As many of you know, I’ve been working on a seals solution for the 6-cylinder double vanos failure. This vanos is found on engines M52TU, M54, M56, years 98-06. I’m now ready to sell a vanos seals repair kit. I started a company and created a website to facilitate sales and support; Beisan Systems (be-san),, contact [email protected]

- Background
Loach and I worked to diagnose the vanos failure and assessed it was due to deteriorating piston seal O-rings. Here is the post where we made this information public,
The piston seal O-rings are hardening, shrinking, and having flat top and bottom surfaces. This causes the vanos piston seals to fail (leak) and for the vanos to malfunction. We pursued BMW regarding the problem, but they elected to not address it, “No further development will be done”. BMW still sells new (rebuilt) vanos units with the same failing O-ring material. Owners are not failing EGR (exhaust gas recirculation) emissions tests, so it would be difficult to pursue BMW through the US EPA (environmental protection agency). In the end, it seemed the remaining viable path was to reverse engineer a seals solution.
The vanos piston seals are a combination of an outer Teflon seal ring and an inner supporting (energizing) O-ring. It is not practical to replace the inner failing O-rings without removing the outer Teflon seals. It is not practical to remove the Teflon seals without damaging them. Thus replacing the O-rings necessarily requires replacing the Teflon seals. The Teflon seals are significantly more expensive than the O-rings and need to be semi-custom manufactured.

- Acknowledgments
Several owners helped launch this redesign effort. Notably, “TR - ’95 318i – ’00 528i” was able to have O-rings from a new BMW vanos professionally tested for material content. Tony540ia contributed significantly to this effort. He inspected a used vanos and verified the failure mode. He inspected a new vanos and determined the O-ring sizes and Teflon seal type. He measured the vanos piston and cylinder dimensions and generated a schematic. He located a seals company that could manufacture the seals. He has provided extensive advice throughout this effort.

- OEM O-ring material
A new BMW vanos unit was purchased and piston O-rings removed from it. The O-rings were tested by an O-ring specialty company for material makeup. It was found the O-rings are made from Buna-N (NBR, Nitrile).
An FT-IR Spectroscopy test was performed;,
The following are the test result graphs: small O-ring, large O-ring.

- OEM O-ring failure mode
O-rings usually fail from chemical incompatibility exposure, temperature over exposure, and compression set which is directly related to temperature exposure. From inspection, it appears the O-rings are failing mostly from temperature over exposure. Chemical incompatibility exposure will cause O-rings to swell, while temperature over exposure will cause O-rings to harden and shrink. The OEM O-rings have been found to lose their elasticity and harden. Some O-rings have been found to turn into plastic and easily break when flexed. There is some indication of swell, but this is mostly overcome by the hardening and shrinking. The O-rings are also experiencing significant compression set. Compression set is O-ring deformation caused by compression and temperature exposure. This manifests in flat spots at the top and bottom of the O-ring where the compression takes place. Compression set has a direct proportional relation to temperature. The higher the temperature the higher the compression set. The OEM O-rings’ significant compression set is caused by temperature over exposure.

- O-ring solution
Many seal experts were consulted regarding the OEM O-rings failure and they consistently recommended Viton as the solution. Viton (Fluorocarbon, FKM) is an O-ring material with similar mechanical characteristics to Buna, but is significantly more resistant to chemicals and temperature. Buna-N is rated to 100C (212F) and is not compatible with synthetic oil. Viton is rated to 204C (400F) and is compatible with synthetic oil. Viton has notably improved compression set over Buna. Buna-N and Viton are the two major O-ring materials used in vanos type sealing applications.

