W164 smokes at idle

[beeza]

Hi folks I have an ML280CDI in the Dominican Republic. I'm a Brit expat living over here. The Merc dealers are few and far between so I prefer to do most of my own maintenance, as I don't trust most Dominican mechanics. I'm fairly handy at turning a spanner, but I think I need some advice from any experts that may lurk here......

The car smokes like hell at idle. It has always been a little smoky every since I've owned it which is coming up to nine months. These are the things I have tried so far:

A full service with genuine Merc parts, except the air filters which I upgraded to K&Ns.
Mobil 1 ESP oil, Merc fuel filter.
New PCV valve with sensor.
New MAF sensor for RH bank. (OBD2 fault code)
Installed a catch can mod to prevent oil entering the turbo inlet.
I had a little lateral play on the turbo shaft so I went ahead and replaced the turbo core for a reconditioned and balanced one.
The injectors have been removed and checked. No obvious worn nozzles.
Compression check is ok.

After putting it all back together and taking for a test drive it was smoking again. So I disconnected the tube from the turbo to the intercooler to find that it was full of oil. So it seems like the turbo is leaking oil, but it's a new one!

My question is: Would a blocked oil return line cause the oil feed pressure to be excessive and cause oil to leak past the bearings and into the turbo outlet? If so any suggestions on how to diagnose it or unblock it without major engine disassembly?

Thanks in advance.

 

[Ron . B.]

Full of oil ,as in flooded with oil? . If so the turbo ring seals are not working properly. The drain from the turbo should be easy enough tro loosen off and poke something through it to see if it is blocked,but it would be unlikely as there is a massive flow of oil through them.
Have you ever checked the oil level over a week of driving?
On the older diesels (OM 617) it's a simple check to loosen the oil filler cap while the engine is idling to check for crankcase pressure.
TRy it with yours..if it's looks like it's chuffing like puffing billy you may have a set of worn piston rings or other problems.

Another thing, how olsd is the air cleaner element? Diesels use Air to run,lots of it. If the air cleaner is blocked you lose a significant amount odf air resulting in clouds of diesel smoke . I don't know what the roads are like there but here in OZ it's something we have to do all the time because of the fine road dust.

 

[grober]

You may not have a blocked return pipe but rather an over pressurised crankcase. Evidently there may be a problem with high mileage OM642 engines where poor oil separation may lead to crankcase over pressure see post 133 here:-
Jeep OM642 CRD Performance Mod's - Page 9 - JeepForum.com

https://en.wikipedia.org/wiki/Mercedes-Benz_OM642

 

[beeza]

Thanks for the replies.

It looks like I have a worn engine! It's done 120,000kms. That should be nothing for a Benz! I'm not the original owner and I bought it with 90,000kms on the clock. I can only assume the original owner didn't keep up with the regular oil changes and use fully synthetic quality oil.

But yes, if you remove the oil filler cap with it running there is a lot of blow by pressure.

It seems crazy to condemn an engine due to the design flaw of inadequate crank case ventilation. But it seems that many are posting similar symptoms of the OM642 engine.

So what to do now? Live with it smoking until it eventually dies? Fix it ( A considerable job in a third world country) or flog it and buy a Toyota!

 

[grober]

From the jeep forum it would appear that one part-fix is to insert an inline auxilliary oil separation device. There are numerous makers of these and various ways of installing them e.g. re-routing scavenged oil back to the sump or simply to a catch reservoir [ which would have to be emptied periodically.]
This appeared to be a well engineered bit of kit.
http://www.parker.com/literature/Racor/Racor_Engine_Air_Filtration_-_CCV_Products_-_7790.pdf

A similar install is covered here and other posts on the jeep forum

Racor CCV Filter Installation - JeepForum.com