Pelican Technical Article: BMW Camshaft Timing and Vanos Unit Installation

	This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.
	This technical article is designed to be used in conjunction with other ones in our Technical Library. If you replace your head gasket, you will need to retime your camshafts and re-install the Vanos unit. For the purpose of instruction here, we'll assume that you have your cylinder head installed on the engine block, the crankshaft is locked at Top Dead Center (TDC), and your two camshafts are locked using the BMW camshaft locking tool. This article will guide you through the process of retiming your camshafts, and re-installing the Vanos variable camshaft timing unit. This article departs from our normal format of text and words mingled together. Since there are so many photos associated with this article, I have arranged them in assembly order with captions for each. Read through each caption as a step in the assembly process.
Figure 1	We start the procedure by making sure that the engine is at Top Dead Center (TDC). At this point, the TDC pin is installed into the locking position, and is holding the flywheel steady (see Head Gasket Replacement article for more details). The camshafts are locked in place using the camshaft locking tool. This will allow us to properly align and time the camshafts and the Vanos unit.
Figure 2	Shown here is the sprocket for the exhaust camshaft. Prior to mounting it on your engine, verify that the teeth of the gear are not worn or damaged. Also inspect the inner mounting slots to see if there is any wear from being loose at one time.
Figure 3	Install the sprocket onto the exhaust camshaft. Make sure that the mounting holes located on the camshaft flange are visible through the slots in the sprocket, and also make sure that the holes are biased towards the left side of the slots, as is shown by the red arrow. It may require some maneuvering to get the sprocket into it's proper position. Normally, it takes multiple attempts to get it to look exactly like the photo on the left.
Figure 4	Turn your attention now to the lower chain tensioner, which is located on the lower part of the block, on the right side of the car. We will be removing this tensioner and replacing it with a tensioner tool, which will keep the chain tight while we time the cams.
Figure 5	Here is the tensioner tool, which we use in place of the spring-loaded tensioner when timing the camshafts. It's important to use this tool, and not to rely solely on the spring-loaded tensioner - it does not provide enough tension when the car is sitting to accurate time the camshafts. Use the tool, and get the accurate reading that your engine deserves.
Figure 6	Remove the tensioner by placing a socket on the end piece of the tensioner. Do not remove the tensioner block which is attached to the housing (not necessary). When the tensioner comes out, it is spring loaded, so be prepared for it to pop out when you release the tension with your socket and driver.
Figure 7	Here is the tensioner assembly when you remove it. The assembly consists of a plunger, spring, cap, and sealing ring.
Figure 8	Replace the tensioner with the proper tensioning tool. For now, simply tighten the tool so that it is hand tight - we don't need or want the chain tension to be super-tight right now.
Figure 9	With the left sprocket installed, install the center plastic chain guide and torque down the long bolts that hold it in place. Don't over torque (10 Nm) - the first time I did this, the long bolt was brittle and broke off in the cylinder head. I had to take the assembly back apart, fish out the bolt, and then special order a new one (3 days wait).
Figure 10	With the guide in place, reinstall the top chain tensioner. These tensioners sometimes fail, but there really isn't a good method for testing them. I recommend replacement if your engine has at least 80,000 miles on it or so. A little bit of preventative maintenance can go a long way here. Tighten the bolts down to 20 Nm.
Figure 11	This photo shows the tensioner installed and ready to go. Inspect the ramp before you install it to see if there is any significant wear or obvious deformations. The ramp should still be held in place using the two small hex keys that you inserted when you removed it. Do not release the tensioner yet.
Figure 12	Place the camshaft sensor cap onto the intake camshaft. This metal cap serves to trigger the camshaft position sensor, and lets the engine know whether the engine is on an intake or exhaust stroke of it's 4-cycle process. The camshaft position sensor fits into the hole on the right side of this photo (you can make out the small green o-ring to the lower right).
Figure 13	Shown here are the studs for the thrust washer and sprocket. These studs look very similar to the ones that mount the valve cover to the head - don't mix them up. Compare yours carefully to the ones in the photo to make sure that you have the right studs. It is also important to keep in mind that there are two types of Vanos units (early/late). The early units do not have a plate spring, whereas the later ones do. The plate spring fits over the intake camshaft thrust washer, and requires slightly longer studs. This particular car does not have the spring plate.
Figure 14	Install the thrust washer onto the intake camshaft. Use the special studs, and install it in the same configuration in which it was removed. In other words, in this photo, you can see the oil stain from the slots that surround the studs. Install this side facing you when you reinstall this thrust washer (copy the photo). Torque the studs to 20 Nm.
Figure 15	Now, take the two intake sprockets and chain and attach it to the assembly. See the photo for the proper orientation of the two sprockets. The exhaust sprocket should have it's cup facing outwards, and the intake sprocket should have its cup facing inwards. Verify that both sprockets are correctly mounted flush to the surfaces behind them. The intake sprocket is installed with the flat side facing you (the Vanos unit). The collar of the intake sprocket faces and points to the camshaft. Align the two sprockets and the chain so that the slots are centered on both sprockets (see arrows).
Figure 16	Here's another view of the intake Vanos sprocket, correctly mounted flush against the thrust washer behind it. Soak all of the sprockets, gears and chains in clean motor oil before you install them - these are sliding parts that need lubrication.
Figure 17	Now, install the thrust washer onto the intake camshaft and tighten the nuts down. It's okay to reuse the old nuts. If you have the Vanos unit with a spring plate, then install it first, before the thrust washer (not shown). Tighten the nuts down to 10Nm. IMPORTANT: With the nuts tight, the inside sprocket should be free to rotate back and forth about 20 degrees, along with the chain. When I assembled this engine, I found that it could not. Some of the bolts and flanges were worn, and I had to order new ones. The Vanos unit requires that this "sandwich" of parts be able to rotate smoothly. Verify this prior to proceding.
Figure 18	Install the screws onto the exhaust camshaft. Place them onto the sprocket and tighten them only HAND TIGHT. We will be making adjustments later on, and these bolts only need to be in place to hold the exhaust camshaft in its proper position.
	NOTE: From this point on, these are the instructions that you will want to look at if you are simply replacing the Vanos unit.
Figure 20	Here is what your engine should look like now. You have the new camshafts installed, you have the chain and sprockets properly setup, and we're ready to install the Vanos unit.
Figure 21	Shown here is the Vanos unit. It consists of a solenoid, and a hydraulic gear that is activated when oil pressure is released into the unit by the solenoid. It's a rather simple device. The gear on the unit is pushed out by oil pressure and as it moves outward, it rotates the small sliding camshafts sprockets, thus advancing the camshaft timing.
Figure 22	Test the Vanos unit by pulling out the gear plunger all the way. You should be able to simply pull on it with your hand, and it should extend from the housing (see arrow). If the unit still has oil in it at this time, it will make a gurgling noise or two. Push the plunger back into the unit when you are finished.
Figure 23	The BMW service manuals recommend that you place some silicone sealant around the left and right mounting points (alignment pins) for the front Vanos seal. This photo shows the right side (looking at the engine from the front). Repeat for the left side alignment pin.
Figure 24	Install a new seal onto the front of the cylinder head (indicated by the arrow). The seal should be made of a thin metal.
Figure 25	Now comes the tricky part. Rotate the front sprocket/chain assembly all the way clockwise to the right (towards where the air cleaner sits). With the plunger of the Vanos unit pushed all the way back into its housing (important), place the Vanos unit on the cylinder head.
Figure 26	The Vanos unit has inside gears that need to mesh with the ones on the sprocket (see arrow). When you push the Vanos unit onto the cylinder head, it will not want to easily mesh with the gears on the sprocket. Important: the sprocket/chain assembly should still be rotated as far clockwise as possible.
Figure 27	With your fingers, rotate the spline shaft on the Vanos unit, until you can engage one spline of the sprocket. Pushing forward on the Vanos unit, carefully rotate the sprocket/chain assembly counter-clockwise. As you do this, the Vanos unit should slide in towards the cylinder head. Always ensure that the FIRST suitable tooth combination between the sprocket and the Vanos unit engages.
Figure 28	Reinstall the main mounting bolt and the engine lift ring.
Figure 29	After tightening down the Vanos housing, and clean up any squeeze-out from the silicone that you used to help seal the unit to the cylinder head.
Figure 19	With the sprockets properly installed, now pull out the retaining pins and reapply tension to the chain. The tensioner should spring back with some force and tight the chain quickly. If it appears sluggish, or does not spring back, then replace the tensioner before continuing.
Figure 32	Now, tighten down the tensioner tool to 1.3 Nm. This is such an incredibly small amount, that you can simply use a hand-wheel ratchet to tighten the chain very tight. You want to remove all slack in the chain prior to tightening down the exhaust sprocket. Use of the regular spring-loaded tensioner does not place enough tension on the chain to correctly tighten the sprocket.
Figure 30	With the tensioner tool still in place, tighten down the four nuts on the exhaust sprocket (15 Nm). Reinstall the plugs on the outside of the Vanos cover.
Figure 34	Remove your tensioner tool, and replace it with the real tensioner. Make sure that the slot in the end of the tensioner is correctly aligned with the ramp on the inside of the engine. If you make this mistake, it will cause the chain to rattle fiercely and may cause damage to your engine.
Figure 35	Remove the camshaft holding tool from the rear of the engine. Also remove the flywheel locking tool.
Figure 36	You're finished! Your Vanos unit should be installed, the camshafts will be timed properly, and all you have left to do is: Connect Vanos oil line Connect Vanos electrical control line Install valve cover with new seal Reinstall Coils
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