Is this Oil Pressure still within normal?
 

Hello to everyone!

As I was driving on a long stretch of open road yesterday, I noticed that as I cruised at about 90-100kph/56-61mph, the oil pressure gauge read just a tick below 45kpa(?). Despite the high engine note of the '76 200D 123 engine (I would estimate it to be at least 3600rpm), the oil pressure doesnt reach the max point of the gauge. Is this still within normal?

Before, I used to have the oil pres. gauge which had the 1, 2, and 3 Bar unit increments. But then it developed leaks so I replaced it with a US Version gauge with the 15, 30, and 45(kpa?:confused: ) reading. I was told that 0.5Bar Oil Pressure at idling is the lower normal limit for this engine (at abt 80-90C engine temp.). I do not know however, how to transmute Bar to Kpa. Nevertheless, I know that my engine AT IDLE operates well within the specs, but when its cruising at that speed, im not sure if the oil pres. is still within the specs. Just that, though these engines seem to be bulletproof, there are just those things which can really kill it... like inadequate oil pressure.

BTW, oil is not even 2 months old, engine rebuilt about a year ago more or less. When I drove, the ambient temperature was about 26C, engine temp normal at about 80C. The car has no overheating problems even with the AC on, which is almost always.

I apologize for the long post... just wanted to give details.

Thanks!

-Don A.

1 BAR= 14.5 PSI

I assume the "new" gage is reading in PSI (pounds per square inch).

Mine runs 3 BAR (43.5 PSI on your new gage) at cruise.

Thanks guys!

If it is indeed in psi (which it probably must be, just that i would have remembered if it was...no memory tonic available here):p , then that would mean its still pretty much normal given that it still above where the 2Bar line would be (above 30psi, that is). Do the newer benzes still have oil gauges? It would appear that this gauge is more helpful than a 'change oil' idiot light, doesn't it?:D

I was worried that another major repair, such as a rebuild, is cropping up again... hope that an oil pump change is far simpler and cheaper. BTW, how much is an oil pump?

In the meantime, ill just take it easy. The speed demon gets the better of me sometimes (as if THIS car's a speedster:D )!

Thanks again!

Oil pressure should be at 3 Bar~45 PSI at 1500 RPM and higher even when hot. If is is less, something is worn in the lubrication system. If the engine was rebuilt not long ago, I would suspect the oil pump if it was not replaced when the engine was overhauled.

What weight oil are you using? you might try a heavier weight oil such as 15W50.

P E H

Well... that something must be the oil pump! I vaguely remember the mechanic saying something about the oil pump when the engine was overhauled. Guess I thought that a quick fix of that part would be enough. Obviously it wasnt.

For the moment, I will continue to religiously follow the regular maintainance schedule in the hope that nothing will break (though obviously, the mechanical part that is broken wont get fix by this). As soon as the thing mentioned by TXBill happens, and hoping that I'll have the money by then, then I'll opt for a brand new oil pump.

As for the oil, I used 4liters of sae15w-30 Delo500 and about 2liters of sae40 monograde Delo500 at the last oil change. The monograde was used to reduce thinning of the oil at high operating temperatures. Back here, ambient temperatures rarely dip below 23C and is normally within the 30-35C range during daytime, which is why the oil must not be too thin.

-Don A.

One other thing...
 

I forgot to mention: when the engine starts cold, the oil pressure shoots up to the top of the gauge (45psi/3bar) even without revving the engine! Why is this? If in fact the oil pump is worn, then why is it that when the engine is cold, it seems to function quite perfectly? Is it simply because the oil is still relatively thicker which is why it exerts more pressure?

Or could it be, say, a wrong oil filter? But then its a perfect fit when I replaced it... weird.

-Don A.