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  #1  
Old 09-04-2006, 09:55 AM
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low oil pressure

I just purchased a 1982 380sl. Oil pressure gauge reads zero. It moves a bit when engine is accelerated. I believe the pump may have failed. Has anyone changed a pump? Is there an engine manual available for the procedure? Is it simply the sending pressure unit? I noticed that there is a chain drive ? Is this chain the weak link? Any info would be appreciated to this new Benz owner.

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  #2  
Old 09-04-2006, 09:58 PM
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It is a bear to change the pump, because the oil pan is one piece the engine needs to come out to remove it. I pesonally have never heard of a pump or chain failing. I would try hooking up a gauge to verify the pressure loss before major surgery.

Good luck.
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Old 09-05-2006, 12:11 AM
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And what if the engine is worn out???
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Old 09-05-2006, 01:37 AM
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Not sure, but I think that this year still had a mechanical oil gauge, which might be leaking (it has a plastic tube from the engine) or is bad. You would be hearing some pretty bad noises from the engine by now, followed by nothing at all if the pressure was that low for any amount of time.
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Old 09-05-2006, 08:49 AM
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A quick check would be to pull the oil filler cap off and see if the oiler tubes are peeing on the cam lobes. If they are, then it is probably the gauge. If not, I would first look for a severely clogged filter or pick-up screen.

But Strife is right. At low oil pressure for very long, the cam gear would self-destruct very quickly.
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'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 09-18-2006, 12:15 PM
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Thumbs up low oil pressure

Thanks fo rall the replys. It seems the sender unit was NG, a mechanic replaced it but now the gauge is pegged at the top . It looks like he put in th ewrong unit, one for an idiot light. In any event , the oil is peeing on the cam lobes so there is pressure. Now I have to get the correct sending unit and change it.
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Old 09-18-2006, 02:30 PM
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Quote:
Originally Posted by ewenjo View Post
Thanks fo rall the replys. It seems the sender unit was NG, a mechanic replaced it but now the gauge is pegged at the top .
Actually, that is correct for these cars. It should move down from the top at idle, as oil pressure is reduced at low rpm.
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Old 09-19-2006, 04:50 AM
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Quote:
Originally Posted by ewenjo View Post
Thanks fo rall the replys. It seems the sender unit was NG, a mechanic replaced it but now the gauge is pegged at the top . It looks like he put in th ewrong unit, one for an idiot light. In any event , the oil is peeing on the cam lobes so there is pressure. Now I have to get the correct sending unit and change it.
Page62 is correct. The gauge itself is little more than an idiot light.
It should/will run pegged until the engine idles down. When oil does not pump in an engine that requires oil, inevitably, catastophic damage occurs,
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  #9  
Old 09-19-2006, 07:17 AM
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If there is a sending unit, then this is the electric gauge.

I had this problem on a 280SL. The way it seems to work is that 12v is supplied to one side of the gauge and the sending unit varies the resistance between the gauge and ground. The gauge is basically a voltmeter. Higher voltage, higher reading. If the wire to the sender is touching ground at any point, though, you get full voltage and the gauge pegs.

If you have a meter, hook it up to a 12V source and ground it at the sending unit and see what voltage you are getting with Key On. If you read 12v, you probably have a wiring problem as described above or a bad sender. If you see 0v, start the engine and watch what happens to the voltage. It should start out high and drop as the engine warms up. If it stays high, it is probably the sending unit. If it drops, but the gauge stays up, then you either have the wrong sender or the gauge istself is bad.

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'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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