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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 7 Series / 8 Series > 7 Series - E38 (1995 - 2001)

7 Series - E38 (1995 - 2001)

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Old 02-12-2013, 10:41 PM
Dakota89 Dakota89 is offline
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Location: Sequim, WA
Join Date: Nov 2012
Posts: 5
Mein Auto: 99 740il
99 740il Cheap, semi-permanent cure to huge cloud of smoke at startup

Hello everyone im new to the forums i just thought id share a new cheaper and easier fix for the common broken oil separator usually not found out until the new crancase vent valve on the back of the intake doesnt cure your smoke problem. Heres a little background. I was fed up because i recently tackled an engine swap as a cheaper alternative to fix all the issues with my engine. After dropping the new engine in i found that the cyclone oil separator neck was broken and that i would have to replace it meaning hours and hours more work.

Prior to my head gasket failure and engine swap i tried to cure the huge embarassing plumes of smoke coming out my exhaust pipe at home, at work, at the supermarket, at every social occasion you would want to make an elegant exit. Anyways i got for 100 bucks a bmw oem crankcase vent valve and went to swap it in. I noticed for one the vent tube needed replaced due to the cracked rubber but also inside where it sealed into the block seemed loose and would rotate around feely. I thought it was fine because the o-ring would seal in any direction and it didnt seemed to rattle around or anything but alas the smoke was worse when i was done.

Reading about having to remove the cyclone oil separator and taking the crank pulley and lower timing cover off after i just swapped in the engine and connected all that stuff got me thinking there has to be an easier way. Using my spare engine as a guinea pig i was determined to fix it without pulling the lower timing cover and having to reseal everything. The trick is that there is a 90 degree fitting attached to the rest of the COS housing via the flimsiest plastic hose you have ever seen (which is where the failure is 115% of the time), and LUCKILY a length of about an inch or so of heater hose and lots of napa sil-glide to protect the rubber from oil vapors allows you to retrofit some real rubber into the flimsy plastic stock design. Mine of course had only bits and pieces of the plastic hose left because when it breaks it shatters to pieces. Im sure if your budget included more than lint and popsickle sticks then you could buy a more oil resistant hose for a not-so-semi-permanent fix.

You have to remove your intake ducting, throttle body, coils, wiring+fuel rail (tie up out of the way), drivers valve cover, egr valve+tube, and drivers vanos solenoid or waterpump to make clearance for finally removing the upper timing cover. You can pop the vent tube out from the front without having to take off the intake. My tube was new and the o rings were sil-glided up so it popped out easy. Back out the set screw holding the fitting in and your done with the disassembly. Its all easy cheesy from here. Or is it...?

Now i spent half the whole job (disassembly and reassembly) trying to get the hose in and the trick is to rattle that 90 degree fitting around until you find the odd angle where it sits almost out of the way. Once you get the fitting almost out of the way you can squish your length of heater hose flat and squeeze in in between the block and the timing chain guide straight down on top of the COS. Using a long pick you can work the edge of the rubber over the neck and using a huge flathead i crammed it downward. On my guinea pig i got the pick just right and pushed the hose down while sliding the pick in a cicular motion. It seemed to pop in place and when i pulled the pick out i was able to seat the hose down on the COS neck with ease. On my currently installed engine it wasnt so easy (the pick hits the intake and you have to remove the throttle body for clearance) and i had to use a scary amount of pressure with the screwdriver to seat the hose.

Once you get the hose down on the COS its not so hard to squeeze the fitting in place and retighten the set screw. My new engine was missing the set screw that holds the fitting against the block (no wonder the neck broke) but i had a spare! Be careful not to tighten the set screw down too tight as it levers the timing chain guide away from the block. Now on to the reassembly! The only real thing worth noting during reassembly is that you have to hand tighten the upper timing cover bolts, then install the valve cover and torque all the valve cover bolts. This presses the upper timing cover down and seals it against the lower timing cover. You can now torque your timing cover bolts and remove your valve cover to double check the fit (if you deem it necessary.) The last person to work on the engine before me used gasket maker instead of following these instructions so i had some rubber to chisel off the sealing surfaces but once i got it all installed it fit perfect. Someday ill fix the passenger side. :P

I hope this saves someone some time and money. My thoughts were that the stock timing chain guides were on their way out already at 102k and i just had to buy myself some time before i was tearing it down anyway. At 40 bucks on pelicanparts the cyclone oil separator itself isnt expensive but theres alot more work there. I figured i can be lazy and i have at least 5 years before that rubber starts to dry and crack. Im sure ill replace it before then.

The results? NO smoke! No more engine choking on oil, no more embarassing cloud tracing me back to my house or parking space! Since i only started the car once with the clean intake, new engine and bad COS it only took one startup to clear the residual oil out and i havent seen a tiny puff since. Now to fix the shuddering torque converter clutch!

Now I took a few pictures of before and after i got the hose in place, if you need a visual aid im sure i can email them to you or something. Like i said, im a newbie here. Happy trails!

Last edited by Dakota89; 02-13-2013 at 12:41 AM. Reason: Proofreading
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Old 02-15-2013, 09:45 AM
jitsjaf2009 jitsjaf2009 is offline
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Location: Hemet, Ca
Join Date: Aug 2012
Posts: 442
Mein Auto: 1995 325i Convertible
Autohaus.com has the oil separator for $33.99 plus another couple bucks for o-rings. I was able to change it myself.
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Old 02-15-2013, 10:21 AM
Dakota89 Dakota89 is offline
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Location: Sequim, WA
Join Date: Nov 2012
Posts: 5
Mein Auto: 99 740il
Oil Separator

Glad to hear there is a site cheaper than pelicanparts but as i said before its not the price of the part that makes the job unrealistic, its the amount of work required. By using this method i got to save myself like 8 hours of labor and breaking my back on a 400ft lbs crank bolt. To tell you the truth knowing what i know now i dont see why anyone would replace the osv (as opposed to repairing it) unless they already needed it taken down for new timing chain guides.

In fact ill go a step further to say i would deliberately not change my osv knowing that the factory design is poor and that i increased the lifespan of the osv tenfold. Besides i think i would rip my hair right out of my head if i spent 8 or so hours exchanging the osv to have it snap a year down the road when changing intake manifold gaskets or something similar. The fact is the plastic neck on these oil separators is not designed to last in an oily environment with flex and vibration. At the least i can say the standard oil soaked rubber hose doesnt shatter into 10 pieces when you flex it like the plastic does.
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