Check John's excellent site for the T-belt step-by-step procedure:
Since you are asking about timing belt issues, I worked up a revision to one of my earlier posts for you. See below:
Water Pump and Timing Belt Replacement Essentials:
You have to remove or loosen everything from the front of the engine including:
Fan and Throttle Linkage Console/Carrier
Power Steering Pump
Front Timing Belt Cover
Distributor Timing Belt Covers
Tensioner - Rebuild it
You can easily break off water pump bolts by over-torquing or removing stuck ones. It would be nice to have the engine cleaned first - without losing any original factory stickers. However, I would not drive the car for that after receiving a belt tension warning. I heartily recommend that you or your mechanic replace everything on this list while you are in there. Rollers have bearings that will become fowled by anti-freeze or mileage.
Buy the aftermarket belt tension tool for around $50, and the flywheel holding tool for around $20.
Socket for front main pulley Metric Allen Wrenches with 3/8" drive fit Breaker bar and cheater bar for pulley socket (not really special tools)
Metric deep sockets (not really special tools) Universal, ratchet, and extensions for sockets (not really special tools)
Tool, Part, & Manual Suppliers:
928 Specialists at 828-766-9280, Devek, and 928 International 800-634-6117.
Those "Big 3" can hook you up with about anything for the 928. Tweeks, Pelican, Automotion, etc. can also help with your needs. See the Rennlist site for contact information. The other tools are available from Sears, and most auto parts stores.
Join the free Rennlist 928 Web Board. The web interface is the most effective that I have used. The email groups give an additional audience, but less sophisticated interface. See: http://www.rennlist.org
New Parts & Supplies:
Water Pump - maybe Porsche rebuilt, not new Water Pump Gasket
All other Belts
Aluminum Safe Antifreeze
Distilled water (to be used with antifreeze)
Thermostat sealing ring
Radiator Hoses (2)
Timing Belt Idler bushings (2)
Radiator Drain Plug
Block Drain Plug O-rings - metal (2)
Boot or rubber end cover - looks like a hollow half doughnut
90 weight gear oil
Optional Parts & Supplies:
Front Seals: Main, Oil Pump
Clutch (pulley driven) Fan Bearings
Silicon Fan Clutch Fluid - from Toyota
Timing Belt Tension Check:
You will need the belt tension tool to check tension after approximately 1,500 miles and 10-15k mile intervals afterwards. Remove the passenger side timing belt cover (at the cam gear, remove distributor first), and check the tension. Timing belt and/or water pump failure is common after 60k miles on the 928. Take belt tension very seriously. That is the Achilles heel.
The Parts and Technical Reference Manual is a great source of diagrams, part numbers, etc. The factory manuals provide procedures that are very helpful. There are parts microfiches and CDs.
While you have the pulley driven fan off, you may want to replenish the silicon with Toyota supplied fan clutch fluid. You may also wish to replace the front main seal, and the oil pump seal while they are relatively exposed. Those seals are tough to change. May replace the Clutch Fan Bearings.
Detailed Procedure & Photo Links:
Greg Nichols' page has troubleshooting procedures for the timing belt light and more at:
Tony's page has pictures and procedures:
John Pirtle's site goes into great detail, with awesome pictures: