E30 Oil Control Valve Gasket Leak
M20/B25 Engine

Prepared by VietSB
Modified 05.22.02

NOTE: Perform these steps at your own risk. All P/N's listed are a "best guess", so please double-check with your local dealer. These mods and repairs were performed on my US-Spec 1989 325i (12/88 prod date, M20/B25 engine) but there is no guarantee they will work on other E30's. These instructions are provided for entertainment purposes only!

BACKGROUND: On E30's with the 6-cylinder M20 engine and oil cooler (B25 variant), BMW includes a control valve on the underside of the oil filter housing (see red arrow below). The valve used a faulty O-ring material and was later replaced in 11/90 with a better quality material called Viton, outlined in BMW Service Information bulletin 11 09 90 (3137). After seeing a number of posts regarding this common and annoying oil leak, I decided to document the fix.

In my case, it would cause a drop or two to come down every other time I turned off my engine, but only on the passenger-side. The dipstick reflected about a 1 quart loss in between oil changes. Since I didn't see 1 quart's worth of puddles, I assume most of the oil leaked while driving, when the oil system was under pressure. Post-fix, my car (127K miles) is showing no noticeable oil consumption/loss.

It's often difficult to spot this slow leak because it won't leave a lot of evidence as to the exact source. While driving, it will deposit oil onto the area around the oil pressure sensor. Originally, I saw oil pooling up at the bottom of the sensor's wiring and thought to replace the sensor and gasket. I ended-up crawling underneath, cleaning off all the oil, and letting my car sit above a piece of newspaper. After short idle, I shut it off, waited 15 minutes, noticed a drop come down, and traced it upwards to the control valve. A quick swipe with a napkin showed oil just inside the lip of the control valve. After reading some posts and quizzing a couple of folks on this great board, I found it was a common issue that could be fixed relatively easily and cheaply.

1. Parts you'll need:

2. Remove the oil filter and clean around the entire oil filter housing area.
3. Place the C-clamp around the oil filter housing to clamp the valve cover in place inside the housing. Be sure the clamp is secure (but not too tight) since it will keep the spring-loaded control valve in place when the snap ring is removed. Failure to do so properly might result in parts raining down on you at high speed...
4. Carefully remove the snap ring by prying it out using the screwdriver. I found this to be the most difficult part. Avoid damaging the filter housing lip, as it can be easily chipped during the prying. As you can see by the picture below, the new snap ring is knurled on both ends to make installation and removal easier via pliers.

For reference, the threaded bolt towards the upper-middle of the picture is where the oil filter screws onto, and the wire harness to the left is the oil pan level sensor.

5. Carefully release the C-clamp and collect the following parts: snap ring, valve cover, faulty O-ring, spring, and thermostat. Pay close attention to the parts removal order as they will be reinstalled in the same manner. A small amount of oil will normally drip when the valve cover is removed.
6. Clean excess oil off the spring and thermostat using a shop rag. Install the replacement O-ring onto the new valve cover and proceed to insert the parts in reverse order. Securely clamp in place w/ the C-clamp and install the new snap ring using the pliers.
7. Remove the C-clamp, check the positioning of the valve cover and snap ring, run the engine for a minute, then check for final leaks. Hopefully, you are done!
Some of this information might also apply to the S14 M-Power engine, but since I don't own a M3, I can't verify it. The S14 does use a different valve cover, so only the O-ring and snap ring need to be replaced.

Questions? Comments? E-mail me: .

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