Worsening Oil Pressure - How much danger am I in?

[Andrew280SEL]

While not W116-specific (this is to do with my W123 230E), I imagine the principal is pretty much the same for any of the models of this vintage.

While the 230E has been going great and had great oil pressure when I first got it, very recently the oil pressure started to dip a bit even while revving more than idle speed. The first day it happened I noticed it didn't really want to stay on the top marker (3) in the 1000-2000 rpm range. Anything over that and it went up to maximum no problem.

I checked the oil, and much to my (pleasant) surprise despite the fact I have done just over 1000 kms in the car since I bought it, it hasn't actually used any oil. So it's certainly not a "low on oil" issue.

Then recently I had to drive somewhere and noticed it was dipping off the top marker even at highway cruising! I should also mention the problem is most noticeable with a warm engine. Cold, the pressure seems a bit better.

Now, while it's not due for a service yet technically (not for another 8000kms or so actually), I am sure it sat around a little bit before I bought it and I'm assuming (and hoping) it's just the oil filter clogging up and needing to be replaced.

See pics below for an idea of what it does on the highway presently.

Pic 1: http://i.imgur.com/gyvMS56.jpg
- Revs at approx 2600 RPM, light accelerator pressure and oil pressure clearly dipping off the maximum marker

Pic 2: http://i.imgur.com/NO6IDg3.jpg (sorry for blurry)
- Revs over 3000 RPM, under moderate acceleration, oil pressure at max

My question is, I clearly need to get the car to my Merc man, but how much danger am I in currently driving with that level of oil pressure? Is it too dangerous to the point where I should just bite the bullet and get an oil filter and do the oil change myself, and see if it helps?



EDIT: I like how the fuel gauge goes UP in the second photo despite it being taken a couple minutes after the first Typical old Merc fuel gauge

 

[BenzBoy]

Your first step is to have a technician hook up a master gauge to see if the problem lies within the sender unit or actual gauge - or if the problem is genuinely low oil pressure. Your filter has a by-pass valve so even if its clogged the oil should still maintain pressure.
Doing an oil and filter change won't hurt but it probably will have no impact on your problem readings.
Regards,
Brian

 

[Andrew280SEL]

I could be wrong and would have to confirm this, but I think the W123s have mechanical oil pressure gauges.

 

[BenzBoy]

I could be wrong and would have to confirm this, but I think the W123s have mechanical oil pressure gauges.

Andrew, I don't think you are wrong but it's still worth checking against a master gauge - what you are reporting in the way the pressure fluctuates is all a little strange and does need to be investigated.
Regards,
Brian

 

[sean sherry]

Yes, as with an Automatic Transmission the first stop is an Oil Pressure Gauge

 

[Andrew280SEL]

Alrighty, thanks Brian and Sean. I have somewhere to start now

 

[Helmet]

I'd be checking the oil filter ASAP. I've seen elcheapo filters cause this.

 

[Styria]

There could well be some concern regarding this potential problem. I drove a 6.3 the other day with similar symptoms, and when I suggested to the owner that he may (should) consider using a thicker oil and perhaps an additive, he told me "tried all that already - I think that the bearings are gone". His words.

On the ROVER V8 models, 45lbs./squ.in is the desirable norm, but they also have an oil pressure light that comes on at seven pounds per square inch. At one stage, I had a car that would regularly show the red light on idle, but it performed very well for at least two to three years showing those symptoms. Maybe Mercedes could be different, but I would not hit the panic button at this stage. Regards. Styria

 

[sean sherry]

From Helmets coal face .. words of experience
I found that lot of after market Oil Filters are rubbish.
Two things I have learned the hard way about Parts, are to use genuine Filters and genuine Brake pad. Or at least from the O.E. suppliers.

 

[Oversize]

If the filter blocks up the bipass will prevent oil starvation but the oil pressure should remain high. However if the filter has collapsed and is providing little resistance there may well be a drop in oil pressure. Definitely worth checking.

As a side note my AU V8 has developed a knock on warm startup but oil pressure is fine. It improves if I change the oil and filter. Not sure how much longer it will last but it does still perform well so the knock would have to be almost unbearable before I'd take action and get a new engine/car. I now use high mileage oil since it's done over 300K kms. I regard anything over 100K kms as 'high mileage' and use the factory spec oil as a guide only. Thicker oil is far better but apparently does rob the engine of some power.

Just saw a story on Sunrise about a Volvo hardtop that clocked 3M km on the original engine. A world record apparently but not sure if it's been rebuilt at some point

 

[aussie 6.9]

I had similar problems with a 240d Merc once and it turned out that the oil cooler was clogged and the oil was running too hot causing low oil pressure. Good luck

 

[Andrew280SEL]

Gee, I thought I'd have updated this weeks ago

Anyway, I did end up doing an oil and filter change. And what a difference! The 230 has max oil pressure even idling under load

The old filter had "Made in Germany" written on the top of it, but the brand I've not heard of before. I think it was Hengst or something.

Anyhow, the new filter in there now is a proper Bosch. I was surprised how small these filters are, I'm not surprised they can clog.