering if it doesn't fix the problem I'm likely out the $70.
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  #10  
Old 03-21-2003, 05:51 PM
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Location: St. Albert, Alberta, Canada
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There is a group of M103 owners having this very problem on the forum. Keep us posted. My Dad has "our" 1990 190E 2.6 back, and it's been doing that for some time. Since the engine runs normally, doesn't use any additional oil, makes no valvetrain noise at hot idle, and sends oil to the top end at hot idle with the gauge reading zero pressure, I dismissed it.

OTOH, I thought maybe the pump is going south, so I told Pop to keep an eye on it.
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