Anyone with an M20 who thinks they have an oil or air leak (ie older 525i and 325i)

[genphreak]

If you have a an e30 325, and e28 or early e34 525, you need to be aware that your engine could after some years, develop a mysterious inlet manifold air leak. This will be hard to find unless you know about it. It will degrade performance and economy a surprising amount and may also present a slight but continuous oil leak on the Left side of the engine, when the engine is running.

So here's how to check your oil pipe for leaks:

http://img342.imageshack.us/img342/7575/P1010315.jpg

You've probably never seen it before unless you are used to taking take your engine apart. All M20s have this 3/4" pipe, and you can find it in the online ETK. It connects the underside of your inlet manifold to the air in the sump to allow ventilation of fumes from the oil up into the valve cover. This way they can get sucked into the throttle body and burned up by the cylinders before they leak out and kills people (it is largely carbon monoxide).

If you have monkey arms and a high resistance to pain, you can reach in with one hand and push the pipe down against the pressure of the spring without removing the manifold, allowing you to change the upper O-ring. However, the lower one tends to go as well so that is only a quick fix. It is better to pull the manifold as shown above and get this absolutely right.

It looks to be a common cause for unmetered air getting into the head as the O-rings go bad after many years of service. Air that is normally sucked through the AFM and throttle body, can end up being sucked by these faulty O-rings instead. It will make your car run badly (the ECU doesn't know and will make the wrong combustion adjustments), making matters even worse.

See below for pictures and explanations... I found on e30tech.com. It is a cheap, but difficult fix (like almost everything else on a BMW):

Parts
Top of pipe requires
intake gasket, (these numbers are for m20b25)

02 GASKET ASBESTOS FREE x1 11611726012 $4.85
O-RING x1 11151714390 $1.25

Bottom of pipe requires
09 O-RING x1 11151714390 $1.25
10 FLAT WASHER x2 11151280937 $0.57

and a new spring?
12 COMPRESSION SPRING x1 11151265346 $1.61

See here;
http://e30tech.com/forum/viewtopic.php?t=39968&highlight=&sid=d73d18680332abc862592dd8c237f8a0

and

http://e30tech.com/forum/viewtopic.php?t=29173&view=next&sid=8f028aaca316310ad54724381fe0e05b

From these threads-
"There is a simple trick: Place a zip-tie through the spring to compress ... makes it easy to do. When reinstalling ... place in position and cut zip tie off. Make sure to clean area around lower washer and tube before removing. When you pull the tube this crap will fall into the motor otherwise ... not where you want it to go. Also, lube the O-rings on reinstall ... will slide right in. And, if you are anal like me ... replace the lower washer with new or / like kind. Mine was a rusted POS when I got in there. "

Awesome stuff compliments of the E30 crew over at e30tech.com

[winfred]

the bottom is not really much of a problem as it's usually sealed by all of the crud build up, so much so you usually need to pound it down into the block to get the intake off, which is sometimes handy as the crud will hold the tube down, oil flows though that tube too so it's clean it's probably not leaking, one tip to get the top o-ring seated is to twist the tube while pulling up and it will pop into it's groove

[genphreak]

the bottom is not really much of a problem as it's usually sealed by all of the crud build up, so much so you usually need to pound it down into the block to get the intake off, which is sometimes handy as the crud will hold the tube down, oil flows though that tube too so it's clean it's probably not leaking, one tip to get the top o-ring seated is to twist the tube while pulling up and it will pop into it's grooveThanks Winfred. We got this done and it makes a difference in the engine perfromance. The oil leak is gone... but removing the oil cap at idle still indicates no positive ventilation in the damned thing.. idle doesn't change at all in feel or speed when one does. Damn it, more hunting needed!

[bones]

yikes,no offense but that block and starter look like they were recovered off the bottom of the red sea.do they salt the roads where you live? im hoping this isnt the color of your radiator coolant.

[bones]

Thanks Winfred. We got this done and it makes a difference in the engine perfromance. The oil leak is gone... but removing the oil cap at idle still indicates no positive ventilation in the damned thing.. idle doesn't change at all in feel or speed when one does. Damn it, more hunting needed!
check the o ring packing on your dip stick tube.mine wasnt even installed.where the extension tube enters the block there should be a o ring with a really snug fit. bones

[Anton CH.]

That looks like something you picked up at Home Depot.