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Hey guys, I'm doing some maintenance work and the breather hose turned to hard plastic over time with the heat and it cracked in a few places. I'm wondering if it'd make sense to replace this with an aftermarket material that'd be more durable and quicker than waiting 2 weeks for the dealer to get it from Germany. Any suggestions welcome, I was looking at a silicon heater hose with a high temp rating and a couple clamps.
Its not a very expensive part by any means its just a matter of convenience and not having to deal with it again for a good while. I found a URO parts kit online but I'm guessing it would be different for the v12 than a v8
Before you go any further:
If these breather hoses have become brittle, it is a clear sign of overheating.
The cause is the low-RPM breather circuit venturi inside the right valve cover, which is blocked due to oil coke deposits.
This situation will result in overheating of the oil cooler section that also handles crankcase ventilation.
If you don't fix this, your oil cooler will fail - a massive job to do.
there is an MB Service Bulletin on the breather venturi blocking due to coking.
If you fix the blocked venturi, just buy the replacement hose parts from MB, they are not expensive, and fit properly.
Done that, been there! Save yourself the oil cooler job!
Good luck!
Before you go any further:
If these breather hoses have become brittle, it is a clear sign of overheating.
The cause is the low-RPM breather circuit venturi inside the right valve cover, which is blocked due to oil coke deposits.
This situation will result in overheating of the oil cooler section that also handles crankcase ventilation.
If you don't fix this, your oil cooler will fail - a massive job to do.
there is an MB Service Bulletin on the breather venturi blocking due to coking.
If you fix the blocked venturi, just buy the replacement hose parts from MB, they are not expensive, and fit properly.
Done that, been there! Save yourself the oil cooler job!
Good luck!
that's extremely informative, really appreciate that. I'll search that thread right now. I just opened up the valve covers to change the gaskets actually. before putting the new gasket on I used a cleaner and scrubbed down the inside but they really weren't too bad at all but I'll see what that thread says.
I came across a series of videos a Mercedes tech did on you tube about changing the oil cooler, you're absolutely right. I think its a 30-40 hour job and definitely something I wouldn't tackle myself.
PMs are not neccessary; everybody has to benefit.
see attached; I can't find the complete paperwork right now, but search for the WIS.
You have to take the cover plate of the venturi housing, and then clean out all the coke, then reseal and install it.
Wow you weren't kidding about the coking...heres a picture if anyone is curious. There is a small plate held with 2 t20 screw and gently prying that open shows the build up
That buildup is scary did you clear it already ? From your pic it’s , not nearly the amount of gunk I’ve seen caked on American engines . I think you caught it early enough !
the one pictured in that workshop manuals link looks completely blocked. Hard to tell if yours was completely blocked too . This checking for the brittle breather hose should be a sticky thread for these early v12 cars
Well I cleaned it up pretty good. Almost makes me glad I snapped the hoses and got the heads up from Kraut to get this done while things were apart. I took a pic after I put the little cover plate on with some sealant but rest assured its 100% clean in there. I was careful in removing old gasket and cleaned the metal surfaces fully. Put some permatex ultra l grey and torqued it back on...I snapped 3 of the hoses and dealer gas 5o bring them in from Germany. I was looking for an alternate solution...high temp silicon house maybe soni wouldn't have to wait and maybe itd be a lit more durable but maybe the wait is worth it. Dealer said it takes about a week if it's in stock in germany
Well, he caught it "just in time".
On mine, there was a lot more coke, and no flow thru the venturi,
Of course, the MB Service Bulletin never made the connection to the failed oil cooler.
It is a rather strange form of positive crank case ventilation, and to my knowledge was changed with the introduction of the V12TT.
On that engine, the oil cooler has no components of the positive crank case ventilation, which could cause the failure due to overheating.
Yes - make it a sticky!
That buildup is scary did you clear it already ? From your pic it’s , not nearly the amount of gunk I’ve seen caked on American engines . I think you caught it early enough !
the one pictured in that workshop manuals link looks completely blocked. Hard to tell if yours was completely blocked too . This checking for the brittle breather hose should be a sticky thread for these early v12 cars
If you look closely, it is only about 1/8 at the venturi nozzle, and blocking that - even only partially - will do it!
It is the idle circuit; the open throttle circuit is separate, and not affected by coke.
So the broken pieces of the crankcase breather hose is on the way from Germany. so in the meantime I cleaned the intake manifold and the injectors. Its incredible how brittle those little hoses are. As careful as I was when I was removing them, they crack so easily once their time is come. I'm on hold until I figure out the ABC pump conversion so no hurry for the shipping.
Taking off the fuel rail takes a bit of care as well. The o-rings are snug and you want to pry it bit by bit and be able to lift the fuel rail straight up. After I cleaned it all I put the little clips that hold the injectors to the rail first and then put it as one piece back to the manifold. Gotta make sure everything is aligned well and take your time with it for sure.
According to MB the "shanked" manifold bolts should be replaced, as they are "stretched to yield" type.
(I did).
Good luck!
thanks for the heads up, I'll grab some when I go to pick up the hose pieces. MB said they won't be in till sept 4-5. Im trying the finish the PS pump conversion by that time and I finally managed to bolt up the new pump. The hydraulic line falls short 1/2" when I unbolt it from the bottom. Im thinking of a way to solve this without removing the like to modify. I'll try to find a hydraulic shop that can do a 15-20 cm line hopefully to connect it without unbolting it from the bottom
all done...I love the engineering of this motor. I replaced the breather hoses that were broken, cleaned the intake manifold, injectors, front cover plate, throttle body, gaskets replaced, new spark plugs and torqued everything back up. Replaced tandem pump with ps only pump as well and there is a very significant power gain.
Gentlemen, any of you have a pic of the Oil cooler hose lines, vaccum lines, that's connected to the oil cooler and the throttle body hose /vaccum lines. The vacum lines laying on top of the intake manifold. Just finished my oil cooler job but cant remember where the small hoses and vacuum lines go. HELP.
@kraut56 Are you able to remember the flow of the PCV hose that goes over the fuel line?
On your last picture it's right below the voltage transformer's wiring harnass
Also, I would like to invite you to participate in my new thread
It goes to a venturi inside the forwaed end od the rocker cover.
This venturi cokes up easilily, and when blocked will eventually cause overheat and failure of the oil cooler.
There is an MB service bulletin on this relating to smoke in exhaust.
Are you able to remove the venturi without removing the thermostat?
I already cleaned out the venturi, but I need to replace it as I've broken it last time I cleaned it.
Are you able to remove the venturi without removing the thermostat?
I already cleaned out the venturi, but I need to replace it as I've broken it last time I cleaned it.
Tim,
I have been stuck for a couple of days now wanting to clean out the venturi. I cannot locate anything on the M137 engine in front of me that directly matches the plate in everyone’s photos. Is the venturi located inside the passenger side valve cover? Is it the vertical plate in front of the engine that requires removal of the drive belt and pulleys to access? Is it the plate located around the thermostat that has multiple layers? I’m sure this is supposed to be obvious but I’m stuck. Thank you.
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