E46Fanatics (http://forum.e46fanatics.com/index.php)
-   DIY: Do It Yourself (http://forum.e46fanatics.com/forumdisplay.php?f=27)
-   -   DIY: OE Oil Separator alternative --> E39 M5 OS (http://forum.e46fanatics.com/showthread.php?t=906116)

MatRacer 02-27-2012 09:13 PM

DIY: OE Oil Separator alternative --> E39 M5 OS
Hi everybody!

I have been having problems with my OS for about a year due to cold weather in winter. Here it goes down to -22F a couple of times a year.

My OS was freezing, causing the pressurisation of the crankcase. My valve cover gasket was then letting oil out, directly on the exhaust manifold... Lot of fumes.

After the installation of the Cold climate version of the OS, I tought that it would stop my problem, but it didn't. I also tried a German brand engine cleaner. You put this in your old oil before flushing it, you let run the engine for 30 min, then flush. It is supposed to remove moisture and **** from the oil system. But it was still freezing. I also Tried the trick of "vintagegz" IE removing oil cap when arriving home to let the moisture out. It helped, but with out success, it froze again.

The only way I manage to avoid the the OS to freeze in extreme cold was to drive the car in a way to created the most pressure variation in the intake so the diaphragm of the OS can open and close frequently. THis worked, but was hard on gas mileage...

I finaly decided to swap the OE OS with a E39 M5 OS and to fit it like on a M5. Our Orginal OS is sending the oil vapor (and moisture) directly in the intake. THis is better since the fumes don't go thru the Throttle. However, you must have a diaphragm in the OS to avoid to much vacuum leek. From valve cover to OS. OS to Intake, in between MAF and Throttle. Since the M5 has 8 throttle bodies directly on the heads, its impossible to do so. There is two OS, centrifugal type, that return the fumes in the intake, before the throttle bodies.

Here is the E46 system:

With the item #5 being the vacuum distributor on the folling schematic:


The E39 M5 system:

What I did is:

1- Removed the E46 OS hoses, except the one from the OS to the didstick (item 4) tube since I resused it. I kept the Connector of the hose #2 since I resused it to plug my hose to the valve cover. After trying to disconnect the hose #2 from the OS for about 45-60mins, I cut the hose and decided to leave the OS in there. Keep in mind that cold climate version is thighter

2- I left the vacuum distributor in place and caped both hoses ports. Some people are removing the vacuum distributor and are capping the 6 ports with 3/4 vacuum caps.

3- I used 3/4" oil resistant hose (aeroquip) to plug the valve cover to the OS, part #11151406789, item #2 on E39 Schematic. I resused to original connector for the valve cover. Plugging the 3/4" 250psi on the M5 OS was a pain. The hose was to rigid.

4- I replace part #13541435626 with my vacuum port adapter that I had previously got machined. I used the same 3/4" hose to route the output of the OS to the intake tube.

5- The Drain of the M5 OS, is directly plugged to the Dipstick tube with the original hose.

6- Reassembled the rest.

7 - DONE!

I Did around 1000km with that setup without an issue! I looked at my throttle afte a week of extrem cold, and there was a bit a water. My only concern is about the Throttle that could eventualy freeze. I will modify the routing from the OS to the vacuum adapter so the melting condensate will flow to the OS and then to the oil pan, not to the throttle. My downward section of this hose is a bit long. I will add an elbow.

For the cleaness of the Throttle, I don't think it will be an issue, since the M5 is running like that. A lot of other cars are also running like that. Anyway, I will keep an eye on it.

Here are the pics:

Intake adapter for vaccum pickup (connection of the exhaust of the OS)


Setup of the OS


Final look


I think It would be hard to fit with the original air box since the vacuum adapter is spacing the two intake flex tube a bit, maybee an inch....

Here are two reference threads:



fastjasonbmw 02-27-2012 09:28 PM

In for future pic of throttle body after some miles. Looks good though!

MatRacer 02-28-2012 12:30 PM

Update! More details

Drewfus2101 02-28-2012 02:10 PM

Good post.

Did you use a PCV valve as a check valve between the dip-stick and OS?

Drewfus2101 02-28-2012 02:11 PM

And VERY nice adapter for the intake.

MatRacer 02-28-2012 03:36 PM


Originally Posted by Drewfus2101 (Post 14130257)
Good post.

Did you use a PCV valve as a check valve between the dip-stick and OS?

No, I just connected the original hose to the bottom of the M5 OS.

And thanks drewfus! I measured the plastic original part and draw the adapter. I can provide the drawing if required.

TerraPhantm 03-02-2012 01:57 AM

About the cleanliness of the throttle - wouldn't the M5 having ITBs change things?

Drewfus2101 03-02-2012 09:11 AM


Originally Posted by TerraPhantm (Post 14140766)
About the cleanliness of the throttle - wouldn't the M5 having ITBs change things?

