Oilhead Tech Pages

Fixing Oil Filler and Cam Cover Leaks

Stephen Karlan (Dali Meeow  -  dalimeeow@comcast.net

If you own an R850 or R1100 BMW and there is excessive grime or some messy oil leaks around the oil filler cap or the black plastic cam covers at the rear of the cylinders, then your bike might benefit from some high temperature O-rings. The original O-rings are made of soft materials and will deform after extended use and heat.

The solution is two-fold. While you are changing O-rings, also check the plastic for any casting flash. This hint comes from Rob Lentini, who suggests that you run your fingers over the inside of the plastic parts and feel for bumps or rough spots created when the parts were made. Many plastic parts have this bump or ridge and, if it has not been smoothed, it provides a path for oil to leave the engine. Take fine wet-dry sandpaper or a fine file and smooth off any bumps.

Thanks to Bob Gorman (bgorman@ccnet.com) for identifying the problem. He said, "For some reason BMW choose to use an O-ring made out of a very soft material. Over time this material will lose its 'O' and become flattened, allowing oil to easily flow around the seal." Even the Viton® O-rings will wear over time, but that should be measured in years.

The second part of the solution is to replace the O-rings with a high temperature material called Viton®. These are made for aircraft and are used in extreme conditions -- they work well in the BMW. There may be local sources for these Viton® O-rings in your area; check for a seals shop listing in the Yellow Pages. If you have trouble finding the O-rings, I will send you a set for $15.00 if you send me eMail saying that you want a set along with your name, full address and telephone number. Click on "send me O-rings" and make sure you include all of your mailing information and phone number.

STEP-BY-STEP INSTRUCTIONS:

Replacing the oil filler O-ring.

There is a black plastic ring still in the cylinder head. Locate the black tab at the rear of the ring that mates with a small depression in the cylinder head; observe this tab because you must line up the tab when you reinstall the plastic ring later. The O-ring that you want to replace is located on the outside edge of this black plastic ring; this O-ring is the only thing holding the black plastic ring in place. Remove the black plastic ring carefully by placing your pinky finger in the oil filler hole and pulling up gently or by prying it out (try a flat-head screwdriver). When it is out, use your fingers or a small flat-head screwdriver to remove the old O-ring on the outside of the plastic ring, check the plastic, and install the smallest of the Viton (R) O-rings from the set of three that you will need for this installation.

Reinserting the black plastic ring can be tricky. It is a tight fit and you do not want to crack it. Lubricate (with oil) the part and line it up (black tab) and try to push it in by hand. Repeat several times. If that does not work, install the oil filler cap back into the black plastic ring (both plastic pieces now mated) and align the black tab on the ring with the cylinder depression. Lubricate and tap gently. If you tap too lightly, nothing will happen and you will have to tap again slightly harder. If you tap too hard, you may crack the plastic ring. You are better off tapping too gently and then trying it a second or third time. In other words, be careful. Total time: five minutes.

Replacing the cam cover O-rings.

Plan to install these the same day you get them, it is that fast and easy. All tips or corrections to the instructions are welcome. Let me know if you find any damage to the O-rings you are removing so that I can update my data base.

The author has done his best to produce accurate information. However no responsibility can be accepted for any damage or injury caused by any errors or omissions in this article. Make certain that you understand what is described and why it is being done. Use at your own risk.