View Single Post
Old 02-27-2012, 09:13 PM   #1
Registered User
Join Date: Apr 2010
Location: Chicoutimi, Quebec, Canada
Posts: 102
My Ride: 325xiT and E30S50
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:


Last edited by MatRacer; 02-28-2012 at 12:29 PM.
MatRacer is offline   Reply With Quote
Ads by Google

Guests, get your FREE membership to remove this ad.