Change things how? Do you mean that they would just spread around the oil vapors? So individually, they wouldn't be that dirty. But with us only having one, it will be dirtier.

I saw a DIY on the M5 site about changing the OS, and it had a good picture of the intake manifold. It had a good deal of oil vapor in it, but with their ITBs pointing up, the vapor seemed to pool more in the manifold.

So the e46 setup will suck in more vapor, but no more than the stock CCV setup. And I don't see any way that it could harm the TB. If I did this, I'd pull it apart and look at it real well after a few hundred miles though, just to be sure.

MatRacer 03-02-2012 10:09 AM

The only thing I see that can harm the TB is the water created be the melt of the rime that is initialy created in the OS pipe in cold weather. This water could freeze the throttle. I experienced extreme cold weather without any issue so far.

Anyway, I want to reduce the downward section of my tube between the OS and the intake tube.

fadeaway 05-01-2012 04:38 PM

Hi MatRacer :hi:

Any updates?

Any problems with the difference in pressure regulation mentioned in other threads?

Sweetness 05-09-2012 09:16 AM

Update on how it's holding up

fadeaway 05-10-2012 05:24 PM

Instead of creating a brand new aluminum fitting between intake boots, would it be absolutely absurd to Y-pipe into the vacuum fitting or whatever that thing is on the lower intake boot?

Drewfus2101 05-11-2012 11:17 AM


Originally Posted by fadeaway (Post 14381325)
Instead of creating a brand new aluminum fitting between intake boots, would it be absolutely absurd to Y-pipe into the vacuum fitting or whatever that thing is on the lower intake boot?

Upper or lower? Either way, I think so.

The upper has the 'F' tube, which constantly breaks and is too small for the oil fumes and would clog quickly.

The lower has a 'Y' that connects to the idle air control valve.

Either way, your having to connect rubber-to-rubber. I've done this for my catch can, and it never works well or for long.

The custom adapter is the best way to do this. You ***might*** be able to modify the OEM plastic piece between the upper and lower boots with a plastic adapter piece to make it work like this custom adapter.

fadeaway 05-11-2012 11:41 AM

You mean part number 5 here, right? I thought about this as well. I would assume that the vacuum for both the F connector and ICV is such that nothing will get sucked into it. If so, I would think that modifying part number 3 would allow for the most clearance for a new connector. This entire assembly has pretty cheap parts.


Hansie 04-26-2013 06:37 AM

Great mod!
I'll copying this adaptor but start using an catch can with filter mesh (got that already), maybe later the M5 part.
Hopefully I filter out most of the oil.

My problem was almost the same : lots and lots of moisure in my CCV because of short drives (below 30km) in cold/wet weather.

Diazz 06-19-2013 04:58 PM


I decided to do exactly this setup on my 325Ci, m54b25.

Just did the yearly inspection and:
Carbon monoxides = 0
Hydrocarbon = 0

If this says anything to you?

Last year with stock CCV i got:
Carbon monoxides = 0,1
Hydrocarbon = 49

Anyhow, so far the system is running great!

my323coupe 06-23-2013 08:21 AM

AW: DIY: OE Oil Separator alternative --> E39 M5 OS
Can you please show a pic of your intake manifold?

Sent from BimmerApp mobile app

Diazz 07-05-2013 11:35 PM


Originally Posted by my323coupe (Post 15522048)
Can you please show a pic of your intake manifold?

Sent from BimmerApp mobile app

Sure, but what part? the intake manifold is stock, i only plugged the hoses to the original CCV

Hansie 01-07-2014 03:34 AM

Just an update :
I dont collect any oil, water with a few drips of oil.
In 2000km the catch can is almost filled with water !!
All that moisture in the oil will be sludge/mayo and block the stock system.

I made an extra tap in the bottom with a very small hole, water can slowly drip out but not a lot of air can be sucked in to ruin feuling.
Offcourse those drips contain minimal oil and is bad for the envoirement but so is the powersteering fluid and other minimal leaking VCG's etc.

Hansie 03-16-2014 03:55 AM

After 10k km with a catch can , vented to the plastic ring between the rubber parts in the intake.

Short : nono!
There is simple not enough flow and vacuum at all rpm. Tube from cylinder head got mayood very rapidly and pressure build up.
Bye bye vcg and hello oil leaks.

Now changed to catch can and full vacuum from distribution piece....

That's my story, remember : cold around 5 degrees C and very humid, so lots of condensation in the system.

If that doesn't work, back to oem and give the car to the misses 1x / week. She drives longer distances.
I have to fold myself in the Z3 then...

All times are GMT -5. The time now is 12:47 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
(c) 1999 - 2016 performanceIX Inc - privacy policy - terms of use