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Hi everyone, I'm new around here and hoping you outstanding folks can help with my issues...

I have an '87 U1700 Unimog, it was ex army and I suspect it spent many hours idling. Pretty sure the engine is an OM352A (turbo).

It smokes... a lot!. Thick white smoke for a significant time after start. It probably takes a warmup and then 5-10mins of hard driving for the smoke to subside, even then it doesn't fully disappear.

There is a slight blue tint, which I know is oil... but it doesn't appear to burn much.

My personal suspicions are stuck rings and poor compression, I need to check the crankcase blowby.. is there anything else to look at to help diagnose the issue?

Has anyone had a similar experience?

Thanks
 

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Put something up near the Exhaust Pipe outlet and then smell it. If it smells like Fuel then the whiteness is unburned Fuel.

Then I am guessing as the engine comes up to temp the Fuel is burning.

I am only familiar with older diesels that have glow plugs for use during start up. If they are not working there is smoke and sometimes rough running till the Combustion Chamber becomes sufficiently warm to burn the fuel.

If you think you have stuck Piston Rings you can remove Injectors or if it has them Glow Plugs and dump in something like Marvel Mystery Oil and let it soak in for a few weeks and rotate the Engine and repeat that.

My only experience is with the Marvel Mystery Oil. I had removed the Fuel Injection Pump from my Volvo Diesel and the Car sat for a year.

When I got it running it had hazy gray smoke all of the time.

The stuck piston rings was just a guess and I was skeptical as to if the MM Oil was going to work. I removed removed the Glow Plugs and dumped in about 1/4 cup per cylinder. It soaked a week and then I rotated the engine and re-did it but I only got to soak it 3 days more and I had to use the Car.

I cranked the engine to blow out any excess oil so there would be no hydrulic lock before installing the glow plugs.

I drove the Car around the Corner from my Back Yard to the front Drive way and changed the Oil and then took it for a drive on the Freeway. There was already some benefit but it took several days of driving for the smoke to clear up. So it worked for me.

I have read claims that full synthetic Oil will also free up sticking piston rings but it takes like 200-300 miles of driving.

In any event despite what is said on the Bottle don't dump anything into the crankcase Oil like MM Oil that would dilute it. Let people do that to the cheaper gasoline engines if they want to.

Also if you read articles on dumping stuff into the cylinders to free up Piston Rings people have dumped all manner of crap into their Engines.
Do that at your own peril.

The MM Oil was around before I was born and has no safety issues.
 

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If you can get at it you might remove the exhaust end pipes that bolt to the Trubo outlet and look inside. If the carbon is shiny oil is getting in there either from the Turbo Seal or the Engine.
It is normal for the carbon to be dry and a flat black color.
 
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