Volkswagen Passat or VW Jetta TDI chirping in cold weather and cold start- how to solve

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Introduction

If your 1996 1997 b4 Passat or 1996-1999 a3 Jetta has developed a chirping sound on cold starts in cold weather but goes away once the car warms up, a few things may be happening.

First check the following:

  1. If you hear a rubbing sound, first check the timing belt by unclipping the timing belt cover and looking for damage to the timing belt.
  2. Alternator bearings and pulley, power steering pulley, air conditioner clutch could be bad and creating noise.
  3. The Jetta has a one way clutch on the alternator pulley which can wear out and create noise, the Passat does not.  To inspect, remove the belt and use a wood dowel or chopstick to hold the fan inside the alternator.  The pulley should only rotate freely one way.
  4. Accessory belt tension - as a rough rule of thumb to measure tension, push the belt at the midpoint by hand, it should deflect about 1/4"-1/2".  
    Warning: a tighter belt is not better because excess tension will wear bearings and pulleys.
  5. The accessory/serpentine belt on the TDI is automatically tensioned by a lever and spring.
  6. Oil, grease, or other fluids dripping onto the belts causing belt slip.
  7. You can check the serpentine (accessory) belt tensioner pulley, clean and lube as outlined here.
  8. I would just replace them with the harmonic balancer as described below since it's probably the cause - replacing the tensioner might only temporarily fix the problem.

If these are okay, your car's harmonic balancer pulley and serpentine pulley tensioner spring may be worn out.  Replacing both of these will normally solve the chirping noise.  Worst case you just have to replace the lever and rod.  Summary of procedure: remove the belts and put on a new pulley and tensioning spring.  Grease the old tensioning lever or put in a new one.  Detailed steps below.

The noise is caused by inconsistent belt tension in cold temperatures.  The redesigned replacement harmonic balancer pulley should help reduce this tendency.  A large source of the drag that causes the noise comes from the alternator.  When you start the car, the alternator generates more load to recharge the drain of the battery from starting the engine and the glow plugs.  The cold temperatures may also cause the belts and the rubber parts of the pulley to contract and loosen.  Once the engine warms up the noise goes away.  If the engine doesn't make this noise once it's warmed up then this is most likely the source of the noise.

As a test and temporary way to reduce the likelihood of chirping, also disable the daytime running lights and reduce the electrical load.  Turning off the DRL will reduce the load on the alternator until the car is warmed up.  Also turn off the radio, cabin vent fan, or any other electrical load as a test.  Once the car is warmed up, turn the headlights back on for safety.  For specifics on turning off the DRL, refer to : 1000q: passat - disable DRL.  If the chirping is less or shorter, a worn crankshaft pulley is likely.

Here is a picture comparing the old VW part #028 105 243 k and the new VW part #028 105 243 t harmonic balancer/dampener pulley/crankshaft pulley.  The old pulley consists of an inner pulley and outer pulley with a rubber ring in the middle.  When cold, the pulley contracts and slips, causing noise.  The new pulley is one piece with the rubber built into the ring.  The drilled dimple on the new pulley is for balancing.

Parts (click links to compare current prices)

Harmonic balancer/dampener pulley #028 105 243T, from AutohauzAZ, part #028105243T 
Serpentine belt (alternator) spring tensioner #028 903 315 R
new belts
4 allen bolts for the harmonic balancer (6mm) VW # N 903 487 04 (optional but suggested since they will probably be damaged during removal) (clicking on link gives n903487-06, it's possible part has been superceded)
Relay roller #028 145 278 E (optional, it's the plastic pulley)
Protective Cap #028 145 291 A (optional)
Tensioning Lever #028 903 308 G (optional but not suggested)
Tensioning lever dust cap #028 903 310 (optional x2 pieces)

13mm socket
16mm socket
6mm and 5mm allen wrench/socket
T-25 torx screwdriver
PB Blaster (strongly suggested)
High temp moly or all purpose auto grease
EZ out stripped allen bolt remover (optional)

Procedure to quiet the TDI cold chirping

Jack up the front of the car, chock the rear wheels, put the car in gear, set the parking brake on, set the car securely on jack stands on stable, solid, and level ground.  Make sure the car is secure before doing anything else.  Always wear eye protection, follow the precautions in the factory service manual, see the TOS for the full legal disclaimer.  Use a service cover or some towels taped to the fender to avoid paint damage from watches or belt buckles.  I use wood blocks to support the car at the wheels.  See 1000q: wood block for more details on these.

Remove the plastic splash shield (T-25 torx and a few screws or bolts).

