Definitions and Acronyms

• TDC: Top Dead Center. This is the position of the engine when the #1 piston is up as far as it will go.

Tools Required:

• 5mm, 6mm, 8mm, and 10mm allen wrench sockets (that go on your favorite ratchet ... regular allen wrenches won't do)
• 10"-12" socket extension
• Flexible socket extension
• 10mm 6-point deep hex socket (or shallow socket with a short extension)
• 24mm (or 15/16") 12-point socket
• A torque wrench to go with all of those
• Crankshaft holding tool, Audi #3242 or equivalent
• Camshaft holding tool, Audi #3243 or equivalent (these two tools can be rented from some parts suppliers)
• Two large buckets
• Safety glasses
• Big flat head screwdriver
• Channel locks
• Flashlight
• Camshaft sprocket puller (available at most auto parts stores)
• A small razor blade with a long handle ... I have one that's made for scraping window glazing that works quite well
• [insert your favorite method of lifting the car a few inches here]. Make sure it's a safe method (i.e. no cement blocks or foot stools)
• A spare mode of transportation is helpful, in case anything goes wrong an you have an emergency trip to your parts shop or mechanic.

Parts Required:

• Timing belt
• Accessory drive belt (why not; you're there, right?)
• Water pump
• Water pump gasket
• Coolant thermostat
• Thermostat O-ring
• Timing belt tensioner
• ~1 gallon of antifreeze (phosphate free antifreeze that is safe for aluminum engines)
• ~1 gallon of distilled or de-ionized water
• Rubber O-ring for the coolant drain plug on the engine block

Procedure:

