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Replacing Your Audi A4 Timing Belt
 
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Pelican Technical Article:

Replacing Your Audi A4 Timing Belt

Steve Vernon

Time:

3 hours3 hrs

Tab:

$30

Talent:

***

Tools:

10mm socket, 19mm 12point, 6mm, 8mm Allen socket, flathead and Philips screwdriver

Applicable Models:

Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06)

Parts Required:

New timing belt

Hot Tip:

Patience

Performance Gain:

Won't leave you stranded at the side of the road

Complementary Modification:

New timing belt

The connection between the crankshaft and the camshafts in the Audi A4 1.8-liter is a single rubber belt. This belt rides on sprockets on both the crankshaft and camshaft. The belt will stretch over time and eventually fail, which is not a good thing since the 1.8-liter engine is what is referred to as a contact engine or interference engine. This means, if the belt stretches enough to skip a tooth or fails, the tight clearance tolerances between the valves and pistons will be lost and the pistons can make contact with the valves. This is VERY bad and at the very least will result in a valve job, if not the destruction of the engine. This is why changing the timing belt is one area of maintenance that should never be skipped or stretched out. Always replace the belt according to the vehicle's maintenance schedule.

Audi recommends changing your timing belt every 100,000 miles. While you have the belt off, you should really consider changing out the tensioner as well. Even if the tensioner is not giving you trouble, there is a tremendous amount of work to get to this point. Replacing the tensioner may just be cheap insurance. Please see our article on timing belt tensioner replacement. The timing belt connects the engine's crankshaft with the camshaft. While there are very specific procedures you need to perform to eliminate the possibility of damaging the engine, it is still a viable and doable DIY project. Note: if you do not follow the specific details and line up the crank to cam sprockets correctly, you can do terminal damage to the engine. So, just take your time and double check everything as you go.

To perform this job you will need to first move the lock carrier to the service position and then remove the accessory belt and tensioner. Please see our article on these procedures for additional assistance. Note: the front of the vehicle has been removed for photographic purposes; you do NOT need to remove the rfont to perform this work.

There are two covers on the front of the motor protecting the timing belt; the upper (red arrow) and the lower (yellow arrow).
Figure 1

There are two covers on the front of the motor protecting the timing belt; the upper (red arrow) and the lower (yellow arrow).

There are two lines connected to the top of the upper valve cover, a coolant line from the turbo (red arrow) and a vacuum line (yellow arrow).
Figure 2

There are two lines connected to the top of the upper valve cover, a coolant line from the turbo (red arrow) and a vacuum line (yellow arrow). You do not need to disconnect these lines to remove the cover. Just unclip them from their holders. Note: I removed them for photographic purposes.

There are two clips holding the upper cover to the head (red arrows); unclip them and pull the cover up and away from the front of the motor.
Figure 3

There are two clips holding the upper cover to the head (red arrows); unclip them and pull the cover up and away from the front of the motor.

You can now remove the upper cover (red arrow).
Figure 4

You can now remove the upper cover (red arrow).

The lower cover contains the witness mark for lining the crankshaft up at Top Dead Center or TDC (yellow arrow).
Figure 5

The lower cover contains the witness mark for lining the crankshaft up at Top Dead Center or TDC (yellow arrow). Before removing the cover and vibration dampener, use a 12-point 16mm socket and turn the crank bolt (red arrow) clockwise until the mark on the dampener is lined up with the witness mark in the cover.

Make sure that the motor is at TDC for the number one cylinder.
Figure 6

Make sure that the motor is at TDC for the number one cylinder. Check that the witness mark on the head (yellow arrow) lines up with the witness mark on the cam sprocket (red arrow). If they do not line up, rotate the engine until they do. Note: as the belt stretches, the witness mark may be off up to one-half of a tooth on the sprocket but no more.

Hold the crankshaft bolt in place with a 12-point 16mm socket (red arrow).
Figure 7

Hold the crankshaft bolt in place with a 12-point 16mm socket (red arrow). Use a 6mm Allen to remove the four dampener bolts (yellow arrow).

Remove the dampener.
Figure 8

Remove the dampener. You may have to give it a few taps with a rubber mallet, but never hit it with a metal hammer. The dampener has a locating hole (red arrow) that corresponds with a nipple in the crank (yellow arrow); this insures that the dampener can only be installed one way, ensuring proper alignment with the TDC markings.

Use a 19mm socket and remove the five 10mm bolts holding the lower timing cover in place.
Figure 9

Use a 19mm socket and remove the five 10mm bolts holding the lower timing cover in place.

Mark the block (green arrow) and the crank sprocket (red arrow) while the motor is confirmed at TDC, this will save you from having to reinstall the cover and dampener when confirming everything is lined up at TDC for installation of the new belt.
Figure 10

Mark the block (green arrow) and the crank sprocket (red arrow) while the motor is confirmed at TDC, this will save you from having to reinstall the cover and dampener when confirming everything is lined up at TDC for installation of the new belt.

You will need to compress the piston (green arrow) in the tensioner until there is no gap in between the mount and tensioner (red arrows).
Figure 11

You will need to compress the piston (green arrow) in the tensioner until there is no gap in between the mount and tensioner (red arrows).

While holding the tensioner in place with an 8mm Allen (red arrow), use a 13mm socket or wrench and loosen the nut holding the tensioner in place (yellow arrow).
Figure 12

While holding the tensioner in place with an 8mm Allen (red arrow), use a 13mm socket or wrench and loosen the nut holding the tensioner in place (yellow arrow).

With the 13mm nut loose, you will need to turn the tensioner counter clockwise until the piston is compressed and the gap is gone (red arrow).
Figure 13

With the 13mm nut loose, you will need to turn the tensioner counter clockwise until the piston is compressed and the gap is gone (red arrow). The piston is hydraulic and can only be compressed slowly. Take your time and do not expect to quickly force the piston down. If you have the locking tab for the tensioner, you can install it to keep the tensioner locked in the open position. If you do not, you can let the piston expand and recompress it when reinstalling the new belt.

You can now slip the belt off (red arrow).
Figure 14

You can now slip the belt off (red arrow). I find it easiest to remove the belt first from the water pump.

If you are installing the belt and do not have the locking tab, you will need to slowly recompress the piston in the tensioner (yellow arrow).
Figure 15

If you are installing the belt and do not have the locking tab, you will need to slowly recompress the piston in the tensioner (yellow arrow). Install the belt, making sure that the crank and cam sprockets remain on TDC. If one of the sprockets should turn while installing the belt, remove the belt, reset the sprocket to TDC and start over (red arrows).

You will now need to set the proper tension on the tensioner.
Figure 16

You will now need to set the proper tension on the tensioner. There needs to be a gap between the tensioner and tab of 6-10mm. You should set yours at 8mm by using a drill bit to slip between the measuring places (yellow arrows) If the piston is compressed you can use a set of needle nose pliers or circlip tool to set the distance using the adjuster on the wheel (red arrows). Once the gap is set, tighten down the 13mm nut (green arrow). Rotate the engine a few cycles by the crank bolt and recheck the clearance (yellow arrows). If the clearance is more than desired, loosen the 13mm nut and use your 8mm Allen to recompress the piston to the desired gap. If it is less, you can loosen the nut and use your needle nose pliers to add gap and then retighten the nut. Make sure you rotate the engine a few times and check the gap. Also be sure that the belt is aligned properly before putting everything back on the motor.

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