400E without negative crankcase pressure

[alpineviking]

I have a 93 400E that sends a small amount of crankcase fumes into the distributors. It has153,000 miles on it, and runs perfectly. A manometer shows zero pressure reading at idle, and climbs to a half inch of water column at 1800 RPMs. Could someone tell me if the vapor cannister and its valves are supposed to maintain a negative pressure at an idle? Thanks

 

[TerryA]

If your really smelling it in the distributors, I would change the oil seals behind the rotors and shields in the distributors.

 

[gsxr]

Not sure what "vapor canister and valves" you are referring to?

Pull the distributor caps, rotors, rotor bracket, and insulator. If there's any sign of oil leaking from the cam seals, replace them. You may also want to replace the insulators. Also, it's very common for the intake cam solenoids to leak oil which runs down the 45° angle to the bottom of the distributor cap, which can also cause issues.

Read the thread below for more details, adding the ventilation slots to caps is highly recommended *after* you fix any oil leaks:

FYI - Essential M119 Ignition "Tune Up" mods [Distributor cap vent / slot] | M119 Engine

Hi all, I have been meaning to address this on my little used 500E for years.... it is a problem I myself recognised about 5 years ago when I first looked at an m119 distributer cap..... Compare to any other distributor cap of the era such as an m104 and you will see there are NO ventilation...

www.500eboard.co

 

[alpineviking]

Thanks for your response. I did replace the oil seals behind the rotors and have replaced the distributor caps, rotors, and dust shields. I have cut additional slots in the caps. The contamination is reduced, but I still have concerns about lack of negative pressure in the crankcase at idle. It can bring about oil contamination. I wish that I could find out how the evaporation cannister functions at idle. Thanks again for your response

 

[gsxr]

The PCV system may be designed like this. I don't think the FSM has any specifics. The evaporation canister is for fuel system vapors, which are ingested into the intake system along with crankcase vapors, when the purge valve cycles.

 

[Alphasud40]

The pressure readings you recorded are fine and any heathy seal should be able to cope with that. Modern PCV design does seem to run more of a negative pressure than the order cars. They have regulating valves and PCV becomes more of an issue with everyone running low tension rings.

 

[alpineviking]

I have a suspicion that the m119 engine has one or more orifices in the valve covers to create negative pressure, like the m112. Does this sound correct? Thanks

 

[alpineviking]

I FOUND IT!so.

I was still looking for the vacuum restrictor. was looking at a schematic for M119 breather hoses, and found the manifold vacuum restrictor that I was looking for. It is inside Plastic T fitting fitting In the hoses. (Not the Y fitting) I purchased these hoses and fittings recently from Mercedes, and found this plastic T has 01.0 mm hole drilled in it for maintaining crankcase vacuum. The factory specified a 1.5 mm orifice, I drilled it out to that size. The engine now pulls a small amount of vacuum at idle. Mission accomplished!

And one other comment to make regarding WD-40. I’ve been electrician for 50 years, and we were instructed, always avoid WD-40, because of the graphite in this compound. WD40 is guaranteed failure in electrical systems. I use electrical grade silicone spray oil with great success. It’s not as easy to find as WD40 at the hardware store. Thanks again for your input on this post…

 

[gsxr]

Yup, there is an orifice / restriction in the "T" fitting. The orifice size is different between 119.97x engines (LH, distributors) and 119.98x (ME, coil-on-plug) which I always thought was weird. One is quite a bit larger, it might be the .98x?

Odd thing is, I thought the orifice / restriction was for the side port of the "T" which connects to the 8mm OD black pipe for the carbon canister purge system. I thought the connection between the 2 intake manifold suction ports (hose 131 and 134 in diagram below) were fully open to the driver valve cover port (hose 125+122).

.97x T fitting = 119-094-02-12
.98x T fitting = 119-094-06-12

 

[alpineviking]

Greetings...

One more thing that isn’t far off distributor subject. Why is it recommended to change distributor rotor brackets to newer style?

Thanks for you attention...Jim

 

[gsxr]

One more thing that isn’t far off distributor subject. Why is it recommended to change distributor rotor brackets to newer style?

The very old/originals didn't work with the new/later style rotors. This was in the early 1990's, and pretty much every M119 still on the road today would have had the rotor bracket upgraded long, long ago.