1. Remove the big plastic cover that goes under the engine, then remove the bracket that holds the back of it to the engine block. You'll see a deeply recessed 8mm allen bolt at the back of the engine block on the left hand side of the car; that's the drain plug for the radiator fluid. You'll need the 8mm allen wrench socket, long socket extension, a large bucket, and your safety goggles now. Put on the goggles (antifreeze will spray everywhere) and get the bucket as close as you can to the plug. It's hard to get the wrench to fit in the hole where the plug is, but remember that it will be a lot harder to get the plug out if it's stripped so make sure you've got the wrench seated before trying. It takes a bit of work but it will come out. Get the fluid draining into the bucket, and then remove the radiator cap. Go inside (if your spouse will let you), wash your hands, and eat lunch while the fluid drains.
2. Get another bucket. On the bottom right (as you're looking at the front of the car) of the radiator there's a red thumb screw connected to a miniature faucet. That's the other drain plug. Put the bucket under the faucet and loosen the thumb screw. If it looks like the bumper will get in the way, you can stick a piece of rubber tubing over the end of the faucet and use that to send the fluid into the bucket.
3. At the top center of the firewall, there are two 1" hoses going through the firewall. One of them has a bleeder screw on top (sometimes ... in some cars this bleeder is omitted). Twist the screw -- it will break off in your hand. That'll be $50 because the screw comes with the hose. I was fortunate to have another plastic screw with the same threads (I don't know where it came from or what it was for, but it fit just right). You may be fortunate enough to not have this one break, but be prepared for it. Anyway, this is a bleeder screw -- loosen it to help remove more fluid.
4. Peer down behind the right side (as you're standing at the front bumper) cylinder head, and you'll see the coolant line that comes off the back of the block. It makes a 90 degree bend towards the middle of the engine, and just after that bend there's a sensor, and then a little screw with a big head (maybe 10-12mm) with a 5mm allen head on it -- this is the other bleeder. You'll want your long socket extension to loosen this. Only loosen it a turn or two, because if it falls, it will be immediately warped to that other dimention where socks that get lost in the dryer go, and you'll never see it again.
5. The following 4 steps are for small chassis cars only
6. The next step is to remove the radiator fans so that you'll have room to work. Trace the two sets of wires that come from the radiator fans to where they end on the body of the car. One set is bolted directly to the body, and the other set is bolted to a large metal heat sink. Use a 10mm socket to remove the bolts and free these wires. Make careful note of where they go! It's important that these don't get reversed, or the radiator fans will not work properly.
7. Remove the upper radiator hose from the radiator and push it aside.
8. There are three 10mm bolts that secure the top of the radiator fan assembly to the radiator -- remove them.
9. Pull the radiator fan assembly straight up to remove it from the engine bay.
10. Remove the first layer of plastic covers on the front of the engine to expose the accessory belt.
11. Mark the direction that the accessory belt is mounted unless you're replacing it -- if you put it back on, it's got to go the same direction!
12. On the tensioner for the accessory belt, there's a spot for a wrench. On pre-1995 cars, it's a 10mm allen wrench. On post-1995 cars, it's a 17mm socket. Twist the tensioner clockwise (pre-1995) or loosen the bolt (post-1995) to release the tension on the belt. Remove the accessory belt.
13. Remove the accessory belt tensioner using a 10mm allen socket.
14. Now remove the timing belt covers. There are metal clips on the top and bottom of each side. Start with the cover on the right side of the engine (as you're looking from the front of the car). Unclip, pull up, and wiggle them around until they either come free or break. If they break, make sure you get all of the little bits of plastic out! The bottom cover comes off last.
15. Get the 24mm (or 15/16") socket and twist the crankshaft CLOCKWISE (as you're standing at the front bumper) until cylinder 1 is at TDC. At TDC you'll notice that the oblong plates at the ends of the camshafts are pointing towards each other, with the big hole on each closer to the center of the engine. Also there's a little notch scratched in the accessory belt's main pulley that correponds to a little arrow in the plastic cover that's mounted directly behind it.
16. Crawl back under the engine with a flashlight, a 10mm socket, the flexible socket extension, your ratchet, channel locks, and the crankshaft holding tool. Look around the right side of the engine block until you see the crankshaft position sensor, which is mounted near the middle of the engine block, up and back from the oil pan. It's long and flat and has a big wire sticking out one end, and a 10mm hex bolt in the other. Remove the hex bolt, and pull the sensor straight out with the channel locks. Screw the crankshaft holding tool in where the sensor was. If it won't go in, probably the crankshaft is not at TDC -- rotate it so that the camshafts do a complete revolution and it should be ready.
17. Remove the 8 6mm bolts that hold the main pulley/vibration dampener on the front of the crankshaft. Remember that it's heavy, so don't have your feet under it.
18. Attach the camshaft holding tool.
19. Note the tension on the timing belt. You should be able to twist it 90 degrees without too much difficulty.
20. Loosen (don't remove it yet) the bolt that holds the timing belt tensioner in place. The tensioner will move! Don't worry.
21. Pull the timing belt off the tensioner, then off the crankshaft sprocket, then the other idler pulley. Loosen the belt around the camshaft sprockets and water pump so that it isn't mounted on anything.
22. Use a 24mm wrench to loosen the bolts holding the camshaft sprockets on to the camshafts about 2 turns. DON'T REMOVE THE BOLTS, just loosen them a bit.
23. Carefully remove the camshaft holding tool.
24. Use your sprocket puller to carefully release the camshaft sprockets. They are not keyed to the camshafts -- the camshafts have tapered ends that the sprockets are stuck on. When you release the sprockets (they will come off with a heart-stopping bang; don't worry! You haven't broken anything unless the camshafts moved) they will be able to spin freely while the camshafts stay in place.
25. Remove the timing belt.
26. Remove the power steering pump pulley (not the whole pump). This makes it a lot easier to get to the water pump. Now is also a good time to remove any remaining pulleys and tensioners that are in the way.
27. There are nine screws holding the water pump in -- remove them and pull the pump off. Then pull off the gasket. Haha! Just kidding. You can't pull the gasket off -- it's turned to glue and is stuck to the engine block. Get your razor and (carefully now) scrape the gasket off the engine block. Be careful to not get bits of it in the engine, and also be careful to not scratch the engine block! You can avoid getting bits of gasket in the engine by carefully stuffing clean rags or paper towels in the holes uncovered by the water pump. If you use paper towels make sure that they don't go in to far, so that they don't rip and stay in the engine when you try to remove them. Also keep in mind that the engine block is made of cast iron, so you don't have to worry too much about scratching it.
28. Follow the bottom radiator hose to the engine; it screws into a metal duct. Follow that duct to the engine block and you'll see two 10mm hex bolts holding it to the block. Remove these two bolts. 80/90, Coupe, and Cabriolet owners may want to remove the hose from the metal duct to make things easier to work with in limited space.
29. The thermostat might pull right out, or it might be stuck to the block. Either way, it's got to go, so pull and pry at it until it gives. Make sure that the lip behind the thermostat does not have a lot of corrosion on it.
30. The new thermostat goes in just like the old one was -- note that there's a little vent hole on the thermostat, which should go on the top. Don't forget the O-ring, which is attached to the metal duct.
31. Put the metal duct back on, and re-connect the radiator hose if you disconnected it. Note that the radiator hose has an arrow printed on it which corresponds to an arrow on the metal duct.
32. Align the water pump gasket with the water pump using a couple of the screws, and position the water pump on the engine block. Screw all of the bolts in finger tight. Make sure that the gasket is not sticking out too far anywhere.
33. Set your torque wrench to 10Nm (7 ft lbs). If it doesn't go that low, just keep in mind that it's not much torque! As you're screwing in the pump, don't tighten the bolts in order! Do one bolt, then skip 4, then skip 4 again, etc, until you've gotten them all -- otherwise the gasket will become deformed.
34. If you got a new timing belt tensioner, now's the time to put it on.
35. Loosely thread the timing belt over the camshaft sprockets and under the water pump.
36. Re-install the camshaft holding tool.
37. Put the teeth of the belt into the camshaft sprockets; then thread it around the idler pulley, then the crankshaft sprocket, and then the tensioner (last). Adjust the tensioner until the belt has the proper tension, then tighten it.
38. Tighten the camshaft bolts to 30Nm (22ft lbs) plus 1/2 turn.
    
    If you've made it this far, the rest of the procedure is fairly straightforward ("assembly is the opposite of removal") but I'll point out a few things:
39. Don't forget to remove the crankshaft holding tool when you're done with everything! Also don't forget to put the sensor back when you remove the tool.
40. Don't forget -- two drain plugs need to be closed before you add coolant! Leave the bleeder screws open as you add coolant until coolant starts coming out of them, then close them.
41. If you don't replace the accessory belt, be sure that it goes on in the same direction that it came off.
    

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