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-   -   1986 420SEL - low oil pressure (http://www.peachparts.com/shopforum/tech-help/248000-1986-420sel-low-oil-pressure.html)

simonshearer 03-19-2009 07:42 PM

1986 420SEL - low oil pressure
 
I have done countless searches on this subject to no avail. Would someone knowledgable about this subject please help me understand the possible causes of a gauge that doesn't change much from idle to full gas; about 1 on the 0-3 scale.

Is this a faulty oil pump, or possibly more than that?

Thanks.

Simon Shearer

04 Diesel 03-19-2009 08:17 PM

oil pressure
 
You might just need a new oil sending unit.

cliffmac 03-19-2009 09:03 PM

Maybe somebody put synthetic oil in the engine. The oil pressure sensor can't 'read' that right. I'd change the oil to mineral (as it should be) and see if the oil pressure gauge doesn't start working again, all of a sudden like......best of luck

04 Diesel 03-19-2009 09:08 PM

Quote:

Originally Posted by cliffmac (Post 2144763)
Maybe somebody put synthetic oil in the engine. The oil pressure sensor can't 'read' that right. I'd change the oil to mineral (as it should be) and see if the oil pressure gauge doesn't start working again, all of a sudden like......best of luck


I put synthetic in my 300E and it did not change the oil gauge.

simonshearer 03-20-2009 07:03 PM

I was assuming the oil pump needs to be replaced, no?

hanno 03-20-2009 08:02 PM

Don't assume the worst until you've eliminated all else. Disconnect the wire on the sender, test the gauge. If that's OK, then you change the sender (cheap compared to what an oil pump would be). I don't remember if its voltage or ground you use to test the gauge, but that's why service manuals and forums exist.

I have not experienced any strange behavior due to syn. oil. They're close enough that I don't think a mechanical sensor would care.

simonshearer 03-20-2009 10:08 PM

Quote:

Originally Posted by 04 Diesel (Post 2144714)
You might just need a new oil sending unit.

Would that be an "oil level sending unit;" or an "oil pressure sensor?"

cliffmac 03-20-2009 10:40 PM

at any rate, that's what I would do...change the oil and filter to good old Castrol GTX 10w-40 and Fram and see if that oil pressure gauge doesn't come back up. Heck, you should do those two things anyway along the way....

hanno 03-21-2009 08:44 AM

Since we are talking about the oil pressure gauge, it follows that the oil pressure sending unit would be involved. But oil level could indeed be a cause for concern. Back to the basics......have you checked the oil level, with the dipstick, as per the owner's manual (engine not running)? How long since the last oil/filter change?

simonshearer 03-21-2009 02:39 PM

Quote:

Originally Posted by hanno (Post 2146072)
Since we are talking about the oil pressure gauge, it follows that the oil pressure sending unit would be involved. But oil level could indeed be a cause for concern. Back to the basics......have you checked the oil level, with the dipstick, as per the owner's manual (engine not running)? How long since the last oil/filter change?

Today. Changed oil and filter. Castrol GTX 10w-40 as recommended. No change on the gauge. In fact it hardly moves off zero now.

Next step a new oil pressure sending unit.

Simon

simonshearer 03-28-2009 06:11 PM

that was it...!
 
I changed the oil pressure sending unit and now I have the gauge leaping to "3" immediately when given gas. :D

At idle it settles down to about "2" - is that right?

My 300D idles at about "1."

Thanks for everyone's help - especially for stopping me rushing off to purchase an oil pump!

Simon

hey_allen 03-29-2009 01:13 AM

On my 500SEC, idle runs around 1.5, 3 at cruise rpms.


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