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My 2004 A6 Avant 3.0L blew white smoke during warm up and lost coolant. It also smells funny. It also has a P0305 code (cylinder 5 misfire) with engine check light on. The P0305 code was seen twice before in the past 3 months.

My best guess is the head gasket was leaking and is now busted at cylinder 5. I will confirm that with a snake cam into the spark plug socket later today.

Has anyone seen a write-up on head gasket replacement of this engine on the web?

Thanks

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Endoscope confirmed water in cylinder 5. I took this picture using an extra small 7mm diameter USB endoscope. Before using the endoscope, I notice the cylinder 5 spark plug looks cleaner than the others, yet another hint for future reference.

I am using the ElsaWin 3.6 manual and in the process of removing the intake manifold. Will submit a write-up when done.

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I finished the job and write-up on labor day. Kris promised to post the write-up under "Resources > Tech Articles" once he catches a break. Stay tuned.

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NOTE: Same Tech Article with pictures
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This job is to replace the left (U.S. driver-side) head gasket of an Audi 3.0L AVK engine in a 2004 Audi A6 Avant quatro. It is not a complete write-up, because I am referring to the ElsaWin 3.6 manual with my notes. For those who are Web savy, search "elsawin 3.6 torrent".

0) This job is done without removing the engine, without draining motor oil, without disconnecting battery. Follow the ElsaWin manual plus my comments, which may contradict the manual.

1) Drain coolant: Engine Mechanical/19 Cooling System/Coolant Draining and Refilling.

1a) No special tool is needed.
1b) Be sure to turn the coolant plug in counterclockwise direction.
1c) Due to clearance, it is impossible to remove the spring clip of the water hose to the oil cooler. I destroyed it with a disc cutter.

2) Remove bumper: Body/63 Bumpers/Front Bumper/Front Bumper, Removing and Installing

2a) I didn't remove the front wheels. I jacked the car onto two jack stands to gain enough space to remove the wheel house lining and get to the 6 flanged nuts (3 on each side) that holds the bumper.
2b) The two long vertical bolts (7 in the manual) will be used to hang the lock carrier later.

3) Lock Carrier: Engine Mechanical/13 Crankshaft, Cylinder Block/Lock Carrier, Moving into Service position

3a) No special tool (3369) is needed. Instead, use the two bolts in step 2b to hang the lock carrier.
3b) Place a sturdy cardboard box under the radiator to support the carrier and reduce load on the two bumper bolts.

4) Remove V-Belt: Engine Mechanical/13 Crankshaft, Cylinder Block/Ribbed Belt, Removing and Installing

4a) No specail tool (3299) is needed. Instead, use two wrenches in the picture to press down the ribbed belt tensioner. Use the 19mm open-ended wrench on the tensioner, and its 17mm side locks onto the 12mm close-ended wrench perfectly with no wiggle room.
4b) The tensioner is still compressed even without the belt, so remove the two lower (small) bolts first.

5) Remove In-take Manifold: Engine Mechanical/15 Cylinder Head, Valvetrain/

5a) I am only replacing the left head gasket, so no need to loosen the second air injection pipe and the right combo value pipe.
5b) Many plastic ties on wires and pipes have to be cut. I didn't replace any of them during installation.
5c) Wire plugs on fuel injectors were hard to remove in-place. I removed them after lifting the injectors up from the manifold.
5c) The fuel injectors were laid pointing up, to the right and on top of the battery compartment. Wrap the injectors in 2 zipper bags.
5c) Near the end of the instruction, it is impossible to loosen the last 3 hoses away from the throttle valve control module (the unit coupled with the black air guide by one long bolt). Instead, I unbolted and lifted the in-take manifold to a 45 degree angle supported with my rubber mallet (see picture). In that position, I disconnected the 3 hoses at the throttle module end.

6) Remove left/right head covers: Engine Mechanical/15 Cylinder Head, Valvetrain/

6a) Be very careful with the ruffled snap-on breather hose on the head covers. The plastic can become brittle. Gently ply on either sides of the snap ring while gently pulling it away.

7) Timing belt: Engine Mechanical/13 Crankshaft, Cylinder Block/Toothed Belt, Removing and Installing

7a) Special tool T40030 must be used ($85 plus shipping). T40011 is just a metal wire or long nail. No other special tool is needed, including the crankshaft locking pin T40026 (more on this later), which seemed impossible to reach.
7b) The most important step is to turn the crankshaft to top-dead-center (TDC) and install both camshaft locks T40030.
7c) My AVK engine does not have the "thrust washer" behind the harmonic balancer.
7d) When you ply open the camshaft cap, quite a bit of engine oil will leak out. I tried not to let oil drip down onto the timing belt.

8) Remove left cylinder head: Engine Mechanical/15 Cylinder Head, Valvetrain/

8a) Get special tool 3452 (T10070 in later manuals) for the head bolts ($9 on eBay). Mines came with a 3/8 female socket head that must be removed by striking the pin with a big screw through the head while placing the head loosely on a vise.
8b) Remove the snap-on breather hose connecting both head covers and the crankcase dome beneath the in-take manifold.
8c) Remove the back coolant reservoir hose connected to a screwed-on connector on the big metal coolant pipe. Then remove the screwed-on connector (don't lose its washer).
8d) Unbolt the left combo-value both from the secondary air injection pipe and the cylinder head. Move the combo-value with its still connected rubber tube to the right.
8e) Removed the left-side secondary air injection metal pipe.
8f) Remove the left forward oxygen sensor with a O2 sensor socket. Its wire plug is behind the small metal plate above it at the engine compartment wall.
8g) Step 8b to 8f are needed to disconnect the exhaust pipe from the left head. All 3 bolts of the exhaust pipe were removed from the top. I loose the top bolt with a 13mm socket from a go-through socket set, followed by a very thin and short close-ended wrench from an bygone BMW 2800. The two lower bolts were removed using the same go-thru socket set (see Combo Go-Thru Socket Set - SAE & Metric 21 Pc).
8h) The manual missed a spring loaded bolt that hangs the exhaust pipe under the car. Remove that bolt and support the pipe with a box.

9) Install head gasket: Engine Mechanical/15 Cylinder Head, Valvetrain/Cylinder Heads, Installing

9a) Use common sense. Try brake cleaner and soft rug first to clean both surfaces.
9b) My head gasket comes with a warning of not to use any sealant.
9c) Stop after tightening all head bolts.

WARNING: Do not follow the manual after tightening the head bolts, or you will missed the step to install the back timing belt guard plate. That metal plate and one bolt on the front coolant pipe must be installed before putting on the timing belt.

10) Back trace step 8 to install left cylinder head. Follow the manual and my notes in reverse order.

11) Back trace step 7 and 6 to install timing belt. Follow the manual and my notes in reverse order.

11a) I replaced the special tool 3387 with a $5 adjustable pin wrench for angle grinder with both pins filed down to 3mm (see Adjustable Pin Wrench).
11b) Since the crankshaft locking pin T40026 is not used, every time you tighten the timing belt tensioner or the eccentric pulley, the crankshaft may move. Note the direction of its movement and carefully turn the crankshaft back to the top-dead-center (TDC) mark in opposite direction.
11c) With the camshaft locking tool 3452 fitted perfectly, I don't see the need for tighten both exhaust camshafts using special socket T40028.
11d) If you install the ribbed belt tensioner in this step, bolt on the two small lower bolts first while leaving the top bolt and its housing out (bending the spring a bit). Then with gloves on both hands, press the housing into its hole through the timing belt guard.

12) Back trace step 5 to install in-take manifold. Follow the manual and my notes in reverse order.

12a) Clean both the injector heads and their holes in the manifold with Q-tips soaked with brake cleaner.
12b) A silicone spray works wonders when inserting rubber hoses back onto metal or plastic pipes.

13) Back trace step 4 to install V-belt. Follow the manual and my notes in reverse order.

13a) If you install the ribbed belt tensioner now, see 11d.

14) Back trace step 3 to 1 to finish the job. Follow the manual and my notes in reverse order.