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924 Cam Belt Replacement

Disclaimer: any information provided here is used at your own risk. I accept no responsibility for any damage you may do to yourself, others or you car. Having said that I thoroughly recommend getting yourself the Haynes owners workshop manual for the 924. It's the best publication of it's type for the car, oh and also make sure you're on friendly terms with your local porsche parts interpreter and wrecker, they can save you both time and money with their useful information.

Changing the timing belt
How old is your timing belt? Don't know? Then replace it NOW! Changing the belt is easy and unlike the 944 you don't need any expensive tensioning tool.
1) remove the timing belt guard-3 bolts 2 at the top and one in the centre at the bottom.
2) remove any drive belts (ie. alternator, power steer etc)
3) rotate the engine to No.1 TDC using the timing mark on the flywheel [See Right] (the mark varies for US and euro engines so check which one you need!) and the mark on the back of the top cam drive pulley (it lines up with a pointer on the cam cover) [See Left]
4) using a large spanner and a socket wrench, loosen the small bolthead on the tensioning pulley (mounted on the water pump) and gently rotate the pulley (with the large spanner) to release the tension from the belt.
5) the belt can now be removed.
6) replace the belt making sure it meshes properly with the pulley's the bottom pulley can be a bit tricky to see a torch will help.
7) Again using your large spanner turn the tensioning pulley until the belt is quite tight.
8) Check the tension by twisting the long side of the belt with your fingers through 90 degrees. You should just be able to twist it that far.
9) using your socket wrench tighten the retaining belt.
10) check that the engine is still at TDC. Using the mark on the camshaft drive pulley and on the crankshaft. Sometimes you can move the timing while tensioning the belt. I usually rotate the engine through a full revolution by hand then re-check the timing marks to make sure everything is OK.
11) replace your accessory drive belts and tension them (now is a good time to fit new ones!)
12) replace your cam belt cover (you can leave this till last in case you make a mistake!)
13) start her up (if you like you can check you ignition timing with a strobe although if you didn't muck anything up you won't need to) if you mucked up the timing marks then either i) the engine won't start or ii) it will run really rough or ping like crazy (if you're one notch out). Re-align the engine to No1 TDC and recheck the timing marks again!

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