Could this be a bad sign -- (or good sign) ?
 

Picked up a 1982 W123 240D. From what I can tell, a rare survivor as it has no rust from what I can tell and having crawled all over it. I'm the 3rd owner and only 131K on the clock. Traced the titles back, owner to owner, as there was a copy of each prior title from the PO, e.g., first owner title, 2nd title in 2004. I have no reason to disbelieve the prior owner who said the car stayed in storage since 2004. Plus, all the rubber up front (suspension) appears new, or at least minty and it's MB parts. Other stuff not so minty.

Here's my question:

Oil pressure gauge immediately shoots up to 3 BAR when the engine is started (it pegs out on the gauge). HOWEVER, after driving it around for a while, it still stays at 3 BAR (pegged out). My prior MBs would hover slightly above 2 BAR after warming up.

Is this a good thing or bad thing for it to say at 3 BAR no matter what? Just find it odd

It's probably a gauge issue. You might want to try another gauge.

I had a 300D I bought that would immediately peg the red line on the temperature gauge when it was turned on from a cold start.

Dkr.

Is it fresh oil you put in or an unknown? I'm wondering if someone put some sort of molasses thick additive in there or maybe 20w-50 oil that doesn't really thin out at operating temp.

I wouldn't worry about it. It's during the winter and 616/617 do not run hot quickly. Real test would be in the middle of a very hot summer when operating for awhile.

With that said, you could pull your thermostat and pot test it to see if it's opening too early and not bringing your car to operating temperatures.


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The oil issue is both really, really old oil and brand new stuff. I think the "old" oil might have been years and years old and I re-did the pan gasket the following morning when I got home since I had a slight leak, and put in new with new filter. Just found it odd.

For what it is worth, I have an '82 240d and it does the same, will drop after warming to 2-2.5 on the gauge (at idle), then pegged again when driving.. currently using 15w-40. Runs fine..

I would not be concerned. Tight not high milage engine with idle perhaps at high normal. May just be normal. So basically probably a good sign.

You might open the oil fill cap and have a quick look to make sure lots of oil is up there though with the engine running.

Thanks Gents ... I guess I should clarify. It never goes below 3 BAR. Even driving around . When I shut the engine off, it obviously immediately drops, so I don't think it's the gauge, but I have a few spares I could pop in. It desperately needs a valve adjustment, however.

I say, they should always do this, as if they don't there is usually an issue. With mine, the issues where with the thrust piece....My euro never drops and the thrust piece was barely worn.....Though everyone else pitch forks me for saying at least on the non turbo's the gauge should peg....

I think everybody is misreading the question.

I think his issue is that at hot idle he is pegged (so at least he's at 3 bar, but no way of knowing by the gauge itself how much above that).

Normal situation in a W123 is:

1) Cold start and idle, gauge pegged
2) At anything above idle (hot or cold), gauge pegged
3) At hot idle the gauge should be between 2.5 and 1.5 or so. Minimum specified at hot idle is 0.5.

At hot idle with a gauge pegged (so you have at least 3 bar, and who knows how much more), I'd say you need to investigate a little further.

The oil gauge in your 240d is mechanical, which means behind the gauge cluster there's an actual oil line feeding into it. Did something get pinched there?

How old is the oil? What viscosity are you running?

It could also simply be that your engine is idling too high, as idling a bit above normal idling speed would peg the gauge at 3 as well.

Normal.

15W-40 in winter will probably never settle off the 3 bar reading. 5W-40 will come down to 2 bar.

My 617 would still return a 2 with dino Delo 15w40 after a long run on the highway even when temperatures in the NW were in the teens. My 606 will hover around 2.1 or 2.2 in winter with 15w40, slightly less with the synthetic Delo 5w40 it currently has in there, however.

Well, G is in Columbia SC... so fairly warm weather. It's been cool this week in Charlotte, if Columbia is the same and he's got OLD oil in the filter stem, and he used Dino oil for his change, and his engine is running cool... it'd be normal.
I doubt it's a gauge issue. Possibly an oil pressure line issue...
Maybe pull the gauge off and crank the motor over and flush out the line?

Ceristimo has it correct. What I am trying to say is that once the car starts, it stays at 3 BAR. Currently, nice clean oil, Shell 15-40 Diesel Engine Oil. I would say that the idle is probably around 50 or so too low .. vs. too high. I probably should adjust it a hair but I need to do maintenance first.

I have a somewhat new or I should say minty oil line which I installed at VSTECH's place about a year+ ago. I can harvest that line and install to see if that changes anything. Next thing I need to do is general maintenance, e.g., adjust valves, fuel system, et cet.

I don't think it's a problem. Seen it before, and it's usually attributable to the idle speed running a little high. Doesn't take much more than an extra 100 rpm for oil pressure to peg on a good 616.