Most modern diesel vehicles are fitted with damping type crankshaft pulleys that reduce harmonic noise and vibration from the crankshaft to the rest of the driveline components. The VW Crafter CR35 is no exception, it has a sandwich type of pulley bonded with a metalastic rubberised material that isolates the inner section from the outer belt drive section. Over time what happens is the rubber deteriorates and the flex within the pulley increases causing the two halves to touch creating a clacking sound.
As the pulley begins to fail in the early stages you may only begin to here a randomised tapping when the engine is running. Usually this not heard when the vehicle is cold and the rubber sandwich is harder, as it warms the rubber becomes more pliable and flexes – allowing the two halves to touch and create a tapping noise.
To the uneducated ear this noise can be very misleading. Its sound is not localised as you would imagine to the pulley and the vibration seems to spread and appear if it is emanating from another component on the auxiliary drive belt path. Common mistaken components are power steering pump, alternator and idler assembly, in some cases it even sounds convincingly like piston-slap or little end wear, even camshaft problems – sounding just like a sticking tappet! So as you can see, when the pulley first starts to fail it is very difficult to identify without close inspection off the vehicle.
As time passes the damped pulley begins to pull away from the rubberised composition and the flex in the assembly begins to allow greater rotational movement between the two parts of the pulley. There are two machined outer slots on the face of the pulley that have sliding mushroom pins tapped into the inner mass of the assembly. These begin to touch the end of the slide and make a very distinctive racket – sounding like a ‘Brrrap tap’ noise when the auxillary belt path is loaded, such as when turning the powered steering at slower speeds, or blipping the throttle.
In addition to obvious cracking and parting of the rubber bonding, if you suspect the pulley as being your problem, prise off the two plastic banana shaped covers from its front face and see if you can see any wearing of the pin and slot components signifying that the parts are coming into contact with each other or touching – this is not normal!
Replacement of this component can be costly through a main dealer but can be carried out with a minimum of tools, if you have the time to work around the need for special lock tools that are needed to fix the crankshaft while the centre bolt is undone and tightened. I would recommend the good quality Corteco kit available from Euro Car Parts for about £120. There are cheaper parts available (£85-ish) but this Corteco kit is excellent quality and comes with new bolts and shim, everything you need to complete the job.
It is important that you have good access above and below the van to carry out this job and the best way to do this is to raise the front of the vehicle onto ramps. It is better to jack the vehicle, a side at a time and place the ramps underneath the wheels, then you can oppose each ramp so it locks the axle from movement against the ramps end stop. Raise the bonnet and remove the air box, detaching the red electrical point by pushing in the clip at its base and sliding upward. Remove the wiring plugs from the pressure sensor and air flow sensor. Place the airbox out of the work area. Now unclip the power steering reserve from its slide and fold it back on its pipes to lie on top of the engine. Now take off the radiator top blind that covers the gap between the matrix and the fan cowling.
Unclip all the small cooling system pipes attached to the fan cowling, pulling upward on the cowl to release the clips either side. Once released, push the cowl back towards the engine to gain restricted access to the viscous fan unit. Using a 10mm hexagon key while locking the fan pulley with a slim bar undo the centre fixing of the viscous fan and remove it from the vehicle. Now pull up the complete fan cowling, manoeuvring it around the radiator tank pipes on each side, lifting it up and clear of the engine compartment.
Using a broad flat bar or pry, relax the tension on the auxiliary belt tensioner enough to slip the belt off the power steering pulley. Remove the drive belt completely.
From under the vehicle remove the two banana inspection caps from the face of the pulley. Select a 27mm hexagon socket and breaker bar of suitable length (the centre bolt is tightened to 160Nm +180 degrees ! as specified in the kit) so expect it to be tight. You will need the aid of an assistant for this part – Using a stout steel bar and suitable blocks of wood, wedge/place the end of the bar onto the protruding mushroom pin within the slot of the pulley. If undoing – align the pulley by rotating the engine so the bar wedge you are creating is at the 9 o’clock position, if tightening, the 3 o’clock position. It is important to maintain the bar at 90 degrees to the pulley and vertically down. While your assistant holds things in place, from the top use your 27mm socket and breaker to release the nut. There is of course a special locking tool that you can purchase that sits inside the centre of the crank pulley allowing it to be locked in position. You may wish to purchase one, but unless you are lucky, this may present some difficulty as usually this tool forms part of a locking kit and is quite expensive.
Once the large centre bolt is removed you can remove the remaining four bolts that hold the crank pulley to the internal cam belt pulley face. Once these are removed you can wiggle the pulley from the end of the crankshaft. Once removed, extract the shim washer from the centre of the crankshaft end. Ensure you fit the new one supplied in your kit. Fit the new pulley observing correct orientation of the locator peg and hole in the pulley rear face. Finger tighten the four smaller bolts into the pulley and using the same technique as was used on removal, tighten the centre bolt. Once you are happy with this, rebuild the remainder of the engine components in the reverse order of disassembly.
More information on the Crafter CR35 timing belt change here: