Our 240D W123 had an oil cooler line go bad and lost 5 quarts or more.
Did not know of the problem until draining for an oil change. 2 1/2 quarts drained out.
Therefore a check of the main bearings is in order.
Any advice on how to proceed?

Have removed the oil cooler lines. Was able to find a factory replacement for the upper but not for the lower. The dealer no longer stocks the lines.
NAPA crimped a new high pressure hose on the old metal with steel clamps using a hand operated crimp tool made for a/c work. Looks solid but many people doubt that it will hold.

Any opinions will be greatly appreciated.

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My best advice:

Install the lines.
Fill the engine with oil.
Run the engine with special attention over the next 1000 miles for oil pressure, noise, and power.

At worst you waste some oil.
At best there is no damage.

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__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
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1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

Well--IF you really are determined to have a look at the bearings, its Normally nos.1 big-end that suffers first.--So this is the easiest to access after removing the bottom steel-pan and maybe the oil-pump for easier access....
--This is because its the 'last' in the oil-supply line and will be the first to lose pressure and suffer.

IF the nos 1 big-end is good, its a pretty good assumption that the rest will be fine.
--What is the oil-pressure At Idle--with a fully-hot engine?--This is another indicator of condition

As WHunter suggests though--is the easiest way--The outcome whichever you do will be the same....

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Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....

If you had 2.5 quarts in the pan I agree with Roy, don't fool around opening up the engine. It is not likely to have suffered any significant damage. I would not risk the investigation. Its much more likely you would cause damage investigating than any damage having occurred so far, IMHO.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Anyone ever retro fit a low oil warning system into these engines?

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Thank you all for your response.

What is your opinions on the oil hose?

Good question on the low oil warning system.

If the crimp ferrule and hose used is rated for oil at the temps and pressure needed it should be fine IMO. Looking at the red hose, the crimp is unusual in that it is lengthwise relative to the hose rather than circumference wise. Don't know if it matters but I would feel more comfortable if the ferrule is crimped like the black hose.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

If your Engine has a small separate Oil Pan I would drop that and look for Metal Fragments.
Next place to look is the Oil Filter and Housing.

He did not say what year 240D He had. It if has a Aluminum top cap on the Oil Filter Housing and there is room above to close the Hood He could do as I did in the below Thread.
But, as some pointed out if you are on the Freeway and you loose Oil Pressure the pressure has to drop a long way to trip the Low Oil Pressure Alarm at about 7 psi. That is not supposed to be enough to lube the Engine at high speeds. But, it is better than no warning at all.

Low oil pressure alarm for 617.952
Low oil pressure alarm for 617.952 - PeachParts Mercedes ShopForum

In a low Oil Pressure situation I think the Rod Bearings would go out first.

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84 300D, 82 Volvo 244Gl Diesel

There is not any evidence of metal shavings in the oil filter or housing or the oil pan.

I miss spoke calling it the main bearing. It is the rod bearings that I had intended to inspect.

What possible harm can be done by the inspection process?

Is their a simple low oil warning system? (Other than the dip stick)

The one I posted is the simplest. There is at least 3 long threads on the Low Oil Pressure Alarm.
Some of our other Members were working on something but I don't know if they ever finished it.

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84 300D, 82 Volvo 244Gl Diesel

I have seen ideas on this subject in the past but do not recall seeing a simple low level light.

Your device is a more accurate solution than the stock pressure gauge.
It should give a broader range of the actual pressure than the one on the dash that gives us 3 bars or about half of the actual oil pressure.
And it seems illogical for the stock gauge to show full pressure when there is in fact zero pressure.

I missed the Low Oil Level part.
I have seen none for the 617 or 616 Engines.

Some of the later Mercedes Diesels have the Low Oil Level indicator. However, that does not solve the issue either. If something happens and the Oil Pump does not work you Oil Pressure will stop but you will still be full of Oil.

From what I have read more Members have had loss of Oil Pressure from the Hoses leaking than from the Oil Pump not putting out pressure. So it is possible that a Low Oil Level Indicator would be a good idea if someone would come up with a way to retrofit one to the older Engines.

__________________
84 300D, 82 Volvo 244Gl Diesel

Did you know:
The piston rod bolts are single use fasteners, a new set is required every time they are loosened.


.

__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

Thank you Roy. You always have the last word. And I respect you and most of the time I take your advice. This time however I wanted to have a closer look at the #2 bearing, since the oil pan was off already, so I ask my wife to bump the starter to get #2 in the bottom position. She cranked once and I realized that the braided engine ground wire was removed (for the oil line removal) and we walked away. Five minuets later I returned to the car and found it smoking (FIRE). It seems that the engine was trying to find a ground through the Idle control cable and the insulation was melting and smoking even though the key was removed from the ignition switch. I disconnected the battery (something that I should have done first but I expected to only do an oil change in the beginning) opened the driver door and smoke came out of the passenger compartment from under the dash. Removed the instrument cluster and the panel under the dashboard and can see no damage other than the plastic idle control knob was melted and hanging at a 45 degree angle.

Lesson learned. Let Roy have the last word.