Oil pressure issues

[Mario765]

Hello all,

my D24TIC (engine from 1994) has developed some oil-related problems. It just surpassed 520000km (about 320k miles) so I don't know if it has reached the end of it's lifespan or if there is still hope.
Anyways, the problem I'm running into is low oil pressure and high oil consumption.

The oil consumtion has always been higher and is now at about 1,2l/1000km (600 miles), which I think is acceptable in itself, however, the thing smokes like a freshly-lit campfire, even at moderate throttle and especially on cold startup. This is getting embarrassing in parking lots and at work.

And perhaps more worrying is the fact that now, whenever the engine is warm, the oil pressure light comes on at idle and slightly above idle. Depending on engine temperature, it sometimes flashes or stays lit.

You can also hear the valvetrain getting much louder as it used to be when the engine is warm. Certainly not your normal diesel nailing.

What do you guys think? Could the issue be solved with thicker oil? (I'm currently running 10W40 Motul oil) Or is the engine simply too worn? Also, could the turbocharger be the colperate for the blue smoke, or are the piston rings/valve seals more likely to be defective?

I thought I'd ask here before I take any further steps, too see If it may not be worth the effort.

Btw: The engine is always maintained and has brand new glowplugs, overhauled injectors, new timing belt last year and doesn't leak a drop of oil towards the outside.

Thanks and greetings from Germany,
Mario

[ngoma]

The apparent low oil pressure is most concerning. Try fitting a temporary (or permanent!) real oil pressure gauge to give you a better idea of the actual pressure under various conditions. The warning lamp sensor, circuitry, or wiring might be sending erroneous signals.

Oil pump wear is not unheard of, probably the most probable suspect.

Running higher viscosity oil is worth a try, but not a complete solution to the underlying problem. Maybe also try overfilling (1L?).

High oil consumption would have us take a look at the oil control rings first, then maybe valve seals or turbo. How bad is the blowby? Have you checked the compression? Has the engine been overheated (could permanently relax the piston rings)? Has the engine repeatedly been run under high load before reaching operating temperature?

The fact that there are no external leaks would make me want to save this one for sure!

[jpliddy]

hello my 940 has done 296000 miles now been in my ownership for near 23 years
it has been using 1 litre of oil between 5000 mile services since i owned the car
its not been driven too hard by me, but im interested in how long these engines will last before major engine work as the costs may be to high to pay for them as im limited capability on that side i can do a lot of basic maintenance myself,
i have run the car on millers XFE 10 40 semi synthetic oil for 21 years and now been advised to use a 5 40fully synthetic oil millers which i now do, the engine may sound a little bit more noisy when hot i just hope it will last me out but who knows , the car has been a great servant i , i have no problems so far with oil pressure but that may be in the future. there is some very good advice on this web site these people know these engines inside out let us know how you progress!

[Mario765]

Thanks for the replies.

You're right about the oil pressure gauge, I have one on hand and will install it as soon as possible. I will also do a compression test next.

I avoid high load when the engine is cold, but since my place of work ist right next to the Autobahn I have to give it a little more throttle than I'd like to get up to speed. I think the engine should normally be able to handle that, tough.

But since the compression will most likely be less than Ideal, what you are saying is that I'm basically looking at a complete overhaul or at least engine-out of the car work.

I know that will get expensive if done right, so I'm thinking about putting another engine in that I have (D24+T).

But before I do that I'm going to try your overfilling tip and thicker oil, certainly worth it before pulling the engine.

[ngoma]

Compression test is just to get a general indication on the condition of the piston rings, to help pinpoint the cause of the oil consumption. My thinking was if low compression, we can deduce the oil control rings are also weak.

If that 's the case, not sure a complete overhaul is necessary. Might get by with new rings, possible cylinder rehone. Requires oil pan removal so engine out of car makes it more accessible.

The high mileage might be a factor, especially if the engine was run for a significant time on non-synthetic oil.

Does the engine start easily, at all temperatures? Sometimes a clue to poor ring sealing is hard starting when just warm enough to not call for glowplugs yet not hot enough for better ring sealing.

Turbo oil leak could be another factor but I lack experience with this, maybe someone else can share?

What is the blowby (how much smoke puffs out when removing the oil filler cap)?

Originally Posted by Mario765

I avoid high load when the engine is cold, but since my place of work ist right next to the Autobahn I have to give it a little more throttle than I'd like to get up to speed. I think the engine should normally be able to handle that, tough.

Be careful with that. We had a trashed D24T from a person that lived at the bottom of a long steep hill. Approx. 130,000 miles, solid maintenance record from a good shop, etc. but the engine died an early life from all the hard mornings.

[Mario765]

The blowby is above normal in comparison to my 760. When you pull the dipstick oil even splashes out.

I know that driving a cold D24 straight on the highway is far from ideal, but what can you do. I shift as fast as possible and only accelarate to 80km/h so about 2000-2100rpm in overdrive.

It always starts, just a little rough when dead cold. Sounds like its missing on one cylinder for a minute or two.

But the compression test should tell us more. If it's low, for example on cyl. no. 6, which is my guess because of the higher thermal stress, I'm going to swap the engine and set this one aside to live another day.