Best oil for cleaning and stopping blow-by

OM605

OM605

Joined
Jan 3, 2020
Messages
1,002
Location
Brittany
Hi everyone, recently bought another MB diesel, a 97 W202 C250 Turbodiesel this time, with the OM605 turbocharged engine. It has 370k km (about 230k miles).

It has quite a bit of blow-by, the cap isn't really dancing but it looks and sounds like it would fill up a plastic bag in no time. I don't know much about how the car was serviced. All i can say is that even with an almost dead battery, it starts beautifuly at the first crank rotation when cold and it pulls quite hard for what it is. Maybe the provious owner ran it on crap fuel and not enough oil changes and mostly did short distances.

Perhaps the rings are coked and i could slowly improve things with a bit of TLC. What oil would you use? I'm not talking about specific brands as i live in europe but mostly specs. All PCMO are A3/B4 rated but i also have access to a good selection of HDEO as i have a tractor supply store nearby. Which HDEO specs should i look for?
 
Lubener said:
Don't expect miracles. No oil is going to renew worn parts or going to clean 26 years of neglect away.
Click to expand...
Sure, but from experience i've witnessed reduced blow-by on old MB diesels after a few years of short OCIs and lots of freeway driving. I think this car wasn't neglected or abused because it has very little issues other than the headliner. On the W202 the recommended OCI was 15k km, it looks clean under the oil cap but i think that's way too long for a diesel doing short trips.
 
  • Like
Reactions: wlk
Add or substitute 1 litre of motor oil with kerosene and run the engine for 6 minutes at idle, than Change the oil & filter.
 
OM605 said:
Sure, but from experience i've witnessed reduced blow-by on old MB diesels after a few years of short OCIs and lots of freeway driving. I think this car wasn't neglected or abused because it has very little issues other than the headliner. On the W202 the recommended OCI was 15k km, it looks clean under the oil cap but i think that's way too long for a diesel doing short trips.
Click to expand...
It it were bad enough, there would be crud present under the oil fill cap as well as in the valve covers. Doing a couple shortened oil change intervals is the most I would do without resorting to the heavy chemicals.
 
Not sure how this would work on a diesel unless there are glow plugs to remove... but I've significantly reduced blow-by in older higher mileage gasoline engines that had coked up rings.

I removed the spark plugs and sprayed a heavy amount of Berryman B-12 into the cylinders once a day while the car sat over the weekend. On the last day I added some MMO just to add some lubricity before startup. With the spark plugs still out I rotated the engine a few times just in case there was still oil/cleaner in the cylinder.

Before firing it up I changed the oil to get rid of the B12/MMO that made its way into the crankcase. Smoked alot... took it for a long drive on the highway with OD off to keep the RPM's up. Helped alot! Might take a few times.
 
Lubener said:
It it were bad enough, there would be crud present under the oil fill cap as well as in the valve covers. Doing a couple shortened oil change intervals is the most I would do without resorting to the heavy chemicals.
Click to expand...
The other thing is try to get the pcv valve / oil separator etc taken out and cleaned. Sometimes when oil has been overfilled this gets saturated with oil and you see blowby from the dipstick - without the usual symptoms of a worn engine such as knocking, excessive tailpipe smoke, reduced pickup etc.
 
How do you know it is the compression rings vs the oil control rings? Is it burning oil?

Maybe trying B12 Chemtool, an additive with harsh solvents, or straight up toluene in the combustion chamber might help reduce any oil consumption or even blow by?
 
SureshR said:
Did you try cleaning the oil separator?
Click to expand...
Not yet, i have to replace a bunch of gaskets and will try it at the same time.
Owen Lucas said:
How do you know it is the compression rings vs the oil control rings? Is it burning oil?

Maybe trying B12 Chemtool, an additive with harsh solvents, or straight up toluene in the combustion chamber might help reduce any oil consumption or even blow by?
Click to expand...
Blow-by should be caused by cylinder bores and compression rings not sealing properly if i'm not mistaken. The fact this engine doesn't burn oil but has blowby makes me think that liners and oil control rings are ok but compression rings might not be sealing as they should because of potential carbon build-up in the ring lands preventing them from moving freely. Like SureshR said, i have to remove and the CCV before drawing conclusions.
 
Does your engine have an EGR that you can block off or delete?
IMO, a little blow by on a 26 year old engine isn’t a big deal.
I’d run a 10W40 hdeo E6, in Canada, PC Duron.
 
@OM605, I don't have any profound wisdom for you, but just wanted to say that when I saw your avatar I thought "Huh? No spark plugs?" before the Aha! moment when I realized you owned a diesel.
 
OM605 said:
Not yet, i have to replace a bunch of gaskets and will try it at the same time.

Blow-by should be caused by cylinder bores and compression rings not sealing properly if i'm not mistaken. The fact this engine doesn't burn oil but has blowby makes me think that liners and oil control rings are ok but compression rings might not be sealing as they should because of potential carbon build-up in the ring lands preventing them from moving freely. Like SureshR said, i have to remove and the CCV before drawing conclusions.
Click to expand...
So the PCV siphons blowby vapor back into the intake manifold to avoid venting it. If it is clogged, there is blowby.

If you had worn bores or compression rings, there would be a bunch of other things wrong with your car such as low pickup, juddering, excessive exhaust fumes and such.

So, try to clean the PCV first and THEN look at opening up your engine if this doesn't sort the issue out.
 
michaelluscher said:
Is HPL engine cleaner recommended for diesel engines?
Click to expand...
I would gladly test that product but it's not available in europe.
userfriendly said:
Does your engine have an EGR that you can block off or delete?
IMO, a little blow by on a 26 year old engine isn’t a big deal.
I’d run a 10W40 hdeo E6, in Canada, PC Duron.
Click to expand...
First thing i did when i got the car was to remove and plug the vacuum line to the EGR. I can find that easily but why E6 specifically ?
kschachn said:
Have you performed a leak-down test on the engine? If so what are the results?
Click to expand...
Not yet, probably won't happen since i'm too lazy to do that. 😅
 
You must log in or register to reply here.

Similar threads

OM605
Oil for an old Mercedes manual tranny
Replies
16
Views
1K
OM605
Q
Spec sheets for Purolator One & Boss, Mobil 1, and Fram Ultra Synthetic oil filters that fit Honda/Acura, not sure how to interpret some specs
2
Replies
25
Views
1K
paulri
Superflan
OM605: importance of MB requirements? VS Rimula R4 L 15W40
Replies
15
Views
3K
Superflan
M
Oil for 2022 Kona N - LSPI or wear?
Replies
9
Views
2K
bhvrdr
mccandish
Another Toyota oil burner saved by a Berryman B-12 piston soak!
2
Replies
23
Views
5K
SubieRubyRoo
Back
Top