Suspicious oil pressure?

[Alan67]

Hi, I know it's not a lot to go on, but does anybody think that the oil pressure on this car looks a bit suspect?

The car is a 1992 SL500 with under 100,000mls.

 

[merc85]

yep should be 3 i believe at idle may drop a little once warmed but go straight to 3 wen the accelerator pedol is depressed

 

[John Jones Jr]

Yep. But I'm not au fait with the V8's but could be something as simple as faulty oil pressure sender unit or just needs a new oil filter (and oil change).

 

[bing]

At that temp ,100+c it will drop to 1-1.5 bar but should peg at 3 when you Rev it. However , if you have no record of the oil pressure switch being replaced in the past I would install a new one . Not a big job and it's right under the oil filter housing .

 

[BTB 500]

The coolant temp does look a bit high ... my 500 doesn't reach that even in traffic on a hot day. On mine the oil pressure at idle when the engine is hot is around 2 bar, it only has 54k miles though which may be another factor.

As mentioned the main thing is that it hits 3 bar immediately when the revs are increased.

 

[bing]

I would expect the auxiliary fans to be running at that temp. But that said, ambient temp only showing 22c which is not that hot, unless the temp sensor is faulty and maybe you're on out in the desert. I would look at the Visco fan operation if engaging as should.

 

[Alan67]

Hi again, well, I decided to buy the SL500. Driving home, I covered over 300 miles, and it never missed a beat. Amazing acceleration. The oil pressure rose to 2.75 ish as soon as the revs started to rise, and the temp guage sat pretty much where it is in the pic all the way home. Did notice the electric fans were on when I pulled in for fuel, but they switched off after about 30 seconds or so. Really nice car, totally love it!

 

[bing]

Congratulations! Don't mean to alarm you but what you're describing is not normal. As said , oil pressure should be at 3bar when you're on the move and , as with all MBs , normal operating temp should be at 85-90 ,not 105c ! Visco fan is suspect and it's a common failure . Does it really stay at 105 even on motorway runs and how low does it drop when fans are on ?

 

[w124nut]

Although not a V8, I had problems with my W124 E320 oil pressure. It read "3" when driving along but at idle, it dropped to "1" and sometimes lower!

My indy went through the process of fault finding replacing the oil and oil filter, then later the sender but with no real improvement to the read out.

Finally we suspected the oil pump and this is what was found:



The oil pump showing the impellers, note the scoring




There were metal shavings in the sump from the pump. Luckily, inspection found no damage to the engine itself. The strainer was clear of debris.


The following photo shows the oil pressure needle after a new oil pump was fitted and at the end of an 80 mile run.



If your oil pressure is still low and all alternative possibilities have not come to fruition, seriously think about the oil pump being u/s.

 

[John Jones Jr]

As per M-B: At operating temperature the oil pressure at idle may decrease to 0.3bar gauge pressure. When the engine is accelerated, the oil pressure should increase again immediately and reach a pressure of min. 3 bar gauge pressure at an engine speed of 3000 rpm

Now, from what I recall the actual max engine operating pressure is well above 3 bar (possibly 5 bar?), just the gauge only reads to 3 bar. 2.75 bar is simply too low.