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Discussion Starter #1
Have a 89 coupe that has 45 to 50 psi oil pressure when car is first started. After warm up the pressure drops to 8 to 11 psi. Could this be a sending unit or does the oil pump need replacing?
 

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Mine does the same thing.It's an 87' block.55-60 when first started then down to 8-12 at hot idle (7-800 RPM's
 

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Did you all check the oil? Mine does this when I run low on oil. After I get the oil level back to normal its fine.:thumbsup:
 

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I doubt it to be the oil pump as they really dont go bad. Maybe a bad seal somewhere?
 

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Discussion Starter #7
No leaks, no runs. motor runs good. using 10w30 royal purple. doesn't smoke or use oil. I think I'll replace the sending unit just for grins to see what happens.
 

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I take your car has high mileage.
below 17 at idle is pretty low.
When my c4 had 155000k miles my oil pressure was about 17-18 at idle with 5w30.
I then tried synthetic 15w50 and oil pressure never went below 22psi at idle. I ran synthetic oil from then on. The senders definitely do go bad though. Iv'e changed 3 in my C4. If it's an original one, Change it out for a newly calibrated one to be sure , or install a manual gauge to double check it.

You would be surprised...

:thumbsup:
 

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mine has 32K miles on it.I do believe it's the sending unit though.

I agree that an oil pump will not loose that much pressure from start up to running temperature. It does so naturally because of the Oil thinning slightly when hot.
T.D. Plese let me know how you make out with the new Sending Unit.
Cajun
 

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Before spending big $$ put in 5 qts of 15w-50 Mobil 1. This will hold pressure better than anything . . . all you have to lose is about 25 bucks this way and it may fix your problem: it did in my 86.
 

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Discussion Starter #11
oil pressure switch is about $30 bucks at auto****. Takes about 15 min to put in. Mobil 1 is 8 bucks a quart plus the filter. thats about $50 bucks. Royal Purple is $6 bucks a quart at a local dealer where I live. I'll change it this week end and let everyone know.
 

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You can add Lucas oil treatment to your regular oil, and it will boost oil pressure.
 

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Discussion Starter #13
Changed the oil pressure unit. Changed the oil and filter again. I now have about 28 psi at idle after warm up. I found the sending unit was original. I had read on other forums that the stock ones had problems and that if the unit was not black to replace it. My was silver not black. The unit cost 19.95 and was easy to install.

Now for the exhaust.
 

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Changed the oil pressure unit. Changed the oil and filter again. I now have about 28 psi at idle after warm up. I found the sending unit was original. I had read on other forums that the stock ones had problems and that if the unit was not black to replace it. My was silver not black. The unit cost 19.95 and was easy to install.

Now for the exhaust.

:thumbsup:
.
.
 
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