Quite some while ago, I bought an Audi A8 Quattro for what seemed like a good price. It was not a bad price, it just wasn't a good price after all. It's been a learning experience, which is automotive slang for I should have spent more money. I haven't become an expert by any means, but I've got a good overview of the vehicle, especially the engine. This is partly because I used Google to translate VAG1 SSP2 105, 161, and 162, which are "V8-Motor", "Audi A8", and "ABS 5 ... Audi A8" respectively, and partly because I've replaced both head gaskets. The following text is adapted from some text I wrote in response to an email question, which came in response to a post on QuattroWorld A8 forum. I thought it might be of interest to others thinking about doing a head job on the 32 valve Audi V8 Motor.
When I got the vehicle, the water pump was leaking, the heater wouldn't stop heating, and the ABS light was on and ABS was not functioning. ABS is also responsible for EDL3 so the car was fairly well crippled, although it actually still drove very well. It was also leaking quite a lot of oil. I secured documentation and began to resolve issues on the car, and things went fairly well until I got to actually doing the timing belt job and found that some holes in the back of the #2 head (left/driver's side, cylinders 5-8) were stripped out. I pulled the head, heli-coiled the holes, reinstalled it, and all that went well... but in the end, I still had oil leaks.
Eventually, after doing everything but replacing the upper oil pan gasket, I finally decided that I had to pull the bank 1 head. I had a damaged spark plug stuck in the #1 cylinder, so at least there would be a side benefit; I did manage to remove that after very little struggle by bashing out the ceramic with a variety of hardware, then running up the drill sizes until I thought the plug would be loose. Then I tapped a straight extractor in from below and turned it with a crescent wrench.
Note that unless you really think you know better, doing a head job on the engine also involves doing a timing belt job. There are many sources for that already, and I don't plan to even address that. Suffice to say that it involves a number of specialty tools, some of which can be quite spendy. It is difficult to get the lot of them under $300. You will probably need at least the Matra 3341 camshaft locating fixtures, to lock the cams into place after moving the engine to #1 TDC. They can, surprisingly, be had at a reasonable price from Snap-On Tools. The other tools can be improvised by the dedicated hobbyist, and it is probably possible to do the head job without them. You will have to decide how you will handle the issue of cam timing. The wisest thing is to perform timing belt adjustment. Regardless, before the head can be removed, you will have to remove the timing belt from the cam sprocket in question, and I will leave this job out of this article. Refer to one of the internet's guides on doing the timing belt.
The first step is draining of the coolant. You should not only drain from the radiator, but also utilize one of the block drains. Even a mediocre job of draining the coolant from the block drains will get the level below the bottom of the heads. You can leave the oil in the motor, but the coolant has to go. There is a valve on the radiator at the left side. Safe this stuff for later, it's spendy! There's actually no particular reason to use the special coolant, as the A8 was actually originally specified with the normal green stuff and then switched to the "long life" G12, but do not mix coolant types.
Air Intake and Fuel System
The second step is removal of the fuel and intake system and the intake manifold. First, remove the intake pipe, then the airbox, then the rubber adapter at the throttle body and set all of that aside. Disconnect the throttle cable and pull it out of the way to the right, and disconnect the cruise control vacuum servo from the throttle body. Disconnect all the fuel injector connectors, the coolant temperature sender connector at the front of bank #2, and the vacuum valve connections on the front of the motor. Now remove four 10mm-head bolts from the fuel rail and flip it over "onto its back" on the left side of the plastic cowl cover. Use some shop towels to gently wipe the ends of the fuel injector nozzles clean, then cover them with something (glove fingertips?) to protect them from dirt and damage. There's no need to open the fuel system at all so long as you keep the hood up. 4 If the fuel lines are cracked and/or leaking, they can be serviced instead of fully replaced; cautiously dremel off the crimps and clamp on some high-pressure, multi-fuel safe (to handle the ethanol content) 5/32 fuel line.
Vac System and Intake Manifold
Pull the crankcase breather hose off from the front of the engine and set it aside. Disconnect the vacuum system right next to the one-way valve on the way to the brake servo ("booster".) Now you can remove the four bolts and four nuts from the intake manifold and lift up on the manifold. It may require some prying, especially if it's been on for a long time; if so, the intake manifold gaskets will likely need to be replaced. They should be pliable rubber. There are two small hoses which have to be removed from the back of the manifold (actually from the elbow between the manifold and throttle body) before it can be lifted away. There are also connectors back there for the throttle position sensor and the intake air temp sensor, which are most easily removed at this time.
