OM642 3L Diesel Turbo Chatter / Surge and PCV leak.



Hi all - over the past couple of months I’ve taken this time to do a massive overhaul of my 2010 R300 CDI with the OM642.



It has hit 140k kms and i’ve had it for 90k kms of those. Up until recently, I didn’t notice any turbo surge/chatter when letting off the accelerator and it is really annoying me! I am also getting lots of blowby (as you can see in the video).



Firstly I have changed over my COMAND unit to a Kenwood double din and am waiting for the MOST amplifier converter so there is no music in the car currently. Maybe that is why I’m hearing all these sounds!



Re the overhaul, I’ve done, Lower ball joints, front airbag, front rotors/brake pads, transmission fluid, transfer case and both diffs and std engine oil and filter change.



Videos of the Turbo chatter / surge with intake on and off.



Intake on




Intake off




I originally thought the sound was drivetrain related (given the recent drivetrain work) but that was quickly dismissed as it happened in park/neutral. I then narrowed it down to turbo surge. I pulled the intake pipe from the front of the car and put my ear to it and it is definitely turbo surge.



Does anyone notice the surge in their cars (with the sound system off). It is prominent when lifting off at 1500 rpms plus revs (I guess when the turbo starts spooling). It is reverberating in the airbox and creating a grinding like sound but only sounds like that because of the reverberation in the intake system.



In the second clip you can see there is no grinding/whooshing sound with the air intake off.



Im thinking the surge has always been there but masked by the stereo, or it has recently started because of a Faulty turbo actuator - not opening fully/quickly when lifting off at low boost (see the video with the intake pipe off.



You can see the actuator moving much higher when the turbo is spooling at 2500 rpms to slow it down, compared to the small movement when revved to 1500rpm.



Im thinking if the exhaust side isn’t slowed, this will continue to create pressure in the intake valve which has no where to go except for out the intake system causing the noise.



I think the PCV issue is unrelated and is caused by putting too much oil in at the last change creating excess pressure which has blown the o-ring seals (new one was ordered a month ago but has been delayed due to Covid). Its also the first time ive used non MB spec oil (I put in 5-40 Penrite)… I wonder if that has contributed…



Does anyone notice this sound when lifting off after the turbo has spooled or have any ideas what could be causing the surge?



I know this is a common engine but I can’t locate this issue across any other make/model forums.