Spray a little PB Blaster on the 4x 6mm allen bolts on the harmonic balancer pulley.  They tend to get stuck and the PB blaster needs time to work.

Remove the power steering/water pump v-belt (outer belt) by loosening the 3 red circled bolts (2 x 13mm), (1 x 16mm).  You can then swing the power steering bracket/pump a little to remove the v-belt.

Remove the serpentine belt by relieving the tension off the belt.  You can use a wrench on the tensioning lever arm to move it while you slip off the belt.  Keep your fingers clear of the belt and lever in case it slips!  Although the service manual says to use the idler pulley's bolt, I don't do this because it can strip the bolt.  I avoid using a screwdriver on the lever since it can damage the plastic pulley.  Then remove the tensioner spring (2 x 6mm allen bolts), (1 x 5mm allen bolt) marked by the 3 red circles below.

Here is another view of the lever and tensioner with the injection pump and bracket removed.

Remove the tensioner spring.  It's pressed onto the end of the lever so I suggest using a lever to pry the end with the idler pulley to the pass side.  This will pop the tensioner spring off (pictured at about life size below).  Make sure the center allen bolt is removed.

Remove the allen bolts on the harmonic balancer pulley (4 x 6mm).  The bolts can be soft and tend to strip so you may want to get replacements ahead of time.  I don't suggest using the center 19mm 12 point bolt to counterhold the allen bolts because that bolt is attached to the crank.  It's a 1 use only stretch bolt and although later TDI can use it for counterholding, this bolt uses a lower torque spec along with a different crank and bolt.  To counterhold the 4 allen bolts, I suggest putting the car in gear and having a helper step on the brakes as the primary method of counterholding.  As long as the tires are on ramps/wood blocks, the brakes will hold tight.  Concentrating on 1 tool is also easier than using 2 tools at the same time in a limited space.  If the car is lifted and the tires are in the air, use the 19mm 12 point bolt as another method of counterholding.

Suggested: spray the allen bolt heads with PB Blaster and let them soak to help loosen them.  Pictured below are the belts and the pulley removed.  While you are here, inspect the condition of the pulleys and other belts for oil or water leaks.  The 4 allen bolts will probably be hard to remove, I suggest having an EZ out (pictured at top) handy incase the allen heads get stripped.  When using an EZ out, press on the bolt head and make sure it's sharp.  If you let it slip it won't bite into the bolt head and it will dull.

Installation is the reverse of removal.  Note: because of 1 offset hole, the harmonic balancer bolt holes will only line up 1 way!  I also suggest pulling back the tensioning lever boots and greasing the lever while moving it in and out, up and down.  If you want to replace the lever, see the steps below.  You may want to use a tiny touch of anti-seize on the 6mm allen bolts for the harmonic balancer so they won't be stuck next time.   I believe the 6mm allen bolts come with threadlocker when new due to vibration so it's up to you whether to use any anti-seize.  However, I chose to use a tiny touch of anti-seize since the problem is more likely seized and stripped bolts and they were all tight when I removed them for the next service.  Also check the length of the new bolts against the length of the old bolts.

Optional: Remove the tensioner rod by removing the airbox.  This is what mine looked like.  The advantage of removal is that you can grease the whole rod.  If you do, inspect the bushings for damage.  It's possible that squeaking is also from worn bushings.  Although VW does not list the bushings in the part catalog, they are available (listed as a part for the Eurovan) as VW# 028 903 313  (028903313).  A replacement lever is VW# 028 903 308 g (028903308g)

Here are some more pictures and tips from user "diesel?" and his experiences in this forum thread: http://www.myturbodiesel.com/forum/f4/96-passat-tdi-serpentine-tensioner-problems-6068/

Here is his worn lever and bushings with the new part.

A closeup of the wear on the other side:

Here is his worn bushing and the replacement.

If you remove the airbox, check for wires that have been rubbing through.  Clean the old grease off with brake cleaner or degreaser and regrease.  Keep the grease off the belt and pulley.

Put the new pulley on and reinstall the belts.  

Torque specs

Double check the torque of the four harmonic balancer bolts. (15 ft lbs).  The idler pulley bolt on the tensioner lever arm is also 15 ft lbs.

To tension the power steering v-belt, torque the splined tension adjuster (the bolt with the star spacer on it) to 2.9 ft-lbs for used v-belts, 5.1 ft lbs for new v-belts and then torque it's bolt to 18 ft-lbs.  The v-belt should have about 5mm of deflection in the middle.

Want to share your experience?  Cold squeaking from the belts on your Jetta or Passat TDI could be caused by a few things.  Please ask in the myturbodiesel.com forums