This information is for reference only. Use it at your own risk,
In no event shall Beisan Systems, LLC or its members be liable for incidental, consequential, or special loss or damages of any kind however caused. This includes information related to the 6-cylinder Double Vanos.
Introduction
“Vanos” is BMW’s name for its variable valve timing units. Vanos units take on various shapes and design according to car year and model (engine model).
Replacing the helical gear
Replacing the helical gear components is expensive and the gears will wear again and the rattle will return. Eliminating axial play in the Vanos piston bearing significantly reduces the rattle, often to the point where it’s barely audible or completely undetectable within the passenger compartment. Performance cams like the cams on the US E46 ZHP or aftermarket performance (Schrick) cams create stronger camshaft lash forces and thus are more susceptible to causing a rattle.
Beisan Systems
Beisan Systems provides a Vanos rattle repair kit which has a replacement component for the Vanos piston bearing to remove the bearing axial play. An associate special tool is also provided to facilitate the repair.
Below is a more detailed explanation of the rattle cause and solution.
Technical background
Understanding the BMW variable valve timing (VANOS) system is necessary to diagnose the cause of the VANOS rattle.
Variable valve timing is the modifying of the engine valve opening/closing timing dynamically. BMW’s variable valve timing implements a time shift (phase shift) scheme. While the camshaft cam itself remains unchanged, VANOS alters the timing of valve opening and closing, What changes is the time when the valve opening/closing occurs relative to the crankshaft timing.
The system modifies (shifts) the camshaft’s rotational position relative to the crankshaft. Advancing (clockwise) the camshaft advances (earlier) the valve timing (opening/closing) relative to the crankshaft. Retarding (counter clockwise) the camshaft retards (later) the valve timing (opening/closing) relative to the crankshaft.
Helical (slanted) gears physically implement this mechanism. Due to their nature, helical gears require a rotation to insert onto each other. The system utilizes the properties of these helical gears to dynamically adjust the camshaft’s rotation relative to the crankshaft while the engine is running.
The camshaft and camshaft sprocket are not directly connected.. The sprocket has a hole at its middle that’s larger than the camshaft end. The system mounts opposing slant helical gears at the sprocket hole and the camshaft end. An independent splined shaft with a cup features helical gears both inside and outside its walls. The splined shaft cup inner helical gears match the camshaft helical gears and the splined shaft cup outer helical gears match the sprocket helical gears. The splined shaft cup inserts onto and engages the camshaft and sprocket helical gears. Thus the splined shaft connects the camshaft and sprocket.
Inserting and withdrawing the splined shaft axially in/out of the camshaft and sprocket requires the rotation of a component due to the helical gears. The sprocket rotation is fixed by the timing chain. The splined shaft can’t rotate due to the opposing helical gear slants on its cup inside and outside. Therefore, axial movement of the splined shaft rotates the camshaft.
Inserting the splined shaft axially onto the camshaft and sprocket causes the camshaft to advance (rotate clockwise) and cause advanced (earlier) timing.
Withdrawing the splined shaft axially from the camshaft and sprocket causes the camshaft to retard (rotate counter clockwise) and cause retarded (later) timing.
The vanos is a hydraulic actuator. Its function is to dynamically position the splined shaft axially to cause camshaft advance or retard rotation which enacts variable valve timing.
The vanos utilizes two cylinders and a piston. There is an oil chamber at the fore and aft of the piston. Controlling the oil pressure in the two oil chambers manipulates the axial position of the piston. Seals on the piston allow the piston to reciprocate axially along the cylinder walls while maintaining a tight oil seal on the two oil chamber.
The splined shaft is mounted to the vanos piston. Thus manipulating the axial position of the piston also manipulates the axial position of the splined shaft. The piston has a bearing at its center. The splined shaft is mounted to this bearing. The piston bearing allows the splined shaft to rotate with the camshaft and sprocket while not rotating the piston.
Due to the nature of helical gears, not only does the axial positioning of the splined shaft cause the rotation of the camshaft, but also reciprocally the rotation of the camshaft causes the axial positioning of the splined shaft.
Over time and use the helical gears on the camshaft, sprocket, and splined shaft develop wear along the gear spline side contact surfaces. This wear creates excessive play between the helical gears. This causes excessive play in the fit of the splined shaft to the camshaft and sprocket.
This manifests in axial play between the splined shaft and camshaft and sprocket.
As the camshaft rotates the cam nose rolls onto the valve seat and compresses the valve spring to open the valve and rolls off the valve seat and decompresses the valve spring to close the valve.
The resistance force of the valve spring compression creates an opposing force to the forward rotation of the camshaft. The recoiling force of the valve spring decompression creates an additive force to the forward rotation of the camshaft.
Rattle solution
As noted above removing the vanos piston bearing axial play significantly reduces the rattle. Also replacing the helical gear components (splined shaft, camshaft, sprocket) is expensive and the helical gears will wear again. Thus removing the vanos piston axial play is a practical approach to addressing the rattle problem. Furthermore, per bearing specification and consultation with bearings companies, there should be no bearing axial play and a notable axial pre-load (tightness) should be present.
The VANOS piston bearing consists of a thick washer and two thrust (roller) bearings. The washer if mounted to the splined shaft and the two thrust bearings sandwich the washer facilitating the washer to rotate at camshaft speed. The washer and two thrust bearings are incased in a ring and two ring outer washers. The complete bearing sits within a piston cavity, sealed by a piston bolt/cap.
Removing the bearing axial play requires modifying or replacing at least one bearing component. Manufacturers produce the thrust bearings, a standard component, to tight tolerances. Modifying or replacing them is not feasible. However, the ring and center washer are non-standard parts, and manufacturers produce them to loose tolerances.
To eliminate bearing axial play, one can either reduce the ring height or increase the center washer height. Testing reveals significant height variation in the rings, while the washers exhibit less variation. Due to these findings, it’s more effective to replace the ring. Adjusting the bearing during installation can compensate for minor axial fit variations.
A metallurgical consulting firm assessed the bearing ring and center washer, evaluating their material composition, hardness (including micro-depth hardness), manufacturing process, and surface finish.
To address the VANOS rattle, manufacturers produce replacement VANOS piston bearing rings to the original specifications but with a reduced height and tighter height tolerances. Manufacturers produce all other ring dimensions to tight tolerances as well.
The bearing ring is a difficult and expensive component to produce. Manufacturers make it from special bearing steel and harden it to a high level of hardness. They also grind all its surfaces to ensure precision.. This technique allows for machining hard parts to a high dimensional tolerance and a polished surface.
The double vanos rattle repair kit includes two replacement vanos piston bearing rings.
Repair techniques
Replacing the piston bearing ring requires removing the piston bolt/cap that secures the bearing. This is difficult due to the need to counter hold the piston to open the bolt/cap and the small size of the piston.
The piston has fins that allow for counter holding the piston to open the bolt/cap. However, manufacturing and distributing a specialized tool for this single application is cost-prohibitive. A vise can be used to stabilize the piston instead. A standard vise would damage the soft aluminum piston. Common aluminum and rubber coated aluminum vise jaw liners would also risk damaging the piston. Testing shows that softer nylon vise jaw liners effectively hold the piston without risk of damage. Soft vise jaw liners are provided as an associate tool for the repair. The liners can also be useful for other delicate component work.
Due to the small diameter of the piston the piston will spin in the vise jaws with soft vise jaw liners when attempting to remove or install the piston bolt/cap. An impact wench easily removes and installs the piston bolt/cap without risk of piston damage. Therefore, you will need an impact wrench and impact socket to perform the repair.
Symptoms
Vanos rattle at a certain RPM range, often 1800-2200 RPM. Rattle can also occur at idle.
Manufacturers produce this VANOS unit with loose piston bearings, which means all VANOS units can develop a rattle. The VANOS rattle occurs when resonance builds up within the camshaft lash and its associated moving parts.
Some car models are more susceptible to achieving this resonance and rattle than others.
Models susceptible to experiencing vanos rattle:
3-series E46 320i, 323i, 330i
5-series E39 520i, 523i, 530i
5-series E60 530i
Z3 all models.
We will update this list periodically as more data becomes available.
Note: All models can and have experienced the vanos rattle.
Repair Procedure
The following is a double vanos piston bearing rattle repair procedure.
Perform this repair in conjunction with the double VANOS seals repair. Complete the rattle repair before installing the new VANOS seals.
Repair time: .5 hours mechanic, 1+ hours DIY.
Parts, Tools, and Shop Supplies
Double vanos rattle repair kit (BS002) $60/each (www.beisansystems.com), soft vise jaw liners (BS091) $15/each (www.beisansystems.com)
Caution: Beisan soft vise jaw liners are critical to performing repair. They are fully nylon and will allow tightening vise without damaging piston. Other types of jaw liners, including aluminum and rubber coated aluminum, can damage piston.