- Teflon seal solution
Removing the OEM Teflon seal rings, to replace the underneath OEM O-rings, necessarily damages the Teflon seal rings. Thus the Teflon seals also need to be replaced. Teflon (Polytetrafluoroethylene, PTFE) is not usually employed in its virgin form (white). To increase resistance to wear and deformation, fillers are introduced. Teflon seal fillers can be mostly denoted by the color of a Teflon seal. The OEM Teflon seals are black and this indicates carbon filler with a possible small amount of graphite filler. The OEM Teflon seals were tested for filler content by a Teflon seals resins manufacturer company. A small weight-measured sample of an OEM Teflon seal was burned to assess the filler content. The PTFE vaporized at ~550C, and the remaining residue was the filler. From this test it was determined the filler is a 20% content. The filler residue was then inspected under a microscope and compared to known fillers. It was determined the filler is carbon. Although it was noted the carbon filler was not “standard”. The following is the burn test result graph: Teflon seal burn.
Several seals experts were consulted regarding the Teflon seal filler. It was recommended to use carbon as the filler. Pigment modified (essentially virgin Teflon) and graphite fillers would be susceptible to wear. Glass/moly and bronze fillers would be susceptible to damaging the vanos aluminum cylinder walls. Carbon has excellent resistance to wear and deformation, but is soft enough not to damage the aluminum cylinder walls. A standard carbon/graphite (23% / 2%) filler was chosen for the replacement Teflon seal rings.

- Piston bearing cap O-rings
The vanos pistons also utilize a small plastic cap to seal off the piston center bearing after the piston / splined shaft bolt is installed. The plastic cap incorporates a small O-ring. This O-ring has been found to wear in the same manner as the piston seal O-rings and thus is expected to also be made from Buna. The plastic caps can be purchased separately from BMW, but the new cap O-rings are also likely made from Buna. Thus cap O-rings will also be provided for replacement and will be made from Viton.

- Standard seals design
The vanos seals are a standard seals design, and thus can be manufactured to the same specification as the BMW OEM seals.

- Vanos seals configuration
The vanos incorporates two identical pistons. Each piston incorporates two seals of two sizes. Each seal incorporates a Teflon seal ring and an O-ring. Thus the vanos pistons utilize 2 Teflon seal rings and 2 O-rings of each of the two sizes (4 Teflon seals, 4 O-rings).
Each piston also utilizes a small plastic bearing cap w/ O-ring. Thus an additional 2 small O-rings are utilized.

- Vanos seals repair kit
A vanos seals repair kit was created. It includes 4 piston Teflon seals (2 of each size); 4 piston O-rings (2 of each size); and 2 piston bearing plastic cap O-rings.
The Teflon seals are of carbon/graphite (23% / 2%) filler, and the O-rings are of Viton.

- Seals installation tools
Teflon seals are best installed with special tools. There are essentially two tools for each seal size. One tool, the loading mandrel, a cone shaped tool, allows for stretching the seal evenly over the piston rim and dropping the seal into the piston groove. A second tool, the resizing tool, a cylinder with a long chamfer (bevel), compresses the seal back to its original size after loading. A small batch of tools were built, but it was assessed the tool costs are not practical, especially given reasonable non-tool alternative installation methods.
Tools are usually built to facilitate large volume production installations, but for small numbers of installations, alternative methods are often employed. A Teflon seal can be stretched over a piston by hand and possibly hand tools, and can be resized by the cylinder it operates in. Non-tool techniques have been optimized for the vanos seals installation, and have been found to be quite practical.
Mechanics performing multiple installations might be interested in acquiring installation tools to simplify the installation process. Consideration for building and providing tools will depend on mechanics’ feedback and requisition.

- Installation procedure
A detailed vanos seals installation procedure was developed and is provided for reference. Most of the repair procedure is independent of car model. But there are some specifics that deal with removal of components surrounding the engine to facilitate access that are model specific. The procedure currently addresses the 5-series E39, and 3-series E46 with electric fan. The procedure will continue to develop, adding specifics for the different models.

- Seals break-in
When new, Teflon seals will have a rough milled surface. After a period of use, the contact surface will be polished and have lowered contact friction. Thus at initial installation Teflon seals will not perform well, but their performance will increase progressively in a short period. Optimum performance can be expected after ~500 miles (800 kilometers) of city driving.

- Purchase and shipping
The vanos seals repair kit price is $60. It can be purchased through the website. Shipping cost is $5 for domestic (US) shipping, and $20 for international (non-US) shipping. The shipping charge is per order and is independent of the number of seal kits purchased. Shipping will be via US Postal Service Priority Mail; 2-3 days domestic, and 6-10 days international (3-5 days Europe). The website shopping cart and payment processing is provided by PayPal. US North Carolina residents will pay local and state taxes, currently set at 6.75%. International residents will be subject to customs duty/tax which is usually paid through the postal service.