Crankcase Ventilation and Coolant Pipe
Now that you've got the intake manifold off, you can see the other crankcase breather hoses at the back of the engine, and get a good idea as to whether your ventilation plate is leaking. Each hose and the plate will individually run you a hundred bucks, as will the hose across the front of the engine. The left (driver) side hose and the front hose can be replaced with 18mm silicone hose. You will need a 3/4" elbow (e.g. from the plumbing store, preferably nylon but ABS is OK) for the left side hose. The right side hose is more convoluted and probably needs to be replaced with the real thing. The ventilation plate under the cover has a formed-on rubber gasket, so it needs to be replaced if damaged as well. After the intake manifold has been removed, you will also have access to the cross pipe which carries coolant between the heads, and behind the engine. This is held on with two 10mm nuts. The electrical conduit is wire tied to it. Once the nuts are disconnected from it, as well as one end of the small connecting hose to the pipe which runs forward under the intake manifold, it can be pushed back out of the way. It seals with two O-Rings. Replace them if they are old, or look damaged.
Valve Covers and Coil Packs
On to the valve covers. Remove the coil pack wires, then the packs, two 10mm-head bolts each. It can be tricky to remove the extensions which run from them to the plugs from within the head; carefully use long-nose pliers to grasp the electrode without damaging the retention clip wire if they don't come out with the coil packs. I like to keep them with the cylinders, but there's no difference between them when they are working. Then remove the valve covers; two 5mm hex socket cap head screws in the middle, and six 10mm head bolts around the outside. I needed to use a 1/4" drive socket on a 3/8" adapter to a wrench to access the one at the back on the exhaust side. Nothing else has clearance, but this actually permits my torque wrench to get on that last bolt. This is true of the cover on both sides. When you remove the valve cover, the rubber half-moon plug at the cam end may come out with it, watch out for that.
Do not remove the exhaust manifold from the head. This is a job in itself, especially while the head is mounted to the engine and the engine is mounted in the vehicle. There is no need to remove it. Instead, disconnect the three bolts which secure it to the exhaust system. These will have 12 (original) or 13mm (replacement) hex flats on them and be self-locking. They are meant to be replaced each time, but you can reuse them at least once if they are not rusted.
When you've got front covers removed and the timing belt sorted, meaning that you have removed it from the vicinity of the head after installing the Matra 3341 cam locating tool installed if you're doing that, and removing the cam sprocket from the head if you are doing that5 you can go ahead and remove the head bolts. You should remove them in the reverse of the tightening order, which is delivered with the new gasket, and loosen them in stages just as you would install them. This prevents warping of the head during removal.
You will need one special tool: an appropriate-depth 12mm metric double-square. You can get a kit of metric double square bits from Performance Tool very cheaply, model "W1395". You won't be able to use the usual long 12mm VW head bolt tool (used on the 2 liter of the same era, which has the same head casting!) because there is not enough clearance in the A8 engine bay. A normal depth 13mm socket will fit on top of the 12mm PT double square bit and leave room for a 3/8" drive torque wrench. You will not be able to remove the rear exhaust-side bolt from either head while the head is seated on the block. Leave it in the engine until you get the head out of the engine bay.
Now pry the head away from the block at the top. It should come free easily. If you are having to use much force, you probably forgot a step. Make sure nothing is in the way, and lift the head out of the engine. The weight is considerable, so you may wish to enlist a helper.
While the Head is Off
Before installing another head, clean any crud which has fallen into the combustion chambers out with a shop towel, and clean the head itself as best you can, Check over the spark plugs, and see what they tell you about how the engine is running on each cylinder. Clean the head as well as possible with a strong solvent, shop towels and a hard toothbrush, trying to make sure that nothing will fall out of any of the coolant or oil passages while re-mounting it. Clean the block face aggressively as well. Clean any other messes off of the engine which you've suddenly got access with a head removed. If you're doing the bank 1 head, this is a great time to do the oil cooler gasket, and perhaps install a Bufkin Aluminum coolant pipe, see eBay. The plastic pipe there is a frequent point of failure which leaks coolant from the right front corner of the car, and the aftermarket Aluminum replacement is a lifetime part. This job is insanely easier when the bank 1 head is removed than at any other time short of complete engine removal.
