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Pelican Technical Article:

Timing Belt Replacement

Steve Vernon

Time:

4 hours4 hrs

Tab:

$15 to $120

Talent:

***

Tools:

24mm, 17mm, 10mm socket, flywheel lock, Porsche special tool 9201, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

Porsche 944 Turbo (1986-89)

Parts Required:

New belt

Hot Tip:

Make sure engine is at Top Dead Center (TDC)

Performance Gain:

Proper engine operation

Complementary Modification:

Replace balance shaft belt

Replacing the timing belt is an important part of the maintenance on your Porsche 944. Even if you do not need to replace it, the belt will need to come off to perform work; including changing the water pump project. If you are removing the belt and going to reinstall it, make sure to mark the direction of rotation.

You are going to need to safely raise and support the vehicle and remove the under engine tray. Please see our articles on "Safely Raising and Supporting Your Porsche 944" and "Removing the Under Engine Tray."

To replace the timing belt, you will first need to remove the balance shaft belt. Please see our article on "Balance Shaft Belt Replacement" first.

With the balance shaft belt removed, you are looking at the timing belt.
Figure 1

With the balance shaft belt removed, you are looking at the timing belt. In this photo, you can see the timing belt winding around the water pump (red arrow) the tensioner (yellow arrow), the idler (green arrow) and crank pulley (blue arrow). Note that the smooth side of the belt powers the water pump pulley. Because of this fact, getting tension correct is very important. Overtightening the tension on the belt will cause a whine from the pump due to the extra stress on the bearing. This will lead to premature pump failure.

Brace the tensioner with a 24mm wrench (red arrow) and remove the 17mm nut (yellow arrow).
Figure 2

Brace the tensioner with a 24mm wrench (red arrow) and remove the 17mm nut (yellow arrow). Failure to counter torque the tensioner will result in too much force on it, which can lead to diminished life expectancy of the tensioner.

Use a 17mm socket and remove the idler pulley (red arrow).
Figure 3

Use a 17mm socket and remove the idler pulley (red arrow).

Remove the two 10mm nuts holding the guide plate (red arrows).
Figure 4

Remove the two 10mm nuts holding the guide plate (red arrows).

Remove and inspect the guide plate (red arrow).
Figure 5

Remove and inspect the guide plate (red arrow). There should be no wear on the plate; if your belt has gotten too loose and made contact with the guide plate, you should replace it.

If you are planning on reinstalling the belt, remember that it is only ribbed on one side (yellow arrow).
Figure 6

If you are planning on reinstalling the belt, remember that it is only ribbed on one side (yellow arrow). Mark the direction of rotation and inspect the belt for fraying, cracks, dry rot or any other damage and replace as needed (red arrow). If you are unsure of the age of the belt, you should replace it.

When installing the belt, make sure that the engine is set at TDC and that the mark on the cam pulley (red arrow) lines up with the mark on the cam housing (yellow arrow).
Figure 7

When installing the belt, make sure that the engine is set at TDC and that the mark on the cam pulley (red arrow) lines up with the mark on the cam housing (yellow arrow). It is important that these do not move during installation or tensioning.

Set the tension on the belt until it is tight enough that you can twist the belt half way between the cam and crankshaft pulley (red arrow) 90 degrees with your thumb and forefinger.
Figure 8

Set the tension on the belt until it is tight enough that you can twist the belt half way between the cam and crankshaft pulley (red arrow) 90 degrees with your thumb and forefinger.

Once everything is tightened and you have checked for alignment of the sprockets, remove the flywheel lock and turn the engine two complete rotations.
Figure 9

Once everything is tightened and you have checked for alignment of the sprockets, remove the flywheel lock and turn the engine two complete rotations. Then check to make sure that the TDC and cam markings line up. Rotate the engine counter clockwise 10 degrees or one and a half teeth on the cam gear. Check the belt tension using Porsche special tool 9201. Pull the lock pin on the tool to release the tension roller. Align the drag needle with the gauge needle. Install the tool on the long section of the cam belt between the cam sprocket and the cam belt idler roller. Make sure that the tool's tensioning roller is on the toothed side of the belt. With the timing belt tool installed, the gauge on the tool will be upside down and the flat bars on the tool that slide between the timing belt and the timing belt cover will be a snug fit. Push the tensioning roller against the cam belt until the locking pin on the tool engages. The tension on a new belt should be 4.0 +/- 0.3. If you are reinstalling a used belt, it should be 2.7 +/- 0.3. Installation is the reverse of removal.



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