4″, or larger, swivel vise (Harbor Freight, 4″ at store $45)
Note: Mount vise before use
1/2″ impact wrench (Harbor Freight, http://www.harborfreight.com/12-electric-impact-wrench-68099.html on sale at store $40)
24mm impact socket 1/2″, T30 torx bit socket 1/4″, 90 degree pick tool, magnet pickup, 1/4″ ratchet
Paper towels, brake cleaner, oil spray
~400 grade sandpaper (not shown)
Repair
Perform the repair after removing the VANOS unit from the engine and detaching the VANOS cylinder covers. Refer to double vanos repair procedure.
Replace vanos piston seals after this procedure.
For each vanos piston perform following procedure.
Removal of piston bearing
Clean vanos piston (brake cleaner & towels).
Install piston onto engine intake splined shaft with piston mounting bolt; left hand thread (T30 torx bit socket 1/4″ / 1/4″ ratchet & extension).
Lightly tighten.
Inspect piston bearing axial play.
Hold helical shaft and tilt (rock) piston to each side to note bearing axial play (free space).
You can also check axial play by repeatedly inserting and withdrawing the piston in and out of the splined shaft.
Note: Radial play, which refers to side-to-side movement, is normal and necessary. Do not confuse this with axial play, which involves in-and-out movement.
Remove piston and piston mounting bolt from intake splined shaft; left hand thread (T30 torx bit socket 1/4″ / 1/4″ ratchet & extension).
“
Attach soft vise jaw liners to vise jaws.
Open vise jaws as far as necessary to insert piston shaft.
Insert piston shaft into vise and let piston sit on vise jaw liners top surface.
Strongly tighten vise.
Note: Vise jaw liners are soft and will not damage piston surfaces.
Caution: Do not clamp on piston without use of soft (nylon) vise jaw liners. Other types of jaw liners, including aluminum and rubber coated aluminum, can damage piston.
Loosen (break seize) piston bolt/cap (24mm socket 1/2″ / 1/2″ impact wrench).
If available, set impact wrench power to lowest setting.
Engage impact wrench in reverse for 1 second intervals at a time until bolt/cap loosens (seize breaks).
Note: Do not press down on impact wrench. This will hinder bolt/cap removal.
Note: Piston will spin slightly in vise jaws. If piston excessively spins, further tighten vise jaws.
Once piston bolt/cap loosens (seize breaks), loosen vise jaws to release pressure on piston.
Remove piston bearing bolt/cap (hand).
Remove bearing top washer (magnet pickup).
Note: Washer is often bound to bolt/cap with oil and comes off with bolt/cap.
Remove bearing top thrust (roller) bearing (magnet pickup).
Remove bearing center washer (magnet pickup).
Erase the lower thrust (roller) bearing using a magnetic pickup tool.
Unitech the bearing outer ring.
Clean bearing ring while still mounted in piston (brake cleaner & towels).
Insert right and left index fingers into bearing ring. Press against ring inner right and left walls and wiggle and pull ring out of piston.
If the ring is stuck, use a pick tip to pry it loose. Position the pick tip between the ring’s inner bottom edge and the bottom washer, then pry to break any seizing between the ring and washer (using a 90-degree pick).
Note: If bearing ring difficult to remove, loosen vise jaws.
Set aside bearing ring as it will not be reinstalled.
Remove bearing bottom washer.
Place pick tip between washer inner bottom and piston and pry washer out (90 degree pick).
Note: Washer is difficult to perceive until removed.
Cleaning of parts
Clean bearing parts (brake cleaner & towels).
Note: It is important bearing parts are thoroughly cleaned. This is needed to properly assess new bearing axial fit.
Clean piston bearing cavity and bolt/cap (brake cleaner & towels).
Installation of piston bearing
Bearing parts installation sequence from right to left.
Bearing parts from left to right: Bolt/cap, top washer, top thrust bearing, center washer, bottom thrust bearing, ring, bottom washer.
Insert bearing bottom washer in piston (fingers).
Note: Piston bearing top and bottom washers are interchangeable. Also washer faces are same thus washer can be inserted in either orientation.
Manipulate washer side to side while slightly pressing down to fully insert (fingers).
Insert new bearing ring in piston (fingers).
Note: New ring is marked “BS” on outer perimeter.
Initially insert ring in piston.
Insert right and left index fingers into ring. Press fingers against ring inner right and left walls and manipulate ring side to side while slightly pressing down to facilitate ring full insertion.
Note: If bearing ring difficult to install, loosen vise jaws.
Rotate position of fingers 90 degrees and repeat ring insertion to verify full insertion.