Installation is very much the reverse of removal, after installing a new head gasket. The gasket is market L or R, and the mark goes on the top side; it has holes for the dowel pins so there's no confusion as to which way it goes around. Switching the gaskets changes oil flow in the engine, and is a Bad Thing(tm). The gasket requires no additional sealant, only a clean and smooth sealing surface to start with. I would say the hardest part of reinstallation is lining up the exhaust manifold and the dowel pins at the same time. They are hollow, steel, and sharp so if you slip, you will scratch your head. On bank 1 you can remove one of the exhaust bolts from the manifold side, so you don't have to mess with those while you line it up, only the pipe. On bank 2 you may have to pull the O2 sensor to get the triangle ring out of the way.
Pro-Tip: That one bolt is a PITA
Stop here, though, and note my only real pro-tip: Put the rear exhaust-side head bolt into place before mounting the head, and put about a 1" spacer on it at the top to hold it up so that it doesn't poke out of the bottom of the head while you position it. Use a piece of hose sliced open as your spacer. Once the head is in place, pull the spacer out with a pick and the bolt will fall into position. You can't get that bolt in when the head is seated on the block. It is possible to tilt the head over towards center and weasel the bolt in after the fact, but it is not a good idea. Tilt the head up away from the engine until you have the exhaust pipe lined up and in place, then carefully pivot around that point and lower the head onto the block (and the gasket) while looking between them so that you can line up the dowels.
Torquing the Head and Valve Cover Gasket
Once the head is seated on the block, you may install all of the head bolts and snug them down, then torque the pattern (again, included with the OE gasket!) to 40Nm, then 60Nm,6 then turn all the bolts 90 degrees more, then 90 degrees MORE, following the pattern each time. There is even room to get a 1/2" drive breaker bar with a 3/8" adapter into a 13mm socket and onto the 12mm adapter to do your final 90 degree turns. Valve cover bolts and coil pack bolts torque to just 10Nm, or 7 ft-lb. If you overtorque them, they will strip easily. But if you undertorque the valve cover gaskets, or fail to torque the bolts in stages, they will leak. If the valve cover gaskets are not pliable, replace them. They come in a kit with the half-moon plug and the spark plug well gaskets, and are sold per-side. Once the head is seated, reinstall the cross coolant pipe.
Reinstalling the Intake Manifold and Fuel Rail
Reinstallation of the intake manifold is simple, just don't forget to reconnect the two little hoses or the two connectors back there, or for that matter to reinstall the coolant pipe and zip-tie the wiring back to it. Torque the intake manifold bolts and nuts torque to 20 Nm (15 ft-lb) and do it in multiple stages to account for compression of the gaskets, and movement of the manifold to the left and right during the process. Carefully guide the fuel injectors back into their holes (replacing any damaged O-Rings on their ends, which will cause vacuum leaks) and torque the fuel rail down to 10 Nm, then reattach the throttle cable and cruise control servo.
The rest of the process is either reattaching electrical connectors — you should know where those go, since you just took them off — or steps which are really part of the timing belt process. For instance, I removed the entire front of the vehicle, leaving the power steering and transmission cooler lines attached but removing the radiator hoses. This provides maximum access to the belts. It also means all of that has to be reattached afterwards, but the process is very simple.,
Performing a head job on the 32v Audi V8 motor is not for the faint of heart, but it is not an especially difficult task as these things go either and the process is well-documented in the official instructions. You do need a handful of special tools, but none of them are difficult to locate, or amazingly expensive. Replacement cylinder heads are regularly available for around two hundred dollars, so if something goes wrong with one of your heads it can be readily replaced. This is still a great motor even today, with its many forged components and incredibly compact packaging, and it's worth doing a little work to keep them around. For the enthusiast, complete motors becoming available under $1000 and additional components like bell housing adapters, oil filter relocation kits, an available ARP stud kit and other parts make them viable in motorsport or simply for swaps into other vehicles.
- 1. VW/Audi Group
- 2. Selbstudienprogramm, or Self-Study Program
- 3. Electronic Differential Lock, which uses the ABS to provide virtual limited-slip differentials up to 40 kph
- 4. If you're having problems with your hood gas shocks, make sure to prop the hood up properly before doing this so you don't damage your fuel system.
- 5. You need to remove the sprocket in order to replace the camshaft oil seals; you need to do timing properly if you remove the sprocket. As before, see a timing belt guide for information on this stuff.
- 6. 100 Nm = 73 ft-lb, so conversion is pretty easy if your torque wrench isn't dual-marked; just use 30 ft-lb and 45 ft-lb respectively