- Support
A postal address, phone number, and email address are provided for contact.
A vanos forum has been setup on Bimmer Board and is referenced on the website forum page. The vanos forum should be considered the primary media for support. It will contain questions/answers, discussion, feedback, technical information, FAQ, etc.

- Performance test results
Many dyno (dynamometer) tests were performed with and without load to assess the performance differences between failing vanos pistons, new vanos pistons, and repaired vanos pistons. Unfortunately the test results have been inconsistent. They also do not show the performance improvement gains. Owner feedback will need to be relied on for performance assessment until a more scientific method can be attained.

- Fuel consumption test results
Highway fuel consumption tests were performed to assess the consumption differences between failing vanos pistons, new vanos pistons, and repaired vanos pistons. A 20 mile section of highway served as the test track. The test highway section is quite hilly. Tests were performed at night to facilitate lower temperature, low traffic, and no air conditioning. The car OBC was used to attain the MPG fuel consumption. The cruise control was used and set for 70 MPH. Consumption was tested in both direction of the highway test section.
No noticeable difference in fuel consumption was attained between the differing pistons/seals. The average consumption of the round trip was ~34 MPG.
It is not practical to perform a well controlled city driving fuel consumption test. None were attempted.

- Long term testing
To perform long term testing in a short period, multiple cars would need to be driven continuously to various mileages and then have their seals removed and inspected. This is not practical.
As an alternative, owner cars will be utilized for long term testing. After installation, a defined mileage will be driven, then the seals will be removed and inspect. Inspection mileage durations will be 20, 40, 60, 80, and 100k miles. Owners living in Raleigh, NC are requested to participate in this testing. Initial and inspection repairs will be performed at no cost.

- Cold engine idle problem resolution
M52TU engine cars are experiencing cold weather cold start idle jolts and possible stall. This occurs when the DME utilizes the vanos to help bring the cats up to operating temperature faster. The seals repair kit resolves this problem and other vanos related idle inconsistencies.

- Lower RPM (< 3K) bogging and hiccupping problem resolution
All cars with the failing vanos will experience a lower RPM torque and power loss. The car will bog and need to shift into a lower gear. Hiccupping, also felt as hesitations, will be present at lower RPM’s. The seals repair kit resolves these problems, and provides an over all increase in torque, power, and a smoother transition throughout the RPM range.

- Fault codes
Cars are beginning to experience vanos failure fault codes. The fault codes are all related to the vanos exhaust side. There is a spring in the vanos exhaust cylinder that advances the exhaust piston by default. This facilitates advanced exhaust timing at startup to assure no intake/exhaust valve opening overlap. To retract the piston takes a great amount of oil pressure. Due to the leaking piston seals this pressure can not be achieved and the piston can not be retracted properly. The fault codes all relate to this scenario. The following is a list of the fault codes experienced. The seals repair kit resolves these codes.
P1520 (BMW 104, 0x68): B (exhaust) Camshaft Position Actuator (faulty reference value).
P1523 (BMW 106, 0x6A): B (exhaust) Camshaft Position Actuator Tight or Jammed (mechanically stuck).
P1397 (BMW 18, 0x12): Camshaft Position Sensor B (exhaust) Circuit.
The Camshaft Position Sensor (CPS) is a common failure. But if replacing the exhaust CPS (w/ OEM CPS) doesn’t work then it’s likely the vanos failure.

- Beta installations
Seven owners have volunteered to install the seals solution and provide feedback. They have performed their installations successfully and will be providing feedback on the vanos forum.

- Mechanics
Although the vanos seals repair can be a DIY repair, most owners will not undertake this repair themselves. Independent mechanics will be needed to perform the vast majority of the repairs. Independent mechanics will also be the conduit for reaching the many owners who are unaware of their vanos failure.
It is requested that if an owner performs the repair and is please with the results, that he/she consider sharing this with their local independent mechanic(s), and/or provide the shops’ contact info.
Mechanics should be pleased to have the vanos repair option. It will provide them a stream of 4 hour uncomplicated repairs, and their customers will be quite pleased with the performance enhancement results.

- Owners feedback
Owners are encouraged to post feedback on their experience at the vanos forum. It is best to wait until the seals break-in and optimum performance is achieved. Owner feedback will be valuable to other.

- Company name
Beisan, pronounced “be-san”, is the name of a town in historic Palestine that my mom and grandparents come from. The name is meaningful to me.
528i 5sp 06/00