Note: Ring should fully mate with bearing washer (picture).
Insert bearing bottom thrust (roller) bearing in piston bearing ring.
Note: Piston bearing top and bottom thrust bearings are interchangeable. Also thrust bearing faces are functionally same thus thrust bearing can be inserted in either orientation.
Insert bearing center washer in piston bearing ring.
Note: Center washer faces are same thus washer can be inserted in either orientation.
Insert bearing top thrust (roller) bearing in piston bearing ring.
Note: Thrust bearing faces are functionally same thus thrust bearing can be inserted in either orientation.
Insert bearing top washer on top of piston bearing ring.
Note: Washer faces are same thus washer can be inserted in either orientation.
Manipulate washer side to side while slightly pressing down to fully insert (fingers).
Install piston bolt/cap (hand).
Hand tighten bolt/cap.
Strongly tighten vise onto piston shaft.
Note: Vise jaw liners are soft and will not damage piston surfaces.
Fully tighten piston bearing bolt/cap (24mm impact socket 1/2″ / 1/2″ torque wrench).
If available, set impact wrench power to lowest setting.
Engage impact wrench in forward for 1 second interval 3 times to fully tighten bolt/cap.
Note: Do not press down on impact wrench. This will hinder holt/cap tightening.
Note: Piston will spin slightly in vise jaws. If piston excessively spins, further tighten vise jaws.
Loosen vise jaws and remove piston from vise.
Inspection and adjustment of piston bearing
Install piston onto engine intake splined shaft with piston mounting bolt; left hand thread (T30 torx bit socket 1/4″ / 1/4″ ratchet & extension).
Lightly tighten.
Inspect piston bearing axial play.
Rotate piston to note resistance to rotation.
Hold splined shaft and tilt (rock) piston to each side to note bearing axial play (free space).
Note: Axial fit cannot be properly assessed until piston bolt/cap is fully tightened.
Note: Radial play, side to side movement, is normal and necessary. This should not be confused with axial play, in/out movement.
If piston binds and cannot be rotated then axial fit it too tight and loosening adjustment is needed.
If piston has any tilt movement then axial play is present and tightening adjustment is needed.
Any level of resistance (pre-load) in piston rotation indicates no axial play and is considered an optimal fit.
Note: US 3-series E46 ZHP performance package cars and cars with aftermarket performance cams (Schrick) must have no bearing axial play and bearing should have resistance to rotation (pre-load) to achieve optimal results.
Remove piston and piston mounting bolt from intake splined shaft; left hand thread (T30 torx bit socket 1/4″ / 1/4″ ratchet & extension).
Bearing loosening adjustment.
If splined shaft binds and cannot be rotated then axial fit it too tight and loosening adjustment is needed.
Disassemble piston bearing per above procedure.
Place sandpaper (~400 grade) on flat table top. Place bearing center washer on sandpaper.
Slide washer side to side on sandpaper ~6″ back and forth while moderately pressing washer on sandpaper. Perform sanding for 10 seconds.
Rotate washer 90 degrees and repeat sanding process.
Flip washer to opposite side and repeat above sanding procedure; 10 seconds sanding, rotate 90 degrees, 10 seconds sanding.
Clean washer (brake cleaner & towels).
Reassemble piston bearing per above procedure and reassess bearing axial fit.
Note: Washer is made from hardened steel and does not easily wear. Sanding procedure will remove ~.005mm washer height. Washer might need max .015mm height adjustment.
Bearing tightening adjustment.
If splined shaft has any tilt movement then axial play is present and tightening adjustment is needed.
Disassemble piston bearing per above procedure.
Place sandpaper (~400 grade) on flat table top. Place bearing ring on sandpaper.
Slide ring side to side on sandpaper ~6″ back and forth while moderately pressing ring on sandpaper. Perform sanding for 10 seconds.
Rotate ring 90 degrees and repeat sanding process.
Flip ring to opposite side and repeat above sanding procedure; 10 seconds sanding, rotate 90 degrees, 10 seconds sanding.
Clean ring (brake cleaner & towels).
Reassemble piston bearing per above procedure and reassess bearing axial fit.
Note: Ring is made from hardened steel and does not easily wear. Sanding procedure will remove ~.005mm ring height. Ring might need max .015mm height adjustment.
Once piston bearing fit is assessed and adjustment is performed if needed, spray oil into bearing from both ends of piston/bearing (oil spray).
Rotate bearing to distribute oil (finger).
Repeat procedure for second piston.
© 2025 Beisan Systems LLC